The Complete Android & Kotlin App Development A-Z Bootcamp

1. Introduction: Hello, I am Humerus, and welcome to the complete Android and Catlin app development two Z, Woodcomp Court. This is a course where you will go through beginner's level with simple projects and reach professional levels with more complex and realistic projects. All you need is to be persistent and try this course every day. On each day of the course, we go through a learning cycle length, practice together, recap together, and do a quiz together. If you don't like quizzes, don't worry. Every quiz will be answered the next day. But I insist that first you try to do the quizzes and exercises by yourself so you can learn more. During this cycle, I try to explain everything in different ways, so you can learn by the simplest way as possible. If you don't get something in the very first video, you'll get it through entire course because we will get back to everything and subject many times to make sure that you understand all of them very well. During this course, I will also teach you all the tips and tricks that I have acquired over the years of my work experience as an Android developer, fullstack developer and project manager. You will pay attention to your Android application both from the developer's point of view and from the management point of view. 2. Day 1: Install JDK & Android Studio: Hello and welcome, let's install. First, we should install JDK. We search for Java JDK. First link, Java downloads in Oracle website, we click on this. We'll go to this address. Joa downloads. Joa downloads. Last version. You have previous version, as you can see, but you want this last version. I don't have linux. I don't have Mac OS. So I don't need those. If you have these things, you can install them. But I have windows. So I click on windows. We have 64 version. So, which version should I in at? Simply on this PC. I right click on empty space, for example, in here. You see, not on the fools. In here or here, on empty space. And I click on properties. First, you can see I have windows ten, and then on system type here. You can see. I have 64 bet operating system. So I have 64 bit. Let's come back to Oracle page. We have 64 bet in here as well. So we download this I right click on this and save Link, and I save it on my desktop. On the desktop, I already save this. What if you want, you can press save. It takes a few minutes to download it. After that, it's finished. I also download the Android Sudo. For that, I search Android Studio on Google. I see, we have this developer that android.com, and we click on it. We're on Android Sudio Site, and simply click on download. We have this page. We come down and accept this agreement. Of course, after we read it, and then we can download the app. We click on this and this starts download. After it finished, we also have this Android Sudio in installer file. This phone. I have the files that I downloaded on my desktop. First, we install JDK. We should double click on it or right click on, click in astall. Let's double click on it. This is the installer guide. We simply press next. This is the location that ova install on your system, ova development it, as you can see on the top. I accept this default location, press next, and it starts to install. As you can see, Java development kit successfully installed done. We write CMD because we want to att command prompt. We write CMD. We have this command prompt. We can click on it or simply press in. We have command prompt. We write Java space. Where en and press inter. What do we have? We have Java version 22.0 0.1. So we successfully install Java development kit this JDK, and we check to be sure we did it right. So now we can be sure we install JDK correctly. Let's go to the next level. I should mention, you should first in install JDK, not Android Studio first, JDK, and then Android Studio, right click, run as administrator or double clickon. Let's do this way. Or double clicon. Okay. Next, what we have here, checked. This is checked Android virtual device. What is it? Virtual device for testing your apps before exporting that APCs for the real phones. You can test these virtual devices inside your computer without any phones, just with your computers. So how much space do we need? So we should have this much space on our computer as well. Of course, in the future, we should add some other things. So be sure you have enough space on your computer. Maybe at least 50 gigabyte. And I think it's better. You do this on your CD dive, it's really easier. So you should put aside about 50 gigabyte on your CDI for this. And I also recommend SSD instead of hard drive. I think it's better to mention. Okay, press next. Where should I in a cL? As I say, I think it's better default locations on the CD dive. It's easier because without any thing to do, All the other things can find each other. For example, and you easily find JDK because that JDK in the default location or the other things we in the future add find all the other requirements. Anyway, longest story short, default locations is the best and be sure you have about 50 gigabytes at least on your SST, better than hard drive. Next. And what should we call it on your start menu? And read you, of course, I don't change it just in a stall. We've wait a few minutes, so this is over. It's based on your computer speed, maybe more than a few minutes. Since I have SSD, it took about a minute or less. Next, and start. I don't have come fi so do not import setting. Press. I think it's better to send usage statistics to Google to help to improve Android Studio. Android Studio, find available SDK components for us. As you can see, said welcome. Just press next. How do we want to set up our Android studio? I think typical thing is better. What it's right? What's the best things. Many of them they choose for us. Press next. I said, We do these things for you. Is it okay? Said if you want to review or change any of your installation setting, you can go and say, I want custom. But if not, STCs and other things we install them for you. Anyway, all of these things is good. Just press next. Accept to all, I should accept the license and finish. It starts downloading. Well, our installation completed these components are downloaded and installed successfully. So now we can press finish this finish button. Now we have Android Studio. And Studio welcome page. In this page, we can create new project, open project, and the other things. We have this more actions. Press SDK Manager. As we can see, we installed STCs and we have this appearance and behavior on the top. We click on it. We have this new UI. We checked the Andrew studio checked enable New UI by default. We don't change it because I think new UI is better. It's really better and also in appearance. Our tm is dark. We have other things. You see light. Light with light header, Dracula, and high contrast. I think dark is good. It's good. I use dark most of the time. So no changes in here, but I just want you to see, we have this appearance, we have this new eye, and it's good by default. But if you want, you can change this to light or any other thing. I prefer this one because it's better for my eyes at can see we have this virtual device manager. And we say allow access, any public or private network. We have this virtual invoice in here. If we want to create new virtual voice, as we can see, we have already one because we say and read the studio do all of these things for us. But if we want to create new one, we click on this plus button, this this Plus button, create virtual voice, we click on it. On the left, we have phone tablet, desktop TV, and even OS like watches. We can pick one of these and then press next, or even we can create new hardware profile and have a custom hardware profile that doesn't exist on those things. And we cancel. And when we find which one of these things we want, we press next, Anyway, I just cancel it. And this is virtual device. Now, it's time for our first project. I should just say in the next video that recorded a few months earlier, I show you how to create new projects. But for now, since I saw Andre the Sudio from beginning, Why did I do that? Because Andrew D Sudo in installation changed a little bit, and I just want to show you the latest in installation, how the latest version of Andrew D Cdio, installs. Because of that, I recapture this video open. In the next project, you can see the new project, but since as I say, it's a few months anyway. I just want to show you when you press okay. And, you ask, Do you trust this project? Do you trust this source that you are opening? I just want to show you this. We can press this trust or we can preview in safe mode. You can choose whatever you want. Since it is my own project, I created myself with you guys in the few days in the future. Lessons. I just press trust project, and I can check. I trust the project in this location. Don't you need ask me these things? I trust this location. And I press trust because it's my own project. And that's it. Thank you. And in the next video, we create new project together. 3. Day 1: Create First Application: Okay, we can open Android Studio by double click on it. Now we want to create new project. Our first project, we click on this button, new project. We can see a few templates in here. We can choose any of them. These templates are some small applications with basic codes. For example, we have basic views activity with this plus button. And also we have other things like navigation activity or button navigation view activities. All of them have activities and simple codes on them. If it's so many different templates to you, don't worry, we make sure. So in this course, you can create most of these activities and templates yourself an activity. As you can see below each of these you can word activity. Activity is simply call as a page, but it's not exactly look like a page. We can be more specific later on the course, but for now don't consider activity as in a pages. For now, we start with empty activity. We click next or double click on it. You can press previous to go back to previous page like this. When you choose empty activity, you can press next or double click on it. Okay? You have name. This name that will be shown in the Android launch for this application. What do you want to call your app? Just remember, when you install it on any phone, you can see this name, this name as the name of your app on that phone. This name must show what is your app. So I call my application capital Y, capital H, and I say hi. Now, package name. What is package name? I think in many ways to explain this, but the simplest way I can explain it to you, the simplest way, imagine each house in your town has a unique postal code. Two house with same postal code can be found. Why? Because if we found two houses with the same postal code, how can the post office make a difference between them? The post office can decide that this parcel belongs to one of them and the other belongs to the other one. Anyway. Long story short, each house with each postbox has unique postal code. Never two houses have the same postal code. This is long, but I think I can make my point, and I hope you understand what I'm saying. Package name is the same thing as that postal code. It shouldn't be duplicate. Okay, Andrew, the studio, add my name application name at the end of the package name. But it has other parts that separated with dots. For example, I can put my domain name in here, 7204. Okay, We see this error at the bottom. A digit cannot be the first character in a package statement. What should we do? This is my site. Since this is my website, I want to this be at the first of my package name. I have.com I first write the com, then my site is seven x 24. This is extra 7204. And my application is say hi. This package name is unique because it starts with my domain name and ends with my app name. Say hi. In case of my problem that your domain name starts with a number, how should we fix? Because it happens from time to time. You might have the same problem. Well, let's write under line before seven. You see the character under line cannot be the first character in a package segment. So I write site, my package name is com site 7204 layer, say hi. It is unique because no one else has a site with this name at the end of that site. Because I want to make a difference between my apps I write, say hi. I can understand this is the application, it's the say hi application. Since this course starts from basic levels, I will try to explain everything as simple as possible. It will be a bit time consuming, but you will learn all basic concepts very well. Anyway, as I say, this is unique. And later on when you publish your app on the play store, Google and all Android devices, know your application with this package name. Some of Android tutorials might say to you, if you don't have a website, say for example, write example in here. Never do that. You can use your own name. Your first name, it's okay. You can use your company name, you can use anything. But please never write example in here. It's not right. For example, if I don't have any, I write not my last name, but never example, Okay? Enough of package name. Let's see, safe location, this is there. Your project will be saved on your hard drive or state when you want this project to be accessed again, you should use that place, name it right by default on the folder Android Studio project. The Android Studio create a project with the name, Say I changed the location. Okay. Let's press this button. This is the folder that Andrew Studio, by default, selected for me. I changed it to Desktop. Can you see this small arrow? I press this so I can see the other folders. I folder name, Projects. I click on this, now I can save it. On my Projects folder on my desktop. If I press the arrow beside the projects, you can't see any other folder because it's empty. You can see this is empty, okay? But it's better to have an folder inside that project folder so I can find my project between other projects. Okay. What is the spot? I have home directory, I have desktop directory, I have new directory. I want to create a new folder. Now Android Studio asked me what is the name of this new folder name? I say zero under line, say capital, say hi. This is my foll. Now I can press okay. Or press in Android Studio, create A with the name, say hi for. You can see it. This is the F that Android Studio creates for me. I press okay. And you can see the address on the top. Okay, This is my address. All of my sources say in here now, minimum SDK. What is it? It's the lowest Android version that can run your application. Your application can't be installed on the lower version. For example, if you had your Android PK, you can't install it on Android six because minimum SDK is Android seven. So you have to use minimum Android seven to install that app. You can read, your app will run on approximately 96.1 of devices. It means 96.1% of all Android devices that recognized by Google Play Store have Android seven and above. About 2% 0.9 of them are Android six and below. If you change it, for example, let's say Android eight. Now your app will run on approximately 93.4% of devices. For now, Android seven is okay. We can have a version of Android, but they are outdated and I don't want that. Maybe you use some new features of Android doesn't exist in a Android versions like Android seven. And because of that, maybe you want Android eight on Android Noi. But be careful, if you, for example, use Android Noi, about 14% of devices can't install your app. Anyway enough of this. We chose that Android seven. Okay. Build configuration language. We have three options, but we continue with recommended Catlin. Maybe on the course, we look at the other options as well, but we stick to the recommended language. If you have older version of Android, for example, a few years ago in this place, you can also choose Java for your app. But as you see, you don't have Java. You only have cutline and groovy anyway. I leave it with recommended. Okay. Everything is good. We discuss all of these and explain them. Let's press Finish. It takes about ten to 20 seconds. So my project Create, and as you see, my Radial is going to download some files and some packages for my project. Okay, it's finished. It takes about one minutes for me. We'll continue the rest of this project in the next video. 4. Day 1: Checking The First Project: Okay, we came until this far and we just start our new project. Our project doesn't have activity underline. Mame if you are a little familiar with, and you might wonder there are layout files. You look for them in the project folder, see the files, and you can't find it. It's okay. I'll show you what happened first. Let us see what do we have here. We have our follo, our package name, and under the main activity dot for Catlin file, the file extension is kt. Okay. Inside that file, we have a few code. Let me quickly see this. And then we will look for the XML files. We have package name. This is the package name that we defined when we were creating the project for the first time. After that, we have this import. We have this arrow. If you open it, we have a few imported libraries. For the first time when you create a project in Android Studio, it needs a few packages and files to download. Depending on your Internet connection, it may take one to 10 minutes to download all necessary files. Just be patient anyway, You don't need to worry about this part right now. We will cover all these in future videos. Let's take a look at the main parts. Here we have the main activity as with a function called and create that runs every time you open your app on the phone. In this function, another function greeting is called to which a string value is passed. For example, user. You can change it to anything you want. In here we have this function as well, name greeting, and it takes a string inside it, we create a text for that text that we create. We set an attribute, attribute text with the value, say high. Do you remember the name? Say High. Whatever this name is. The say high 999. I wrote it, this 999 after it and I change this text. Don't worry about these commands for now. We'll cover them all in the future On my app with this button on the virtual device that I added to Android Studio in the previous videos. After some time, my app will open in virtual device as you can see. Okay, I'm waiting. Okay, it's ready. I can see in my visual voice that is pixel L P 34. I can see this, this is my pixel Cel API 34. I have a few other buttons, I cover them later. If I zoom it, you can see say high 999 as you see inside the text, because I create this text and inside that I give it a text with the value of say, high name. The name is 999. I have this. Let me this. Okay. And zoom a little bit. If you make an APK file off your app and install it on a real phone device, you will see the exact same output as you see here. Like this, it means whatever you see on the virtual device, it's a preview of your actual device. You all users phones, you can test it in here first. Okay. Now let's try to find the XML files where our layout should be. As you remember, we create our new project from temperate. You can choose file, new new project to create new project, to create this empty activity project. But something you might not know, this logo is for composed, the project that we made. Some experienced programmers do this mistake, as I see in the past few months, some of my own programmers do the exact same mistake. Why? Because it's on the top and it seems healthy activity. But it's composed. What is composed? Compose is a new way to design layout for Android apps. You create objects and items on each application page using Catlin language. Compose is good for large apps with many pages. And as the very first part of this course is in beginner level, we will continue with Mal layouts, but we come back to compose in future why I chose this format. In the last video, I wanted to show that you might do the same thing and get confused. Even some of the experienced developers I work with had done the same thing. Then this new version of Android Studio was released and didn't know how to fix the problem. During this course, I may do the same by making deliberate mistakes, so you can learn from them. If you want to create an application with X ML layout, select the empty use activity. Okay, Press next. Let's name the application I write, say high with main XML. I want to say that this app is using XML layout. Of course, it's not a good name. You shouldn't write like this. You should write the name, Whatever your app actually do, user can find it with this name. Anyway, package name. I leave it because it's just a test language minimum SDK. I cover all of these. I don't repeat them. Finish. Okay, now I create my first project, but this time with XM layout. We will continue with this project and start coding in the next video. 5. Day 1: Completing The First Project (Part 1): Okay, I just reopen my project in Android Studio. I see this tip of the day. You can check this tip of the day. Don't show these tips on startup, but I don't check this. I never check this. Why? Because these are useful tips. For example, let's read this tip. Convert Java classes to Colin. You can easily convert any Java class to with the same semantic. To do that, select code. Convert Java file to Colin file from the main menu. Anyway, we will cover this in the future. Okay, back to our project. We have two foil, main activity and activity XML inside each of them. As you see, there are some codes as well. Inside the there's code. Of course you can see how does it look like, but they both have some codes. You have these codes in both of these files because you use templates. If you create an empty project, you don't have anything and you should create from zero by yourself. You can build your project any time from this menu, Build, Make Project. When you press it, it takes a few seconds to a few minutes to build your project. If you have any errors or problems, you don't have this screen check and you have those errors. You can see your building process in this window. And when you even press this Run button to run your app and see the result, you can see in this window, how is the building process and what is going on, okay? Let's minimize this window. You also have this resource manager that all of your resources are here. For example, even your colors are here and strings is here. You have your files. As you have your hard drive, you have them in here. For example, this main activity, you have it under that folder. Any time you lose it and you want it again, you can't double click on it and open it. All of the other files in here, you can access them In this project window, you have all structure of your project. All project file that you have are in here. You can see all of these files on your hard drive. For example, if I write, click on this and open in Clare. I have this on my hard drive. Okay? I open the app, I have the SRC. I don't have them in here. Why? Because I should use this drop down and change it to project. Okay. Now now I have the same structure libraries and SRC in here as well. If you want to see them in here, you can see under the Fuller libraries RC for the source exactly the same. You can also change it back to Android structure that categorized them as recommended. Not exactly the same on your hard drive. Anyway, we stay with Android view, we have all the other views as well. We stay with Android view because most of the programmers use this view. It's easier to understand and easier to use. Okay, long story short, we have this file and this activity, that XML file. Cutlin code is our programming code that we defined what happened if anything else happens. For example, what if user click on something, user enters a certain page? What if user do anything else? But in XML files, we define how should the app look like. For example, you see this is how our app look like at the moment. A text with amount of hello world at the middle and a big wide screen. If we have an APK file and in a solid, on an Android device, even not a phone, we have a screen. A text with hello world. We can even change this. You see all these XML text. We can change all the attributes of the texts. For example, we have text inside that Android hello word. Don't worry about the other things. We explain all of them and many other things in the future. But for now, for the simplest way of have an example high with capital there. High there. Okay, Let me back to preview page. You can see now I have high there like this. I changed the text. If I change this text, I can see it on my app. But what if I want to use the click on a button and after that I show different text. I can't do this inside. And ML, I do this on cutting inside here. I say if a user click on that button. So change that text to something else. This is the difference between XML and Cut Ling. I hope you can understand what I'm saying. In the future. I give as many as possible examples, you can understand it completely. Well, before I forget, if I have some resources, for example, images, for example, some texts for different languages, for example, pictures or anything else. Do you see the resources full inside that you can have all your resources. For example, if you have some kind of text or even defined colors, you can put them in here. You have the color emer file to name your color that you want to use in different parts of your app. For example, as you can see, you have these color name black with this amount, you can see Preview on the left. This is color black, color white. With this amount you can see color white. Preview also a string, you have your app name here. You can also put all string values that you want to use all around your app. For example, some for your buttons or anything else. I hope you can understand it for now. Let's move on. Besides these values, let me quickly show you your app icon will be saved in map. As you can see, your app layout file will be there in layout folder. As you can see many other things. As I said before, I forget from time to time you might have some errors, but there's nothing wrong with your app. I might say this a few more times because it's important. You just have to came inside, build and make your project again. Rebuild your project. You can use make project or maybe rebuild project, whatever that works for you and you might have no error after that. Sometimes happens, but not all the time. 6. Day 1: Completing The First Project (Part 2): '. Okay, let's continue. I want to add a button to my app like this. I want this be below this text. And at the middle I connected to right left. And this text I also, you can see this attribute in here. Open this attribute from the top. I add 50. 50 is good, Yes, and you can see 50 DP margin, top 50 DP. Let's find out what is DP dimensions in Android Studio. What is dimensions? Dimensions value defined in XML or layout files is specified with a number followed by a unit of measure like this. What do we use it for for distances? For example, in here, margin top equals 50, it means you should add a margin top for 505050. What is DP? Next slide, we continue to explain this. We have different measurement units to define size and distances. As you see, we have pixel inches, M, M millimeters, T points, P density, independent pixel, and SP scalable pixel. But the most used ones in Android are DP and SP. You can read the descriptions for more information, but which one is better for what anyway? Recommendation use P for text. Use DP for other dimensions and sizes like margin, weight, height, and other things. Let's know more about DP. If you have two devices with the same resolution but different screen sizes, for example, 5 " and 7.1 ", the density in the bigger screen is lower than the smaller screen device. Because of this, if we use DP for an image size, that image will be bigger in the bigger screen, but in the smaller screen density pocket. All screens are grouped under density pockets. Mdpi and others that we can see in Andre Studio. You define what screen, which of these pictures. I think again, it's intermediate. You can came back here in the future if you don't understand any of these, even when you want to put your icon in your app, there are sites that you can give your picture in them and they give you all these sizes. Even then if you don't understand exactly which picture for what they create for you, all of these things, this table as you can see. You don't have to remember all of these numbers. These are for more information to know about which size is better for different screen sizes and what is the actual size of same image in different DPI screens? Nothing. You don't have to memorize all of these things. Don't worry at all the images except app icon stored in drivel folder in Android Studio. As you can see, we have these sizes. Again, recommendation always provide all density buckets for all the images that you want to use in your app. What does that mean? It means if you don't have some of these images in one of these follers closes, size is found and used. What I make it clear if you don't provide one of these pictures, it goes to nearest folder, for example, if you don't for white this, it goes here. And look at this, you don't put it here. Okay. Go search in here. Then it find it in here. It resize itself because the Android resizes by itself. The quality damage. It's not the same as if you do it yourself. Because of that, it's better provide yourself. You will learn more about these things during this course. Don't worry about it. But for now, because we want to clear what is DP or other thing, we cover all of these things. I said it again, don't worry at all. As I noted here, density pocket name will be at the end of the related rival filler. You can see at the end of each of these. That's it. Let's go back to Android Studio. Okay, I have a ID. What is ID? It's the name that we call our object. For example, if I call this button PTN, say it said, what do you want to do? Every place that use your button, you want to change them with BTN. Say I say yes, for example, Delete that high. It also said, All Peace, that uses your button and say we use it with the name BTN. Say hi. Do you want to change it to BTN? Say I say yes, because all places inside the app known this button as BT. And now I changed the name, so they should know about this. I changed it all places, press that button. We explain more about this window in the future. Okay, we changed here. Now if we see in the code, you can see this button ID is equal BTN, say hey. Now I can see this text is button, I want to this text say hi to us. There you can see it's changed. I want you to see. You can change it from this, from here I changed the idea. And also from this place code, you can see that the I just changed inside the T. You can change it in here, but I want to see you can do it from the XML view, text view. Okay? Okay. Now, what do we want? If I click on this, say hi to user, change this high user to different texts? How should I do that? I inside XML file. As I told you, we need to do this kind of thing. If I click on some should happen. This kind of things I should do inside file file, okay? Okay. Now I want to say something. If that pattern clicked here, I want to execute some code for that inside out pattern. We have this attribute click. I write the name BTN Clicked inside this lick event. But it's under the attributes. Anyway, attributes or event. Let's continue. You can see this click inside this code. You can see this here. What does it say? Say you don't have this method inside your cut ling. Okay, What is the suggestion? Create this inmate activity. Okay, let's create this Android studio created for us. Inside it, you should write some code. Okay, let's create a variable. Variable, it high, that is a text view. Tens inside the widgets. Create a text view as type of text view. I should feel it. Find view, I find view ID. I should say which object is belonging to this variable R. R stands for resources ID. As you can see, I can see all of them text high. Okay, now we want to do something high. What should we want to do? We want to set what you want to write. Finally, say hi for the first time, we say hi. As you can see, you say this yellow line. It's because we can do this in many different and better ways, but we just want to click function so we can write our first. Okay, let's run it. Okay. Our app runs about, I think, one, 15 seconds or one minutes later. You can see we have this button, and if we press it, we finally say hi. It's enough for now, because as you can see, we have many other things to talk about. For example, we don't know how to create variables. We don't know what is function, how we find these things inside resource, why this warning is here, and what should we do, and many other things. In the next lesson, we should start with basics. We cover basics one by one, and then we came back for more complex programs. 7. Day 2: Day 1 Quiz Answered: Okay, let's answer our Thursday quiz. Question number one. What is the best installation order for the following necessities to act development in Android Studio? We have CK, Android Studio, and JDK. Since we in previous video in day one, we have first our JDK, then Android Studio, and then SDK. Very easy. Question number two, why do we use emulators, of course, to preview our apps before we install it on a real devices? This question number three, when does the event, I'm sure you can say this easily. When we click on a object in a page, the click event is called. For example, if we click on a button, as you saw in previous day, we use this click event to change a text. We can use it in many different ways, but of course you can first define what do you want to do. 8. Day 2: Create the app (Empty Project): Welcome to day two project simple calculator. What will it do? Our calculator takes two numbers, does four main arithmetic operations, plus, minus, division, multiply, and show the result. If I enter one number here, one number here, and press any of these four buttons, the result will be here, East. That what will you learn? You learn at least these four things define variables, different data types in Cutlin, operators and conditions. Since we're on a project, we're creating this project, you will learn many other things that will come up as best as I can to teach you many small details that you might find very useful. I hope you enjoy. Okay, let's create our first project. When you open Android Studio, it may open the latest project that you were working on it. If you don't see this window, you can simply open this menu file Los Project. Now you can see this window in this window. You can press this button. New Project. Okay, This is your template window, the window that you can choose, any template. Anyway, On the left you have the television. But we chose phone and tablet. You have some templates in here. Each of these templates have something for you. For example, template have a back, this template have a back button. And this button in the first, we have this because we want to do a different thing. We start with no activity. We create one project with this one project, and now it's time for no activity. Let's see what we have here. We press next or double cconet. Okay, We should write name. Okay, I write this name for my calculator. My calculator, this is my project name, package name. I write this honestly, the Android Studio write it for me because I write these things before. And since my name is my calculator and Studio write it, I didn't change it. As I said, it's a unique thing. This package name, like your phone number or your postal code. I said this also in first day save location. My project saved, as you see name my calculator. Since I saved my previous project in projects, the Android Studio. Yes, I want to save it in my calculator on the project. As I say, my last project in there, language cling why Catlin because Google Android Studio suggest Catlin is better. I chose Catlin for my project now, minimum K. My minimum K is Android seven. I can't install my app on device if it has, for example, Android six. All the Android after seven and Android seven support my app. And it's about 96.3% devices. It's a good number. Anyway, configuration language. Since do recommend this, let it be this and finish. Since I just created my project, we wait for a few seconds to a few minutes until the gradual build my project. Okay, my app bill is successfully completed in 1 minute and 5 seconds. As I said, it might be different based on your Internet and computer power, like Ram or CPU. Okay, let's continue when your project is ready, let's see, what do we have? We have two main part in the project. This project that we can close and open, and this main window that we have in the center. We write all our coding in this place. In this main place, the project section that we have in here, be sure that you select Android for better access. You also have this project view that shows your project the way that stores on your hard disk. Anyway, we cover all these things on the first day, Okay. In the Apple, these three pollers manifest, Catlin plus Giova and resources. In this Catlin plastiovo, we have this holler, since we didn't use any template, it's empty also. We have these resources. We come back here later. We cover some of these things in first day, we want to add a new activity. We continue this in next video. 9. Day 2: Add an Activity in Android: Okay, welcome back. Adding activity to our project. If you're not seeing this like this, you can choose option three. Appearance compact medial packages this. Don't you see this? But if you check, you see like this. Okay, let's move on. Right click in here. If you have like this, right click on the last one. New activity, empty Activity click. Okay, you have this. We are now adding an activity. Let's look, what do we have? What should we call it? Let's call it Main activity because it's our first activity and its main activity. Actually, each activity has two part. The part that you type your, the layer that you see, we call it layout. Because of that, you have two names. Mostly you have the same name. You can find which layout belongs to which activity, you can find one while looking to another. You see there's a different, slightly different in the naming. Be careful, you can't write any space in here. Layout name is not set to a valid resource name. Space is not a valid file based resource name. You name only contain lower case a to Z and number zero to nine or underscore. That is this, you should name it as it should be, not anything else. For example, you cannot put a.in here. You can't use capital like this because of that. As you can see, you have Big M up there, but you have a small characters down here. Okay. What is our package name? Our app package name, Of course, what our language for coding Cut. You can also click on Job. In this course, we use Cutlin, but we have also one other thing. You see this launch activity. What is this? Then you click or touch, let's say touch on Android voice. Then you touch an icon in your Android voice and launch an application. You have a default activity. Every app has a default activity that you see when your app open. If we check this launcher activity, this activity considered as launch activity as default activity. We check it because it's our main activity. Okay, nothing else. Let's finish this and wait. Our activity will be created. Now we have this main activity at this activity on the line XML that, as you can see, has our reviewable activity. This is our main activity, Katie and XML. Before I forget, let's change it to compact, since I just like to disk you. What happens if I close this and I close this? How can I find them? First project then, Not this android view, The clesva, my package name, main activity, double leak. This is K has my code. Then under this resource, I have my layout on this. I have my activity main XML. Okay? I have this manifest up here. Inside that, I have this Android manifest XML. The easiest way I can explain about this Android manifest that M. This is our foundation. It is our base file, the most important file. This XML file contains important metadata about your Android app. This data includes, for example, package name, activity names, what is your main activity? And lots of other thing. Long story short, it's the most important file in your project that everything starts from here. We have lots of things to do with this in the future. For so many reasons, we will come back to this. But for now, let me explain some of them. What is our app? This is our app. What do we call it? What is my app name Or what is my team? But we're not here for these things. We're here for this activity. Every activity that you add to your app has an entry in here. All of the activity in here, for example, we create an activity, we have it in here. We activity that we added its main activity. We check it in just a second. Let me continue with an example. Right click in here. New activity, empty activity. For example, I create an activity named logging finish. Okay, I have this logging. Let me back to this. As you can see, you have this name logging. This is the whole code that inserted in our Android Manifest ML, the three lines, the name and exported. Before I forget, you should always start your activity. It's the rule. It's not forced by Android Studio, but it's the rule. New activity and empty activity here. Always start capital letter. It's important as you can see capital M, capital M in here. As you can see, capital capital, it might has many parts. For example, main with capital and activity capital also each word with a capital. Another thing you can see login, Since we have one login for our code, we have this activity with our viewable part. Our layout is here. Activity naming and layout naming routes. Let we see what do we learn until now. Activity name, we start with capital letters. If you have more than one word in your activity name, it is better to start each word with capital letter for more readability. For example, activity logging activity, Can you see the capital A capital The word Activity at the end of the activity name is optional but but recommended layout names, you can only use lower case letters A to Z numbers zero to nine. And underscore in layout names, white space is not allowed because it's not in and all the other characters. The name of layout file should be the same as related activity. For example, main activity activity, you see the relation, you can see more of these things in the future. We explain all of them many times until we can be sure you understand all of them. But this is a very brief explanation of what we are doing in the future. Okay, let's go back in many. First, as you can see in here, we have just these three lines. Why? Because we don't have the launch. Our new activity isn't our our main activity. What if we want to change our launch activity? For example, I want this logging activity be the first activity that everyone sees. First, we close like this. And between this part, as you can see, this intent should be between this and this part. We cut it. The control X, and exactly in here, we pay control in here. What do we have? We have this red under line. Why? Because a launch activity must be exported as of Android 12, which also makes it available to other apps. If we make it, the error will go and your login activity will be accessible with other apps. Anyway, I hope I can explain it. Well, let's change it back to here. And also, we don't need our logging activity, let's just remove it. We delete also delete files, this login, we can delete it from here or just press delete button safety, delete search. Okay, of course. Okay, delete anyway, because we don't use it anyway in anywhere, this activity login. And also press Delete, and of course, delete deleted. We will continue this in our next video. 10. Day 2: Create Layout - Part 1 (Constraint Layouts - Edit Text): Create layout part one. Okay, Let's continue where we just left. I just checked my videos and I think my funds might a little small. I should make them bigger for that, I choose. May you file this setting? As you see, the short card key is control and at the same time I search for the fund. In here I can see first I have this appearance. I make it out 16 apply. It makes the whole app a little bigger. And the editor for my co part, I have the fund here as well. I think maybe, let me see if I give it 15. No king, how is it? It is really good. It's better. I think it's enough. Okay? Okay, I hope it's better for you. And you can easily read this. Okay, let's continue our coding and project. Okay. First, close this and let me see if we run the app. We should see our activity on the line main ML, we first our emulator. We have this emulator we selected. Okay, now I should press this. Run and wait. Okay, my app runs and my app runs. You can see this is our app. Avoid and the name my calculator. This is our app. Okay? Let's stop that and minimize this. Now, if I close this, I first want to see what's inside my main activity. Set Content View, What does it mean? It means set the activity content from a layout resource to show which layout is for this code, for my main activity from Resource. From Layout For. As you can see here, activity underlying main is my activity for this code. If I want to access this file, I just press Control. I'm on my keyboard and click. You can see the color is different, it's look like a link. Now click and now I have my XML that I saw in here. If I close it again, press control. You can do this too. Click I see the Target Activity. Long story short, when your activity class is open, press control, Click on the name and access the XML. Let's lose. And let I have just this layout and split so I can see the code and the view at the same time. At the default, we have this layer on our layout, this constraint layout that we have, this layer name constraint layout. Starts from here and ends in here. You can see if you want to end it, you just add this at the end. It's the same but this is extra you add if you want end this called closing type. When you add this, you can't close this. Layout layout in Android apps. Layout Manager are used to set the position of child views within the UI. You can effectively display your content using the right combination of layouts, we will teach you all of this. Android layout is used to define the UI that holds the UI controls or bridges that will appear on the app screen. All the elements in a layout are built using view and view group objects. Every application is a combination of view and view group. Every application view and view group A View is defined as the user interface which is used to create interactive UI components. Ed, image view, text view, radio button and all the other. Is responsible for event handling and generally called widgets. We call them most of the time, widgets. A view group act as a base class for layouts. Layouts, parameters, holes, other views, or view groups defines the layout properties, generally called layouts. Don't worry if you got confused. We teach them the best way we can during the course on the Android Studio types of Android layout, linear layout, relative layout, and all the others. Constraint layout is a view group. It used to specify the position of layout constraints for every choice. View relative to other view present. A constraint layout is similar to relative layout, more power, okay? Okay. Okay, let me show you what is constraint layout. Constraint layout can work as a parent layer to add your elements. For object in constraint layout, the position of each element is determined relative to the other elements. Let me explain this first object connected to top right left. Second object connected to top right, left. What happened if I move this first object just a little bit down? For example, I bring it down until here. What happened to this object will be as much as this object down. Why? Because these two objects are relative. This isn't relative to this, but this is relative to this. Do you understand what happened? Whatever happened to this? Go down or up. The second object will be follow the arrow connected to the parent or relative object. Whatever happened, they affect each other as the arrows. I make them do this. Okay. So what happened to this bottom one? If I move this one or this one, can you guess nothing? Why no arrows between them? This isn't relative to them. During the course, I explained it better on Andrew the studio. But I insist you focus on, on these arrows. How are they affected by each other? I explain this one more time quickly. This first object moves and the second object move down or up as well. Because this arrow and the bottom one not affected at all. Okay, let's continue. We need two box that take numbers for our calculator from the user added text. A user interface element for entering and modifying text. User can enter any value in this text box, but the type of text can be restricted using text. Edit, attributes, It attributes, you have all these attributes and many more. These are most important one. We cover these during the course many times. We can be sure you understand each of them and know how to use. Okay, let's add edit. What is edited is a simple that user can enter any text in it if I want to give the edit text, these two properties, as you can see, the edit text. First, think at these two because these two is the most important properties in edit text. I should press in here, I want to Andre tells me what options do I have, Control and space. It opens the options, I can choose between these, it's called intelligence. Anyway, I choose rap content. Most of the time you choose rap content or match parent. Some other times you choose other things. But most of the time these two are that we select match patent. The height or width of the object will be the same as the height or width of its patent. You can see how is the width in this example content, the height or width of the object. I mean any object, any object will be the same as its content. The more content, the more height or width, and why versa. You can see the width example. It is really simple. Okay? Wrap content, okay? Wrap content for this as well. At the end, this slash, because I want to close this edit text as I say. When I click, for example here and press Shift and this button, it shows me the options that I have. But if I click anywhere else and close that, if I click there again, I don't see that for that. As I say, I just should press control space. This helping window opens again and helps me to choose what do I want. For example, we add edit text. If I want to add a button just down with my keyboard, down button, inter add a button. Okay, I delete. Delete. Let's continue this in the next video. 11. Day 2: Create Layout - Part 2: Create layout part two. Let's continue. Don't forget a close your tag. You create edit text. You must close it, even you create this layout. You must close it like this. Lose. If you don't lose, you have error. You lose. It's not option. As I said to say, just press okay, this helping window comes up. What do I want? And text and wrote, let's say this text equals some value. Or the easier way. Let me delete this. Easier way is right. Android Studio helps you all which contains, I want this Android. I choose this one easily. And my value you see. Let me hide this and zoom. I can see what do I have? A little bigger. Okay. Now, if I change this to match parent, what do I have? Its it matches its parent. That is our layout. It takes all it. But let me change it to rock content. Again, rock content, just how much the content, I mean, this text needs for displaying. If I add some text at the end of it, for example, some of the you can see it's going bigger. And some numbers maybe you can see the changes. If I have the match parent, there's no difference. So I have this text or just the value, no difference is came from parents. I hope I can explain it. Well, let me see. What do we have if we change the height to match parent? Pause video and guess, then play the video and I'll show you. Okay, let me see if change this to match parent, the whole height belongs to this edit text from its parent. Be careful, if the parent only occupies half of the page, then the height of the edit text will only be up to the middle of the page. The weed and height come from the parent, since we have the layout all less cream, top down. So we have our parent sized parent. Okay, let's change it back. Rack content for our calculator. We need something like this. And just so you know, most of the objects has this wet and height, almost all of them. Let me say most of them. Okay, let's continue. But we have this red error, this underlying red under this edit text. And also we have this red error. It says you have an error, you should fix it. How can we fix it? What is this error? This error said you add your edit. Nice job. But. You don't specify where should we show this? What does it mean? It means you should say from at least one angle, it connected to something else. So the Android, when you run your app, can decide which side of your object connected to which side of what object can sort it out somehow. Let me show you. So you write to top of and you have the A layout constraint top to top of. I chose it and I said the top of my edit text should be connected to its parent. We can specify an ID if we have another object in here. But no, I want to say patent. What is parent? My constraint layout. My layout. Okay, if I do this, you can see this blue. My upper side of my edit text became blue. It's connected to upper side of its parent. As you can see, it's not Android, it's app. If I do this inside design in here, I just can click in this circle and move it a little left and leave it. The Andrew Studio, just write this layout constraint. Start to start of parent, We can type it in here, or we can do this here. In design mode I do. So you can understand what is the difference. Before I forget, you can see you have all the text in here. You have the attributes in here. See lay out what match parent, lay out Id wrap content. You have all other things, even text this value, If I say value, for example, this number at the end. And in there you can see this text changed to this I write in there and it added in here. Whichever is easier for you, you can do from there. I hope I'll explain it easy enough. We don't do with all of these things for now, but you know these are able attributes. Also, you have the attributes. These all attributes contain all attributes. You can see if I press in here, these all attributes will be open and all of them in here. But the usable thing, the attributes that we use the most, are these few attributes. Most of the time we use and work with these. But sometimes in the all attributes we have some other thing that we must work with them in the certain time. Okay, let me minimize. What do we have here? At the right, I have the circle. If I drag it in the right, you can see I have layout constraint to end of patent. Just so you can see, what does we call the bottom? I drag the bottom one to the bottom of patent. So you can see layout constraint bottom to bottom of patent. Because we connect up and down to the parent. Our edit text came to the middle. If I want to delete, for example this bottom one, I can remove it from here, Pt, the bottom one is gone. Since this is very useful, let me do some other thing with this that we learned so far. Let me connect it again. This time. Remove top this line. Remove it, it's go down. Let me reconnect it, it middle, let me see. Wrap content. The width of the edit text is limited by its text value. If the text becomes longer, the width increases and then again match patent. You can see it's really easy. You just should work with this. The more you work with this, the more you learn. Long story short, what does these four things do? You can see them inside attributes. In here, these things shows you where your object should be inside your view. L XML or your view, or your layer, whatever you want to call it in the Android device, should your app look like, how should your object be side by side? Because we work with these things a lot. I try to explain them as best as I can. Let's continue this in the next video. 12. Day 2: Create Layout - Part 3 (TextView): Create layout part three. Okay, we'll come back. We cover these and we don't need this one also. We remove this text because it's our first input in our calculator. Now I have three warning above. As you can see. One of them is autopi. Okay, let's autoph, go to Feel Hints. Feel hints for example there. Okay, What is this auto fill? It's for something that Android might fill it for you. For example, user name, e mail, or other things. It's not necessary for the calculator edit text, but we fill it anyway because I want to show you how reduce the warnings. Now let me look at this again. I need input type and accessible label. Now we have two ways in front of us. First, we can see the warning up here, for example, this label. Or we can go on this edit text. You can see this yellow underline. You can see this missing label for the hint, hint or label for one of those. You need one of those. Okay, first let me write this hint, this hint. Put your number here. No, your number here, it's better. Now it's hint. You guide the user that what should he do? He should enter the number here, of course. Enter your first number here. Let's run the app by pressing the button and okay, our app is now run on our virtual device. As you can see, it said to me, Enter your first number here. This is our hint. When you click on it and you type something, it gone. Why? Because it's just a hint. If I remove it, I still have my hint. But if I write anything, the hint is gone. My number or my text will be replaced by that. Okay, let's stop the app and of course minimize this. Okay, let's continue. Okay, so now you familiar with this hint. Let me add the label first I delete this, then I add the text view. Okay, text view Evi jet, which displays some text on the screen based on the layout, size, color, et cetera. You can write any text in this element. What is text view? This is text view. Anyway, attributes for this text view, we have some attributes like what is the usage? As you can see during the course, we cover these many times, as much as we can be sure you understand them well because it's the most important thing, you should understand them well. Okay, let's text view. This is text view. Okay, I have my text view. And of course rack content. Rack content. Now what else I need it? Text. Okay? I write first number, of course I need closing and I should connect this to top and the left of its parent. So I can either connect these circles to the top or the left, or just write the code inside this. I connect to the top and to the left Patent, Patent, and label. For? For label for what? Some ID. But my edit text doesn't have an ID, so let me add ID for my edit text. Instead of typing here, use attribute ID. For example, x. Now I have this xt value. Now I can give this exact to this labor form. Now, before I forget, I add text view. This text view is for showing any text, not editable text by the user. User cannot edit this text by clicking on it, but edit text is for input, this text view not for input. What do we have next? We have other warning input type. Okay, let's fix this as well. Input type. What is our input type in a calculator, of course, number, the user only can insert number. Now as you can see, we don't have that line yellow under line for the warnings because we fix them. Of course you have this warning because you must put it inside the value file and other things. We reach to them in the future lessons, but don't worry for them now, let's continue. Now, let me run this again. We have the and when I write numbers, I have this first number on the top, okay? Stop and minimize. As we can see, they were too close to each other, it's the problem, okay? I add this ID first input for my text view. I change edit text ID two EDT value. It's my mistake because it's edit text, I should start the name EDT. Since it's texts written law between programmers, I should write T first input now, instead of from the top, connect this to the patent. I want to change it. Control space, top to bottom of top to bottom off to bottom of kicks The first input as you can see on the view, this part connected to the bottom of this text view, so it's connected to the bottom of the text view. I have this error y because I write this thing extra idolated. Okay, let me see. I have another error. What does it here? I have touch target size to a small, it is to a small, it needs a little more height. Okay, let me fix that as well. Now I put mean height to 48 DP, so my edit text can't be a smaller, the height of my edit text can't be smaller than 48 DP. The result is user can easily touch it. If it's smaller than for ATP, it's hard for us, some users to touch it and select this edit anyway. As you can see, we fix this error as well. Okay, let me quickly run it again to see what happens. As we can see, I have this first number, I can write number. This is saying first number. This is our first number. Unlike our hint, it doesn't go anywhere When we write numbers and any other thing, If we write any other thing, it doesn't go anywhere. You can understand. Now what do we have this label for? We said this that we write what does it for? It's for this edit text. Because of that, we said it's label for this idea. What is this idea ID of the edit text? I hope I can explain it. Well, before I forget, you don't have to run it every time I run it a lot because I want to show you what happens. Okay, we don't have the second number. We can use this to put the objects on the screen, or I can show you other thing. Click here, the when you press the left click, you can use middle wheel of your mouse to screw it down like this. Okay. Now, release it. Press control C. Can you copy the text now? Control me what just happened. You create a copy of this text and this editas, but we have a small problem. What we have these IDs, we can't have duplicate ID in this view. We should change these IDs. What do I change this ID? I change it to 62nd input the text. I changed it to second number label. I changed it to T second value because I changed this edit text ID to edit second value. We already set mean height so we don't need to do it again because we copy it. And to the bottom of 62nd input to this as easy as that. Okay, look at the right side. You can see these are on top of each other. It's our problem. We have a problem in here. Let me zoom. And as you can see there on top of each other, what can we do? First, let me change this edit text value. I changed it to it first value, I changed it to it first value. Now I should change this label for first value as all of our IDs is good for now. Now let's change their position. How can I do that? I want this text view be at the bottom of this edit text. I change it to top of this text view connected to them. It fire bottom of this one. You can see this connecting to the bottom of this one. Okay? And this edit takes the second input, bottom of what do we have here now? This text view and then this edit, this text view and this edit text. Let's run it again. I run my app again. As you can see, I have my first number. This is my first number and my second number. This is my second number. Okay, Don. 13. Day 2: Basics of Material Design in Android: Material Design in Android. I run the app, but as you see, I still have two errors here. However, my apps can run how some errors are, just in the design part or XML files related to layout and can't prevent from running your app. It means they don't stop you. Instead of fixing these errors, I want to make my app more beautiful. Let's see how I want to do this, Okay? Material design, a comprehensive guide for visual motion and interaction design across platforms and devices, create beautiful and usable products. Using material components gives you more control over how your app looks to the user. Makes your application interface, user interface more beautiful and interactive. Saves your time. Many features that you need are already implemented to use material components in your. Be sure you have this line in your gradial file. Remember, version 1.11 0.0 may vary depending on the time you watch this video. What does that mean? It means version 1.11 0.0 is the minimum version that you use in the future you came to this point and this line, minimum version you use, is this. Why? Because you see this video in the future. And the version that I use at this time is this, your version is equal or higher minimum version is this. And of course, minimize, okay? Let me move it a little bit here. And zoom it with this hand right here, about, okay? So what should we add in here? Margin. Okay? A margin. How much margin? For example, ten DP. Ten DP, or copy this. Copy exactly this line to the other one. Okay, let's run this again. So my app now as you can see, I have this space around it. We can have more space. Let me show you. Okay, let's add a little more, for example, 30. 30 as well. Let me see what happened now. You can see my app now has more space between these two. This margin at space this, you can do another number, for example 20 or 40. It's optional I think to start, it's good margin or external space used to make a distance between objects in the page. To make your user interface more beautiful and user friendly, you can define margin for all sides and it lay out margin or each side separately. For example, if you want margin for two side and not the other two sides, you can define it for only two sides. Anyway, let's see the example for all sides with the same amount. Each of these four is for one side, For right, left, top and bottom. For example, you can only have four top and you don't, and then you don't have any margin for the other three sides. Okay. As we remove that text views, we should show something for helping us. We add hint, I add this hint. First number. First number. I copy this on the second number. Okay, I just copy this now. Change the text. Okay, second number now, as you can see on the right. First number. Second number. Okay. One more thing before I forget what is different between text and that hint. I changed this to text and I still have for the first number hint. Let me run and show you. Okay, as you can see it, write for me first number. And if I write 123, the hint will be gone when I remove it. The hint comes back. When I write something in second number, the text is still here because I write this text. If I remove, I can remove some of these, but I can't remove first number. If I type anything, the hint will be gone. But no, the text is the value of the added text. Okay, for now, I changed it to hint. Again, I change this to hint. Okay, let's run the app and if I type anything, our hint will be gone. What happened if I have more than two box like this? The more than two edit text, for example five it, ten edit. For example, for register I have name, last name, phone, e mail, and many other things. What happened if I want to keep the hints and also user can type text, text input layout, a material component wrap and edit text, or text input, edit text. It's better to use it with text input edit text. You can add style to it with a style attribute. Text input layout has some attributes, the most of them are these. For example, with hint, you can display hint as label some other useful text input layout attributes. For example, with lent, you limit the number of characters that user can in text input, edit text, a material component to get user input. It gives you more control over a style and how it should be shown to the user must be used inside a text input layer, different styles to show it in different ways. As you can see, it looked like this. If you change the style, you can make the look like this or any other thing. I'll just give you two examples. Text input text have some attributes. Some of the most important in those attributes are of course, ID supply as identifier to access the object later. Id is the name. What do we call this object? Almost in all objects we have this D many times it's optional. Most of the time we put an ID because we want to do something with that object. Anyway, input type, for example, the type of data being placed in a text number and the Oder, for example, if you give this input type number, you can only put number inside that. It means if your user try to put anything else, this text input, edit text doesn't accept and the user can only put number inside this text input it. T. Let me add. Okay, what should I add? Okay, Text, text, text. This one congule Android material, Textfield Text Input layer. Okay, I pressed in there, So I add this phone and I want to control space, say match patent, and this phone is rack content. Okay? Okay. Now let me close this. Okay. As you can see, we still have problem here because you can't close it like this. This, you should first close this part. Then Andrew, you close the other. For something like this, if you forgot, you have that error. As you see, I still have this problem error. Why? Because it doesn't know where should it be. Please explain to me where it should be positioned, where should it be placed or something like this. Where should it be? Because I want to place it, instead of my first edit text, I should copy the constraints from the first edit text. I have this position to here. Now we come down. I have this control x cut. Edit control X cut up, control, paste. Again, you have it in here, control V, you have this edit text inside this text input layout, see at the right is changed. Of course we should have an ID. What is our ID? It's input layout first, capital capital F. Okay, what Next you can see we have this red thing here. Because of this red thing here, we have error. Why? Because we say top of you should be bottom of this it first value. You might say we have this EDT first value here. But since it's inside this text input layout, this cannot recognize that this can only access to the outer layers, not inner ones. Input layout works as a layer, What is the solution? It can't find this, but it can find this input layout First, copy, control, paste. Now it's changed. Let me show you again Control. It doesn't know where it should be and it looks like this. As you can see, Control, look at the right control now. It, it should be under this. Okay? Until now, let me see what just happened, Okay? We have this different style, first number 123. Second number 123, don't happen. You can see one to three don't happen. But here it's more beautiful and we have the hint and minimize this. Minimize this and continue. I might pause, for example, minimize things you can see because I don't want to waste your time. Do we love this first number now? Yes, we do. What should we do? Go up, select this control C control easily. In here and slash, close it easily. Oh, input layout. First of course, change the ID. You can't have duplicated ID Second, because I want to place the second number below the first number. I should do this, copy it, and paste it in here. First number, second number. We have two added text. That is beautiful. Now let's run the app again. Now this is what I have. 123 and 123. And I have my, I don't like the color of second number. I want it to be changed. Background White. Okay, I have white. Okay, What's the difference? You can see what is the difference. Now let's make it more beautiful. Okay, remove this in here, we give it style. I added style style, base from base. Rigid material components, text impode layout. I have this, let me run. This is our app 123123. Like this, you can see the difference. Since we use this text input layout, we can use different, not just text. How we just tried input this for copy the side from here and paste it in. Takes, takes like this as you can see. Control. No suggestion. It should bring it for us. It's okay to copy this as well. And before I forgot, it shouldn't be. Text. It should be texting, put, edit, text. Since Andrew Studio doesn't bring it for us, I just type it myself. Okay, Let me run this. Okay. What do I have? First number like this? Second number like this. Oh, my text is like this. What should I do? I think I give it too much margin. For example, if I give it 60 only and we said, now it's better. But you can see the thing is design thing. You can learn these things. What should I do I do to make it better? And other things during your learning, you can understand these things happened. What should I do to make it right anyway? Let me copy all of the thing down here to there. For example, I changed my edit text. This change as well. The we have it here as well. I think 60 and sorry, I give mean height six. I should give it six. Okay. And these are unnecessary. And this copy and ha in here, okay? They're both are the same now. And minimize something like this, it's better. I try to show you more ways to do one thing. So you can choose between them. What do you like do in that way? I'll show you many things. Let me show you counter as well. I have this input text and I have this layout. I add here counter as it should be true. What is this? Let me run up again, 1234. You can see we have this. What is this? We have four number. If I say 111, I have three, one and something else. It's better to use Max as well. Max Len counter. How many numbers? Maybe because in the future you can see you have limitation in the numbers. For example, can't have 500 number plus 500 digit number, you must have some limitation. Maybe ten, maybe 15, maybe 20 numbers, but you can't have infinite numbers. You should limit how does it work? First, let me copy this. Control C in here. Control, as I said, you see Edit Control, Copy and Paste Control. I do this from my keyboard, okay. Run. Minimize ten number, 1, 2, 3, 4, 5, 6, 7, 8, 9, and 1 0, it's ten number. If I write two more one, you can see it became red because maximum is ten. Okay. Before I forget, I should mention you can see these things we added, for example, counter, counter enable and other things, maybe even style. You don't have these things on simple edit text, you have them inside these more advanced added text. 14. Day 2: Quiz: Okay, welcome to day two. Quiz question. Question one. What is launch activity in an Android application? I repeat, what is launch activity in an Android application? Question number two, how objects in UI are positioned? Constraint layout. I repeat, objects in UI are position using constraint layout. Pay attention. You can pause video and answer that or write your answer in a piece of paper. Anything you like any way. Question number three. What is the difference between match, patent, and wrap content value for Android layout with property? I repeat. What is the difference between match parent and wrap content value for Android layout with property? 15. Day 3: Day 2: Quiz Answered: Okay, to quiz. Let's answer our questions. Question number one, what is launch activity in an Android application? The very first activity that runs when you open your app in an Android device. You can assume it as the default page in your Question number two, how objects in UI are positioned using constraint layout. In constraint layout, the position of each element is determined relative to the other elements in the page. What is the difference between match parent and wrap content value for Android layout with property match parent, the width of the object will be the same as the w of its parent. Do you remember from the course, it fits the parent wrap content. The width of the object will be the same as its content. The more content, the more, the more width, and vice versa. As you remember, we also see this on the course. I hope you answer them all correct. If not, you can always review the course. There are many more things you can learn on the course. 16. Day 3: Add Buttons (Button Types and MaterialButton): Okay, at what? Okay, welcome back. I just zipped out my previous day doors and I'll put it inside the lessons so you can use it. Okay, let's continue working in Android Studio. Use the icon next to the code blocks to close the code blocks, or click on the icon to open the block. What does that mean? It means click on these to close the block and click on the to open Del. If you click on, you have something like this. And if you click on these, you have something like this opened. Can you see? We press and press I can also press the, Can you see what's happening? Press we minimize them. It's really better, even the comments. We minimize the comments as if we select these or these. You can see them on the right, but we minimize them. So we can easily go between them. Remove extra. So it's all our code comment, this comment and this, and nothing else. It's better, especially when you have lots of objects in your layout. It's really, really better. Okay, now it's really organized. Now, what my calculator? Okay, now I added two text field to get user inputs for my calculate. Now it's time to add buttons to calculate different arithmetic operations. We would like to have something like this at the end. But what is buttons? Buttons communicate actions that user can take. You can use buttons in different places in your app user interface. Or for example, for cards, dialogues, model Windows, tool boards or all the other button types. We have four button types. We have text, button, outline button, tiger contain button. What does that mean? How should I know which one is which? I give you some examples. You can see this, it's text button, You can see this Outline button. Outline button looks like this. Talbot looks like this. Tgalbtens can be used to sell from a group of choices. We have 123 choices, we want to choose two for that. We Galton user can choose any of and Contain button most of the time we use contain button at the moment in our app we use contain button In the future use other buttons as well, other type of buttons as well. But for now I just want you to know we have these four type of buttons, so don't be confused if in the future we saw these, you say, didn't you say, we have only this type of button? No, we have other buttons for now and later on, the remaining three. Okay, let's continue. Material, A button material, as we said. Contain button, That is what we work with. This material button has some attributes. Some of the most important ones are these. As usual you have the ID. What is ID? The simplest way, as I said, ID is equals to the name person you call his or her name. It's his or her ID. The ID is how you identify a team. Any button, this material button has an ID. Other objects as I said in Andrew Studio has IDs, any shows what button we that shows on the button. We have some text on the button for example pelos minus or other things that can find on the attribute. Of course we have other Add button, we can add button, but for now we don't add button. We add Material button for that. Okay, if I right, I have this Button Material. But as you can see, okay, I have this Google Android Material Material. But this one I add more advanced button. Okay, I added and wrap content. Wrap content. And we, and this height, and we close it like this, I have this error. Why? Because we're inside constraint layout. What is the rule for constraint layout? You should always specify where is your object connect to connect to left connect to where. We should specify that. We should say for example, upper side of this button should be to the down of this. You see this? Let me do this again. For now, it's parent because it's connected to, but I don't want that. I want it be connected to bottom of the second number. I have this layout constraint top to bottom of input layout second. I do this without writing. I just want to show you you can do in this way as well. I still have this problem. Why? Because I remember at two direction, so one direction is left, at least two directions. So I want to do this without writing any code as well. Just come here, click, move it left, and release Layout Constraint Start to start off what parent? Okay, I solved the error. I solved the problem for this constraint layout. Okay, let's add another button. Material button. Of course we just copy taste. We have two button on top of each other, but I want the second button to the right of the first button, so they are not top of each other. What should I do? You should add an ID first for the first button. Okay? Id, Okay, BT N, so layout constraint. Start to the start of parent. No, we shouldn't say even start of. We should say two to what? Yes, to end to end of who? To end of N. Look at the right. In the peer review, the button is moving. This time it's to the right of first button. So let's do this again. Copy. Okay, I have 123 and four button. Three of them as you can see are on top of each other. I should add the ID and do the same thing, but I think there should be a better way. What do you think we continue the better way in the next video. 17. Day 3: Basics of Linear Layout in Android: Linear layout. Okay, Let's arrange them with the better way. What should we do? We should a L linear layout. Types of Android layout. We already talk about constraint layout. We have many different layouts. Now it's time for linear layout. Linear layout is a group, is a view group that aligns all children in a single direction, vertically or horizontally. It's a very useful layout since that we want to talk about it in this session. Okay, linear layout attributes. We have these five more useful attributes. You have other attributes as well, but we work with these five very much of course. Id, supply and identifier, you can call your object with this ID. It's look like a name for a person orientation. You can say things should be vertically or horizontally. Height. And of course, Gravity. We cover gravity in the video as well in there. Okay, Of course. Content Content. I just press inter, inter, inter. Nothing else if you like to know. I mean three in in and another in and another in. Of course, we can add constraint layout. In this constraint layout, I mean any layout inside the other layout. But I think it's better for this course and this situation to use linear layout. Okay, let me close this, since I write this one, Android Studio, write this for me now. I can put anything I want between the start and end type. Like usual, we have error. What is this error? It said you should specify where should I show it? Why it's simple? Because it's inside constraint layout. Constraint layout rules said you have to specify every object inside me inside this constraint layout. Where should I show them? At least you should specify to anchor for it, you see for example in the material, but specify two places to connect, one for a start, one for top, at least two. If you put one, even one, you have the error at two. Anyway, we have this error as well. Let me solve it. How many ways do I have one? Use this view with mouse click and drag to the place that I want. One way is this second way. Come here, press Inter and start typing the code that I want. Like this, a layout constraint, start to start to the bottom. Of all other things, this is the second way, just type. But my favorite. My favorite. And as I can suggest it is your favorite in the future. Come here. Oh, I love it. Control C. Control. I really do love it. We try to make it the best Android Studio and Catlin course as possible. I try to tell you the most tips and tricks as I can, for example. Okay, input layout second. There is Input layout, This is Input layout second. But where is it? How can we find it? On the left bottom of your keyboard, you have control key. Press that control key and then move your mouse on this. If you click on it, you can see what does point to, what does it pointed to. Click it means, let me try this again. This is my linear layout. It top is to bottom of input layout second, but I don't know where is the input layout. Second, how should I know? Press control, go and click. It shows you your ID came from here. As easy as you see. Okay, what should I do next? I still have the error. Let me add another one. Copy and paste. Because I don't have the third one. I just add. I should add another one or I can do something else. Let me see. Instead of telling this my left should be connected to the parent left, I can easily remove the Look exactly and change my weight match parent since the weight is from the left to the right and feel entire possible with our left and right position solved. We don't have any problem for where should it be. Into the middle, into the right, into the left. You add to solve this problem, where should it be? But since I add this match parent, the problem is solved. It is from left all way to the right. And there is no other space, so I don't have to specify my left and right. I still can, but I don't have to. My error for this constraint layout is gone. Now I hope I can make my point. So we have this linear layout. Okay. Other inter, what should we do with this? We can select this and this and control X cut control. Paste all four buttons now are inside this linear layout. Since they are in my linear layout, I don't have this. Why? Because linear layout doesn't need them. Delete the others will be deleted as well. Okay, I delete all of them. You can see on the right, I delete them, but there's no difference Why, Because it's linear layout. You can see if I click on linear layout, it's said this is my linear layer. It's a line. And the top to the bottom of the left, right and bottom not connected to anything. And all four objects are inside of this and arrange like a line. What do I mean when I say this is like a line? You see if I say orientation, I have this orientation that is horizontal. By default, if I change it to vertical, you can see all the buttons are vertically to each other. Placed to each other vertically. But by default, they are horizontally. If I delete this. It, consider it as horizontal. If I control space, right? The horizontal, they are horizontal. If I remove it, let me show you the default control X. Still the default horizontal. One more time, this is vertical. I hope I can show you how does orientation on the linear layout works? As you saw in linear layout, we can't put two objects on top of each other. Why? Because they are side by side in a line. But as you saw in constraint layout, we can put them on each other as we do this many times. Let me show you better constraint top to button control X. Now you can see the buttons and this linear layout are top of the other objects on this constraint layout. But even at this time, all four buttons are next to each other and none of them are on top of the other one. Why? Because this is linear layout. Remember, please remember, you should know how linear layout works. You should know how constraint layout works. And based on your need, you can decide which one is better on the different situation, of course. Okay, I have the A. Let me add the other IDs as well. Okay, I already added PT and I added now PT and minus. I added as well PTN division. I just remember I should show you something else. You see if you click here, not just click, it's click and not selected. So I just click Press control C. On my keyboard, you can see the Android Studio copy the whole line. As I say, the most important in this course is to show you as much as I can, tips, tricks, and things. Why? Because I have many years of experience. What does it if I can't tell all of this to you? Okay. You can see I just click and press control. See the whole line copied. I click here, just here. Do nothing, not select, not anything. Not press Inter on my keyboard. So I just press control. We the Android Studio, add another line and do the inhering for me. Add this thing I just copied as easily as you can see and add it for me in new line. But I have error. What is error? This is duplicated, but it's no problem. Let me okay, PTN multiply. I add this PTN because it's a custom rule between programmers. It's not have to, but it's better to do so. I have this vertical and let me change it to this horizontal as well. It's optional, as I say, it's the default horizontal. Okay? Okay, I have one more problem and another tick. For that I want to show you they are stick to each other and this one has extra inter. This one is bottom of the thing and it's not good. What should I do? Maybe see inter. I have many in and many other problems. Even here, extra space, unnecessary space, and bad writing code. What should I do, especially when my code is really big? For example, you can see I have only 116 lines. What if I have 500 lines? How should I arrange them? I can use menu code in here. Format file control plus plus shift plus L. You can press on your keyboard control Shift plus L or came to the menu code and press Reformat file. Now Android Studio show you this, you want to reform file activity under LinemmL. What do you want to do? I say I want to arrange code. Do not keep line brakes. I want to do both of these things. Run. Do you want to remove custom line breaks? Yes, I do. I don't check this because sometimes maybe I press no. Okay. Yes. Now, what do I have? I have the spray bring all of them but keep this one because I add these inter myself. But you can see, for example, if I don't have the and they are now stick to each other, you can see they are sticking to each other control shift and L, it said, you want to do this I said yes, yes. It added these Ers and arrange my code. I can now read my code really better. It's a very useful command. I do this many times in different projects, even in my code, I can use that to rearrange my coat. I think you should know all of these things. Okay, we should add some text for each of these buttons, but we keep it for next video. 18. Day 3: Working with Texts and Strings (How to manage Stings values in Android): Text and strings in Android, okay? This one, as you can see, our object has ID. And it's something regular, something steady, something common among other objects as well. Whenever you see an ID, it means you give this object a name like this, you have this text, okay? All the objects that can show a text on them have the text attribute. It's works similar to the other objects. You give it a t and it shows you that text in your app, for example, we have this property in the text input layouts as well. And the other, let me give it a value p, I give this plus, you can see this plus in here. Okay, I just copy this control. Why didn't I just press in here and press control? Because I have extra characters at the end. If I copy, I might have to remove this. Okay, Paste. But this shouldn't be plus. I should put this minus as well. Instead of plus, I should give it division as well. I should give it multiply, this four multiply. Look at the right. You have these four buttons. Let me run the app. Okay, I launched my app. You can see plus, minus, division, and multiply look like this. But wait a second. I have this yellow line in here and in here. Here, here. Second number, even here. Why I have all of those yellow lines? What should I do? Let me go on that. It said, hard coded string star should use a sign string resource. What does that mean? It is saying you should put all of your strings inside resources. As we can see, the full resources. I press Projects, so I can see the resources, the full named values, open values. Okay, I open it, you have the string. You should put all of your strings inside here. Also, you can ignore it. It's okay, your app is running. Now you can see I run the app. It's okay. But it's recommended you put all of your strings in here. It is very useful, especially when you want to use second language. Just imagine you publish your app and now you have many users. Now you want to use second language, Third language, maybe ten language. What should you do? This string helps you in those situations. This string foil helping. It's great. It is better and recommended. You put all of your strings in here. Where to say strings, it's recommended to put all your strings in. String foil in and studio advantage. Easy to manage and mudiqly your text and strings. Easy to add other languages for your app. I mean localized string values. Disadvantage. None. You can see where are strings? You have strings foer under this fo you have stringr after this thing. You can see the language Exml structure. String values are restored as a pair of name value inside the string like this. You can see like this name, this is the name to indicate which thing you mean to show in an object or other things. Value mean to set or modify what should be shown on the object. Remember the value is what you show to your user example. It's better. Okay. And Roy takes, oh, it's good, equals string, this reference to that string file we talk about inside that file. This inside that file, you look for the name T R, you look for this name inside this string name, you had TR ad this name for the text you showed this value. And if you change the pelos character to, for example, this text add, now you have the exact same thing. But when you run your app instead of this pelos, you can see this app if you use it in many times and many places, just you should edit this one and all of those places are replaced. Okay, We change it to this, we talk about this name. We change from these to this, This is at this. Plus if you can see, I place it in here and we change it to this. Everywhere that we use this name like this. Now change, I hope I can explain it. We cover it in the video, we can be sure you understand it. What's inside this, it is resources, start and resources, a string name, app name, my calculator, your string name. Each of your strings has a name and each of them has a value. For example, you have a string that called a name. This is your app name. The value is my calculator. How can we add this? I can click here and press Control. Copy and control. Other control why? My first control doesn't work because it is already selected this line and the text that is, just copy it into this line. No difference but second control. Add this another control control and I can change each of these names and their values so I can use these names inside my app. Is there a different way? Yes. If I want I can duplicate. Let me show you that quickly as film. It control D here. Duplicate line. It doesn't copy your code and then you want to paste it. It just duplicate that line anyway. Control, control, control, control easily and controls it to undo what just I did. Either way. Let me quickly back to here. You can see if I go in there, I have this lamp. What does this say? Extract a string resource. If I press this, it says, what does your resource name? And of course, you can see the value, but what should you call it? Let me see what should I call it. Okay, T R underscore ply. Okay. I personally recommend this you add everywhere this SDR between before your string name. It's easier to understand. I press, okay, and as you can see, a sign, a string STR multiply inside our string file. Look inside our string file, go and find STR, multiply, whatever that is. Put it here, let me see. Str multiply the Android Studio just added for me, what is the value S star? Anytime I want to use this, I can easily use it many other places. If sometime I want to replace it with the text, for example, we multiply instead of this star. I write just in one place. All places that I use replace, you shouldn't have many language. Even if you have just one language, you can use this many times, many places. If you want to change it or correct it, you can easily do this in here, Do it in here. We came to this string, XML. But what if I close? I don't know, where is this axe string? I can show you. It's here. But don't, where is it? I'll show you the tick. Let me refresh your memory. You press the button left down on your keyboard. The control button, press it. Move your mouth. If you click on it, it shows you Where does it come from? Pre. It came from here. Even exactly, show you what line you see. Lose it. Press exactly from here. It is really good. Okay, let me do another. I have this, but I want to do this with hint. Okay, I have the hint in this text input. Okay, I have this. You can click or press Alt plus In. What does it mean? Press Alt and it opens this for you. Or you can press in here or a in. It's the same. Extract string resource. Okay. Our resource name will be first number and the value, the exact text that we write. Okay? I just add STR underscore, okay? And the yellow line. And if I press control and click on it, this is our STR first number and the value is first number. Is it any difference? If I run the app, do I have my first number takes? Yes. You still have your first number takes? No difference. You just organize all of your takes. Okay. One more. I use the lamp or a inter, okay, to show you the boat. C, R score. Okay? Done. I don't press control and click, but as you can see, no difference. All of them are here. Three to go. I'm not doing these three. And keep them for next video because I want to show you what is multi language like in the next video. I cover that as well just to be more familiar with that. We are not going to create a multi language because we are just beginner, but we do this in the future. I just want to show you how does that work. Join me in the next video. Thank you. 19. Day 3: Introduction to multi-language Android apps and localization: Add strings for another language. Okay, they come back. We have this Android view on the top. You can see it. Android view Android. We change it to what to project. This is how your project looks like on your hard drive where it's saved, okay? I open the app, I open the SRC, means Source, open main, this main folder, okay? I open RES resources just a little bit more, okay? I have this folder values. I open it as well. Color string team, you can guess color is for my colors. And this string has all of my strings. So we have the resources how to add another string that M change Android View to Project View. In project window, you can see this step two fine. R E S Foll under app SRC Fol. In this on the app SRC full, find this all your resources, RS resource. The right click on the resources and chose directory, this resources right click new directory, Step four, name. The new directory name should start with values. Continue this character with your target language, but not the whole. For example, if you want French, just if you want to use Arabic, R, it's really simple. Step five, copy the current string XML file into the values directory, to the new directory. What you have, the values, these strings inside it. You copy that inside the values French. As you can see, for example, I already have Arabic. You can have many language, as many as you want. Anyway, step six, back to the Android view in project window. I mean this. Step seven, now you have another language strings that can be easily translated and modified. As you can see, you have String, this is default. You have also Arabic and French. You can see this has nothing after this default language fixes in strings Em, I'll give you for example, English, E, N, French, F, R, Japanese, J A, and Germany G, E. Right click here. And the resources, you see resources S, right click. New directory now values. But I have values. Yes I have values. This is my values, it's my default values. My default values are English. Now what I want another language, let me see. For example, they have right to language opposite direction. It's good. A, R, Arabic, And press Inter. I have these values, Arabic, R, what. Now, right click and copy or control. C can here and paste. What should we paste? What do we have in here? This string? It's just like our previous string. Why? Because we copy paste now what changes project to Android. Now you have all these default string you, Arabic strings. You can see Arabic. And you can see the two after the folder name, because you have two strings. Okay, let me translate this Arabic. I just copy these. And I take it to Google Translate because I don't know any Arabic. I paste it there and just copy Result and bring it back. Wait, okay. Translated. Paste. Okay, my calculator. And that is Star. But these two, these are translated. Okay. As you can see, since I copy and paste from Google Translate, one of my names cropped it, what should I do? I go back to my original, I can see the copy and bring it back in here. Our second number. Okay. If you have all of these problems, it's better you just copy this and this text and 1.1 take them to Google Translate and bring them back. If you work in a company with many other persons, it's better to give it to a person who works as a translator, not just use Google Translate. I just use Google Translate to show you how does it look like it's not professional. If you want to do it professionally, a translator should do it for you person. I mean, anyway, it said it translations for all locals in the translations editor this pattern. Let me try it. Click what do I have, these four keys resourceful on translatable and default value. What does this mean? My default value. Do you remember? I said I have a fuller with my default and I add R. My default value is the first number, my default value is the second number. But my translated text is this and this. If I have third language, for example, French, I have one other column for French, Chinese, Japanese, Korean, or many other languages have all the other columns. I hope I can show you. What do I mean? Anyway, the just to be sure, we have this second number here and this second number here. The name should be the same, only the value should translate, the name should be the same. Even if translator crafted, you should bring the name back. All the names are the same. Let me show one more thing in this editor, this column table, what does it mean? I have this star for multiply, but the star can't be translated. I just have one star in all the languages, for example, I just check this. My star just have the default value. Let me show you other thing in other ways, check this. See, I have this start in here in Arabic and I have this in here in English. If I remove this from here, for example, like this, I don't have it anymore. I use control if I want. Can I bring it back anyway? I don't have it. What happens now? If I came back to the values by defined value, I have this red line because I don't have a translated name in there, so I have this red line. But if, let me close it and open it again. Okay, this is star, I have this red thing. And it said, we don't have it in Arabic. Said key K, R multiply has translation missing for local Arabic. But if I tell it it's translated, it doesn't have any translation. It's just a star in all the languages. Or maybe plus division minus. Anyway, it isn't read anymore. If I come back here, it isn't read anymore. Why? Because translatable equals false. It can't be translated anymore. I hope I can explain it well. Okay, now what? Now I have this and I want to add this plus as well. What change you see. Resource name, Resource value, course K, ST. I have this as well. Values Arabic. Okay, So I check it. I have checked in values my Default and my Arabic version. I press this, okay, And string CR. If I leave the mouse here, you can see default and Arabic value as well. And I press control left down on my keyboard. I move the mouse on here. Multiple implementation. Oh, what is multiple implementation? If I click it, said I can't take you to there. Why? Because it doesn't have single place. It has multiple implementation. You can choose your destination. You have one in the values and you have one in this Arabic. Which one do you want? I say show me in values, it shows in values. Let me try this again. Control. Click now. Show me the Arabic version. I have this in Arabic version as well. If I leave the mouse on the name, in here, I can see the configuration in Default and Arabic, and each of the values for them. Just to be clear, we do this to show you how can you have two language, you have many other languages, even ten languages. And as you can see, it's really easy. It's really simple to add other languages, but it's good for now and very useful instruction for how can I use strings. And because we are in the basic level, we can't add language in our app for now. But just for you to be familiar with these, we cover these things. Okay? Just add the other, for example, the alt inter, STR minus and Arabica, I also add this STR D in the stream, you can see a minus. I have it. And even multiply. As you can see, I don't have that yellow lines in here, because it is now on the way that Studio and Google recommended. Imagine that you have. Use this at 100 place or this first number in 100 place? And you think, what should I do if I want to change my, take this string first number? You can see I have the default value in here and this is my SCR first number. I think I should add an S at the end of this, for example, this first numbers. Or I want to change it to something like this, 123 and second number 123. And three dots and three dots as well. What happens now? Anyway, it said for three dots you can have this character, but I just use two dots because I don't want to go inside that A. Anyway, I just continue to lessons, we might reach them in another lessons. So first numbers 123 and three dots. Second number 1232 dots and these characters. So imagine I use it in ten plays, 15 plays, 100 play. Should I go change every one of them? Of course not. If I add this or any other thing after that, all places that I use change. Now you can see first numbers 123. Even if I run my app, you can see inside the app, they all are changed. I use it in 100 different places, All of them change all at once. Because I change them in one place. Even if I want to change this plus two, what happens now? Come back, you see this ad. If I have two language in my app, I can write the Arabic word for the ad in that language. If my app changes the language to Arabic, the user can see this ad in Arabic language or any other language. Okay, let's change it back. A long story short, even if you have one language, it's better. It's more better to use the string XML file. You can organize your text. We continue with our buttons in next video. 20. Day 3: Buttons Properties : Properties four buttons. Now, we have these four buttons and we would like to make them better. What should we do? We have this linear layout. Okay. Press. We have gravity, gravity versus layout gravity. Gravity arranges the content inside the view means for object. Layout gravity arranges the object views position outside of itself means regards to its patent. Let's see the difference of some of values in this picture. Also, there are other values as well. But just see the difference here. The blue boxes are text field inside a linear layout. Let me see. With gravity, we have center left Android. With layout gravity, we have center left android, by its patent, not by itself. Notes for gravity versus layout gravity, gravity, wrap content and gravity are meaningless together. Gravity doesn't work well on a relative layout, but can be useful with a linear layout. Layout gravity. Layout gravity only works in linear layout and frame layout. Match parent and layout gravity are meaningless together. Everything with layout under line defines something that affects the elements outside. Please be careful. Everything layout underline defines something that affects the elements outside. I think we should make it more bigger and bolder. It can be center and all the button or center now. So we learn how to use gravity. Where can we use gravity. Can we use it in other places? Let me try. Control C. I copy all the line. I have the second value, and I press Control and gravity center. What happened to second value? The second number now center. Let's continue. I have this as well, Control. And I have this in center. What else do we have? I can write instead of center I have my first number at the end. You can see the hint at the end, or even start, I can have it at the start. It's the different value as you can see. Anyway, let's continue to this linear layout. I have this in match patent. What if I give it rap content. I give the gravity to it and I said B at the center. But if I say rap content, it is center, but it doesn't have any more space. You know, linear layout now is wrap content. So it's the size of its content and the content is center. But at the left and the right, there's no more space for it to be anywhere else. But if you say match pattern. Now you have the space left and right. Now if you want to be center, you have the space to move or if you want to say n you have the space to go to the end, but wrap content, there's no difference between start or the center when you wrap content. Why? Because no space is here. Anyway, And the center. Long story short gravity is for the inside. For example, you can see the hint. The team that inside changed its location, not outside. And in the linear layout, the teams that are inside the linear layout are changed their position, not something outside. The whole linear layout doesn't, doesn't move. But the things inside linear layout move with gravity. So we can understand how the gravity affects our objects, our all object and get on our screen. I have one more object to show you. I have this BTN ad, for example, inter G since they are already centered, I put start. So you can see the plus at the start now. Let me delete this. Anyway. Okay. Let's layout wait. You weight 0.25 one quarter, it's from one. If you write just a five instead of this, half, it's deviated to one, how you infer your two digit number, it equals percent it's percent. It's 25%, 25% to this, 25% to this, and 25% to this and 25% to this. Now, all four buttons have 25% for them. Let's make it more beautiful. What should we do? We add margin. Okay. Okay, eight D P is good. If we say one D P, something like this, if we say 20 DP, something like this, eight is good something like this. Nine. It's good, but how about if our project became bigger and we have more margins and other dimensions. What should we do then? Like string, as you can remember, we have this string here. These we also talk about other languages as well. We have for dimensions. And we should put these numbers and values in there. In value cli li, new value resources file. Okay. Diamonds is good and say. Okay. Okay. In this file, I need to have a de men name what should we call it. Ten margin and let's close it and say or let's say nine DP as we write now let's use it. We have the nine here. Control space, we have button margin. You can see at sign diamond button margin has the same value. I put my mouse on it nine DP. If I change it to 11, you can see I have 11 DP. For any other value. Now I have. Because we define this, you can also use it in here for text input. But I name it I name but margin. Let me change the name. Let's call it normal margin now. Change it to normal margin and copy this. I have this layout margin. I want this be normal margin as well. Since I didn't put the same type for my first text, I just use it in here. Let's have this margin for other buttons as well. Control C. Now, Control and control, sorry, Control and control. Just like this, it's beautiful. Okay. You can use this margin with other things. You just press control C and copy this for this text input field, you also have margin. Property margin or comments like ID. Many of these objects has margin. As you can see, there's the difference. Control, paste it again. Look at the right This is the difference. Let me give the upper one not this one. This already has the margin. I want to give it to this. For example, control, I give one to this. I press control and paste it again. Look at the difference control this change because the margin. How does it have seven D P? And as I say, if I change the seven DP in here, all places that are used are changed at the same time. Okay. And I only change it in one place. Okay. We can run the app and see what does it look like, but you can't do it yourself. And an extra tip. I just run the app for myself to see what happens. It gives me an error. And I choosing this APA tty one. I change it to this API ty four and it seems to fix the error and I don't have any problem. I can run as you can see. So before you get worried and do anything else, check these basic things. For example, your API level or the other things, or maybe we rebuilt, you can fix the problem. Anyway, see you in the next video. Okay. 21. Day 3: Quiz: D three quiz questions. Question one, what are the different types of buttons? What are the different types of buttons? Question two. What are the usages of attribute Android ID. What are the usages of attribute Android ID? You can pause the video and answer the question. Then resume the video and continue to watch. Okay. Question three. What does Android orientation attribute do in linear layout, sorry. What does Android orientation attribute do in linear layout? Okay. Question four. What is the difference between gravity and layout gravity? What is the difference between Gravity and layout gravity. Okay. 22. Day 4: Day3 Quiz Answered: Day three quiz. Answers. Let's see what do we do. What are the different types of buttons? We have text button. We have outline button. Tugalt and contain button. We have these four kind of buttons. Question two. What are the usages of attribute Android ID. It is an identifier and is used to access an object later. For example, to define another object position related to that object or in the code to change or modify the object. You can pause the video and read the answers by yourself and compare them with your own answer? Question three? What does Android orientation attribute do in linear layout? It defines the direction of the objects inside a linear layout. Horizontal for a row vertical for a column. The default is horizontal. Question number four. What is the difference between gravity and layout gravity? Gravity, set the content inside the object. Layout gravity, set the objects position outside of itself in regard to its patent. 23. Day 4: Result Section: Results section. We need a result part for the result of our calculator. Let's close all of this. I lose all of this. Now I have this after linear layout. After this linear layout, I want text control space. I have wrap content selected. I just press in and in control space, in. We still have this red thing because we should say where this thing we want to be. Where should it be shown. To bottom of layout contrate to bottom to bottom of patent. I just press inter when I selected and I write start and start to start off and pent I have no error, but it said you must close. I write slash and and you add this no error. We need a text as well. Let's write text and the text is common between the teams that are visible and can take text. I can show you the text. We have warning because it's better be inside as you remember, strings. Press and press inter at the same time to see what should we do? We can click on the light ball. You can see click or press in Extract string resource. We have let's put it at Arabic as well and resource name. We add ST before this name. You remember Arabic we added press this Ken you have aTR result in here. We have this Arabic in here. What do we have until now, we close this I use this hand. We have this in here. If you want to see it better, you should unselected. You can see it's selected now. We click anywhere else. You unselected and you can see result in here. We have this. Let's Let's write more margin. And inter and control space, we give it normal margin. The margin is for some spaces, a little space from the edges. Now, it looks great. Let's continue in the next video. 24. Day 4: Result Section Part 2: Result section part two. I need a line. I add layout width, as you can see, it's required. I give it match parent, and of course, height. As you can see, it's also required. I give it two D P I write an Slash to close this up. As you can see, we have this line now in here, but I don't want it there. I want it in top of my result. So first, we give this text the D. T X t result label. As you can see, we have this red line under the view. It said, you should specify where you want to see this view unless we show it on the top. I say, Okay, I'll specify where you sh show this to me. Bottom to top of top of t x result. We just give the ID T x result that we just give the ID. What just happened? We have this down here now, as you can see, We also should give it background. So we write back ground, background, what color? I think the like is good. The like. And now we have this line. No more. So you can see As I want you to see, I give it, for example, 12 DP. You see this is black lie. Okay I'll give it I'll change it back to two to two DP. Since we don't have a line in and with the studio. We create view and we give this height and w and we give this view background. For example, the lag because we want the lack line, and whatever height we give it, we have line with that thickness. You see, I just change it to 11 12 DP and you can see thicker line as easy as that. If I give this wit, for example, five DP and give this match patent. You have line like this, two DP again and match patent. I'll change it back. Let's have some padding for this text view, press in there and in here. You can say Android and then say padding or just say padding. We have this normal margin as you can see, but I think I should specify something else for the padding. No. I open values. Let's see. We should create something in here. Control C in this line and press press inter Control V. I said you can't have duplicated. I say, Okay, let me just have padding. I have normal padding and I want to have a little different between this, I give it eight. Let's close this. And for the padding, I'll give Normal not merging, normal padding. Now we minimize this like this. As you can see, padding is for the inside. If you don't have this padding, let me zoom it more. I'll cut it. You don't have this internal space. Padding is for this inside, internal. Let me show you bet. For this part for the internal side, you have this padding. If you don't have it, you don't have those space. And if you don't have this margin, margin for this outside. It's look like this. If you don't have padding, padding is for the inside, if you don't have margin margin for the outside. If you change the values for the padding inside spaces became less and or more, and for the margin, outside space became less and more. Less or more. What else do we have? For example, we have this padding, and also we can specify this padding for top or bottom. Bottom, I think it's better sample. We have this for the bottom. For the bottom, we have this like this, remove bottom padding, like this, back button padding, like this, and only have the padding, it's look like this. What else do we have? Bottom start top and many other things. But most of the time, we use the padding. We use the margin, not specification for the bottom or the top. And But but you can have those things. And I think we reach them in the future courses as I plant. I'll give you one more example. You see this margin. Let's change this margin like padding for not bottom not to for a start. You have the margin only for a start, only on the left side. And if you remove this, you have it all around. Enough of this, let's copy this control C and case in here. You said you have duplicated names. I remove this label. It's okay now to start off no end to end of what to end of this result label. Why do I do that? Because I want this to say the result will be here. And I want this one to show the actual result. So this one for knowing where is the result and this one to showing the result. Let's connect the right side of this to here like this. Let me change the wit. We have wrap content, but I don't want this much little. Let me have match parent. But we have one problem as we can see. It's on the other text view. If I change it again to wrap content, as you can see, it's too small. So neither of them helped me, and I want this from here end of this text to here. But what should I do? We can write zero DP like this zero dP. What just happened. It's not too big. It's not too small. It's just the way I want this zero DP for the w. When you can use it, you can use it when your left and right connected. If for example, your right isn't connected, you can't use this zero DP. For example, let me remove this line. It can't work anymore because your right doesn't connect to this right. If I put it back, it's work now. I hope my tips and tricks can help you because I try to give you many tips and tricks as I can. Just one more thing, we should say gave, Why? Because the text, as you can see, it's on the left. I want it in center. Now let's run the app. We waiting. Our app is running, and it is great. Let's continue this on the next video. 25. Day 4: Tools: Tools. As you know, it's a calculator. I want to enter about ten or 20 gets for this result part. I go down and as you can see, I have text in here. I'll simply change it to zero, one, two, three, four, five, 6789. Or maybe 20 digits. It's better and more realistic. 20 digits is enough. Let's see what's the outcome? What is the final result? It is our final result. It's look like this if you enter 20 digits. Let's run the application by clicking run app. Our app is run now. I minimize this and as you can see, it's look like this. Let's stop it. As you can see, the outcome shows me this number on the device and on the final result on user's device, user can see these numbers as well. What I want to do, I want to change this Android to tools. As you can see, I have this now, and that underline yellow underline is gone because it doesn't recommend me to put it on the string file. So let me run the up again. What happened now, we don't have this number in here. But as you can see, let me stop the app. You have it in here. So you as a programmer can see, what is the out come result? What does it look like? It's look like this. But if you create your final app, The user don't have these numbers. User have something like this and empty space. It's really helpful for me as a designer to see what does it look like each part if I have to put them a few string a few data. But of course, we don't want to have the data in our outcoming app. It's just test and for helping us to better design to easier design. Also, if I stop it again and minimize, as you can see, if I remove it, nothing has changed. It's still here, it's the same size. Everything is the same. But we only put this in here to see what will happen. Now, we can know how much space do we need? For example, if 20 digits doesn't fit, we can understand it now. One more thing since we're already here, let me see. We have this. What happens if we remove this line? If we remove it, we have a error everywhere we call tools, and it you can import namespace, so we can understand you use tools and what do you mean by tools? We can import namespace or press all inter. Simply click on that and import tools. Everything's now. As I say, if we want to use anything, we should declare that thing. For example, we want to use the Ts on the tools namespace. So first, we should use tools namespace. After that, we can use tools. Or Maybe Android, we have Android Android Android in here, and we have Android namespace in here. If we remove it, it said, I don't know Android. What is Android. You should import namespace for Android. Otherwise, you have error, so import, and it fix. Long story short, we use these keywords, and we should do something. Andrew Desio knows what are these keywords? We use namespaces for that. 26. Day 4: Variables Part 1: Variables, part one, variables in courtly. Variable is a continuer to assort data values, how to define you write R, your variable name equals value or your variable lanes equal value, and R or kwar R, the value of variable can be changed or modified. For example, first name equals or. First name equals john. The variable name, first name change to John. The value of a the value of variable cannot be changed. If you are sure that the value won't be modified in the future, use this word. L H equals 25. If we give a 45 in the next line or anywhere else, we have error. Variable name rules can contains digits, underscores and dollar signs. Should start with a letter, dollar sign or underline, case sensitive. My age and age are different variables. You see the A, capital A or a small A. They are make the difference. Should start with a lower case letter, and it cannot contain white space. Reserve words, like cutlin K words, such as R, or a string cannot be used as names. What does it look like? It's completed. Our design is completed. Now, it's look like this. I run the project, and as you can see, if I write something and press a button, nothing happens and another number the button and nothing happens. We need to write code to say if we click on this button, what should happen? We open the project and on the project, we open main activity. On the main activity, we have this part and press inter. We write our code for the activity. I want to find this button this button, PTN at, I want to find PTN at on my cut lin code. I write find view by ID. What do you want to find? I want to find Malt material button is here. What is it ID? I want to find it by the ID. First, I want to look at resources. You see there's resources fer. I write R I want the ID, O, R that ID ID. What is ID? You see all the IDs in here. I want PTN at. Look at here, PTN at. This is my ID. So I say PTN at. I just want to be sure so I can press control and click on it. It takes me to that button with that ID. Once more, press control, click on the ID. This is what we refer to. I hope I say all of this clearly because I want sure you know this very well. You find it. What should I do? I put a dot. What should we do? Set on click listener. And as you can see, we have two set unclick listener. This and this. I want this one. In inter, you see all objects that you have in here have unclick listener. Even these boxes for inter in text, these things have unclick listener as the. Anyway, It's really simple. We say sit on click listener. What does it mean? It means, what should happens if we click on this button on this thing, anything. What should happens? It should happens like this. Take this number. Take this number. Add these two together and show these two inside this. This is what we need to do. Take this number, take this number, add these two, and show them in here. Let's do this. We want to take this. What is this? It's text input dit text with the name of EDT first value. What I want to do, I want to find view by ID. Again, find view by ID. What is it? It's dit, dit with Big E dit dit text or to be specified. There's no difference, but to be specified, text input edit text. Text input edit text. And it said you should import text input edit text. You see? If you don't have this, s you should import this Class I imported. So it's fine. Let's clod this again. Okay. Edit text or text in both edit text are both edit text. I just want to show you there's no difference and you can use both. What's its ID? R resource dot, dot what dot ID. I want the ID, dot, then what EDT, You can understand now why did we write edit texts with EDT or texts or buttons with something before them. For example, we write for botms Bt N because we find them easily. Anyway, DT first value, and it's the same. You can easily press control and click on it. You see you refer to what. What I want, I want the value inside that it takes. How can I find it dot what I want text. I want the text inside that edit text. So let me just click here Control C and go to the next line, Control V. I have two of these now, but not the first value. I want for the second for the second. I have edits. First, edit second. It's really common. You just copy a line and paste it somewhere else, so I don't have to write all of these things. Just a part that changes. Now, what, as we say, we want to add this and put them onto this part. I need a place to store the data value. I need a place to a sore my value. Many times that you need some place to restore your text, your values, your number. This is the time when we use variables. Particular and variable, use R. R is short for variable. What should we call this variable? We call it H or family family or last name family name pi n. What do you want to store in this? I want to store on this. Let me just remove this and just name. What type of data do you want to store in this? I want to a store text inside this variable. What is text, we know it as a string. You see the problem. You should write Big S. If you don't write Big S, you have the error. It's case sensitive inside this programming. Now, it's finished. Later on, you can put some value on it. For example, my name equals, you should put a string on this saw. You write, for example, Jack. If you try to put number on this, for example, 23, you have error, Y? Because you can't put number inside the string. See you can put this 23 like text inside that variable, but not like a number. So I press shift and this button next to the inter and go here and do this again. This is a text. It's okay to put a text inside the string, but not a number. Let's me back my name. One more tip, you can put this on the up here when you declare this string. You don't need to use it here. You can easily give this the value when you declare the value able. One more thing, O thing. It said, this is extra. What does that mean? It means if you click here and click remove. It removes the string. Why? Because the cut ln understand you put a string on it and it gives the string type to this name variable by default, you don't have to say what is it. But sometimes you want to be specific. About the data type. Then on those times, you can say what data type you want exactly. Even on this situation, it gives my name string type. So if I say, I have my name, put a number on this. It says, no, no, no, no, no. We Consider this as string. So you can't put inside this string, a number. Also, if you consider this as a text is okay, but not a string. Not a string. We talk about number a lot. Let me have a number as well. He equal Let me see. I have, H equals equals what? 11. Also you can have your data type. What is it int for integer? It said you have an error y because you should put big. And also it said, you see, You can remove it. What if not is okay. Integer is like one, two, three, four, five. You don't have smaller than one on them. For example, 1.5, you don't have 1.5 on this. For example, 111.4. It gives you error. What's the problem? You can use double four. The decimal numbers, you can't have this number inside and in. And as you can see, you can understand why sometimes we should declare what is our number. Because maybe we don't want decimals and we only want int. In those times, we declare what I want. What do we want. Let me remove it. And one more thing, if I say H is equal 23, it's okay. I have repeat this many times and change it a lot. But instead of R, I say, I can change it. Just give the value to this variable one time, not more. This is the difference between and. The difference between R and it's only this. I see on the next video, 27. Day 4: Variables Part 2: Variables, art two. Let me select all of these ED t first input. The data type is a string and it equals two some data. And since as we are in cut, we don't have you this string. It detects what the data type is unless we want to and we need to. Let me just remove this and copy this. Put this in here. This text is going inside this and this is our text. Our data goes to this variable. Let me close this. Before I forgot, I should write that to a string. Why? Because I want to be sure the string of that text goes to my edit first input. Many times many other places. We should be specify to be sure the right data type of data goes somewhere. Just to be sure and don't have any error and problem. So I should copy this to here, and I don't have first, I have second copy and paste sorry paste. It second value and that string as well. What does that tw string does? That twe string goes here and take the string inside of each of these and put it inside my variable. One more thing. You see, we have to a string. We don't have int, even with big o, we don't have to int to a string. Now, let's have our third variable. EDT result is equals to to what. Copy this, paste it in here, los. Copy this and paste it in here. This plus this goes to result. Why? Because we write code for PTN t. Now what? Now, we want this DT result, put this inside this bottom. What is it? This is TC result. Again, I just copy this and paste it in here. Change this part to t x t result. Don't remember, it's not text input, dit text. It's text view with big T. Text view. You see, this is text view. Press control, click on this. This is text result, and it's a text view. So what's next? Next is do do what text? What should we put inside the text? E T result. What is DT result? The result that we store, let's put it inside that text. Okay, let me run the app and see the problem. So we can learn so many other things. Just to be sure, be careful about capital and lower letters. It's really important. Big and small letters are difference ins cooling. Let's run the app. So now, if I put three and put four, I should have three and four equals seven. Let's add them. You see the number 37, T four, it said it's equals 37 y. I tell you why. It consider them as text and put three and four side by side. Not the numbers, not like numbers, like text. First three, then four, put them together, three, four. Because you tell the computer do this. Anyway, as I say, these are text now. So what should I do? This text, this text. Even we do to a string, because they are text, what should we do? So now, what should we do? We should say we want this to be integer. So D to what you see to a string, to wide, too long to int. I want to int. The second one, you see it said, you have in here a string here. Solve the problem to what to integain. Our problem solved, and we have this as a integer. You see, dit result integer. Our problem solved, but wait, we have another problem. This text gets a sing. But we have this int. What should we do to solve this problem? Let me solve this because this text, take text, take a string. D to a string our int, goes to the string, be a string and then goes inside the result. L et's review. We want integer, dot to in, we want a ring, dot to a ring. Now let's run the ap again. I put three inside this, I put four inside this. Last time we see 34 because program put them together. Let's press this button and then we have seven. Three plus four equals seven because it's number now. You see? We also have these warnings. What does they say? They say, you can change it to al, y because you only put the data once inside this variable. So you can use. It's optional, no problem with R, but you can use. I change them, and you can see the three warning becomes one. I solve this three. I see on the next video, 28. Day 4: Functions: Functions. A function also known as a method, a segment of code that is executed only when it is invoked or called functions can receive data, referred to as parameters. They are used to execute specific tasks or actions. Create a function. We use fun keyword, as you can see, and as you can see in the example, call a function to call a function, we write that function name followed by two parentheses like this. Okay. Back to our programming. We write some simple code to take this number and this number when we press this plus button, add them and put them into this part. In our text view. Just this few line of code. Now, the problem. It's not good that we write like this at main class and we write all of this together. If our program became a little bigger, all the codes inside inside of each other and in one place, we easily can get lost inside all of those codes and our program might Mostly, mostly have lots of problems and errors because we can't find what's what. We get lost. Before I forgot, we have this uncreate function. We write our codes inside this uncreate part. When our activity created, these things happens. You can see even this create is a function with this F U N word, you can see this is a function. Let's create a function. I press in in here. I write f because I want to create a function function, my function name. In it, listeners. This is my function name and open and close, and this is my function. Now, what should I do? I select all of these to the end and control X, cut them, Control, paste them 29. Day 4: Errors And LogCat: Errors, and log cat. Okay Let's continue. Minimize this. Let's run the app again. This is our app. I insert a number here. I put this thing blank, and I press this class button. What just happened? My app closed because an error, because I didn't put any number in my second text box. You see this logcat. Click on this. You have the logcat. Make this a little bigger. And you can see this error here. You see just at the bottom. I have this fatal exception. There here. What is it? This is my error. I have another descriptions, but main and the most important thing, this line for this input string empty. Why? Because in this code, I want to make this empty string to integer. I don't have a zero. I have empty string. This makes the error. Even it said, you have this error on where on main activity, Cutlne 26. Line 26 is here, line 26. So you can find out where is your error exactly. Also, you can see in the Android classes, for example, in Java for the integer things and other things. But because we don't want to do anything with those, we just work with our own code and we fix our own problem in line 26. What problem, this problem? Input string is empty. Extra tip. You see this package mine y package mine, because I just want to see my own package. I don't want to see other things. You can press control space to see the suggestion. Let's press control space to see other suggestions. We don't need any other things yet. You can see all of them are here packages or other things. We don't need them yet. Only thing we need to see our own package. Package mine. Why? Because I just want this package name to see what happened with this. If I don't write this, I might see all the other things because this emulator have other things inside. But I don't need those things. I just want my own package. And before I forgot, let's press this to add to favor it. Maybe next time we need it. Anyway, now we understand what has just happened. Let's minimize this and go here. I give you another example. Press inter in here. You see, I have, for example, what? Number one equals what? Equals, for example, 34. This is string. And when I want to convert this string to a number, it's okay. But if it's empty, I have error. If it's zero, it's okay if it's empty, I have error. So I have, for example, 23? It's okay. Even if I put a string after that, I have error. Only number. I can convert a string to number, only if I have number. Okay. Now we understand, what is the problem? Let's cling this and let's continue into next video. 30. Day 4: If Else: E, you have if like this e condition and some code. If the condition is true, your code runs, and you have e, if condition, this code, and if not, the condition isn't true else. This code. For example, you have this e for this value age equals 24. If age less than 30, you print less than 30. I have less than 30, this part runs, print 30 or more, but I don't have less than 30, this part runs. My output is less than 30. Back to coding. So we have a problem. Let's see our app. We want to check if this part has number and this part has number, then we run our code. So let's see if these are empty or not. Right here, before run our code, we write we need a condition. If what? If text utils, we need something from text utils. Text utils is for Android. We need what? We need is empty because we want to check the string is empty or not, is empty. What is empty. Our EDT first input is t or not. Let's check it. Okay Let's go with another way. First, we remove this and then remove this. This is it takes now this variable. You see, it looked like this just right. Variable variable, what, for example, T is what dit dit text equals why? Because we can create variable other than string or numbers. We can create variable put the type of an object like edit text, and we simply put this inside that copy and paste. We put this inside that and of course, text input edit text. It's okay. You remember, we have no errors. We can write edit text or text input edit text. Let's remove this. As I say, we write the edit text inside the variable. Like this and we want to use the own text self. Of course, we should write dot dot what do text. Because we want to check the text is empty or not. Let me just open and close this and press in there. I just continue this in the next video, because I want to show you different things in the next video. I just want to separate this 31. Day 4: EditText Error Property: It text error property. Let's continue. Okay, EDT first input. We have this dit first input. What just happened? This dity first input, the text is empty. So what should we do? You do something about this because it's empty. Dot error. It's a great property error. What should we show inside the error equals, get text. Get text. G text what resource dot inside the resource string. Look at the strings, and then what? STR SCR. I have many SCRs, but I don't have SCR for this error. What should I do? I write the perfect name. In input. I first Input, please I think it's good or in first interfirs. Input. Please error. It's optional. We can write anything like this. Then what? Then we should click on here and click on this Light pub pulp and create a string value resource for this. Okay Let's create this string value. It. What is your value? Please first I think number number just like that. And the check for the Arabic as well. I click. Now the error is gone because I have this. If I open this project, go to the strings. I have string and string Arabic, string. SCR infirst input, please error. Please inter first number. Inside the Arabic, please in first number. You see, No difference. Why? Because I should translate it myself. Let Let's hide it and lose this and lose this. Long story short. If it's empty, give me some error, Whatr, this text. Let's write else. Now, we understand what is it, but how else? This condition isn't true because we put some text inside this. So it runs the else. We write else. Inside else, I want to check second input. So not the first input. This time, second input. So I just copy the whole thing control C. Click here. Control. Sorry, I need space. If it's not empty, check again. E is empty, it first, not the first. Now it's time for guess what. It, Control space, it second value, text. If second value, text is empty, so do what. Is it the first, not the first. Be careful. You copy, but you should change the part you want. If not, you don't give error, you take error from the app. The app isn't work just like you want. The program doesn't give you error, but the app doesn't work as you expect. So be careful. Second value. Finally, I change this verse to take. Second, and it says, Well, what should we do? Create a string value resource. I can use this light bulb or click in here and it says, what is your value? I check the Arabic as well. Please in second number I press this grades, again, let me check. Please inter second number. That is first number, is second number. Please inter first number, please inter second number. As I say, we should translate Arabic or any other language. I just write Arabic as an example. Finally, L. What else do This part, if the first input have something and the second input have something, has something, Now it's time to add them and put them put the result inside the text view. Oh, I have this error. Let me fix this dot dot what two string. Then two in. And again, dot to a string, then two in because our in needs a string. Let's run this up. Click in here and wait. Okay minimize this and zoom, this, and I don't inter anything. I just make this a little bigger and click here. I have this error. I click on this. Please inter first number. Oh. So this tells me what should I do to fix this problem. It shows me this string first input. Okay, 22. Plus, another error. What is another error? Please inter second number. Okay. You see it catches me inside the second. Now, what should I do? Inter a number 22 plus one equals 23. Let's press plus and crashes. Why? Because we have error. What is the error? Let's open this cat. Open L cat. I have this and I'm going up up. What does it say? It say for the input string, number format exception. For what for this input string? What is the input string that you can't exchange it to the number. This is our input string. This isn't a number. It's text. Why? You see, this is our text, and it can't convert it to number. Before I forgot, you see this, you see another thing in here. But I don't want these other things. I can simply write. Okay. I want to write level. Let me just press control space. You see? Control space. It shows me this guide. I want to write level. Age is message level. This is level. Inter level. Level, what I want error. Or I can press control space. It shows me. You have level of this, this, this, this, this, and this. I want error, instead of typing that. So what just happened, Level error, and space and level error. What does it show? You see? Just the errors. Nothing else, just the errors. Because I want to find all the errors. I make it simple. Especially when you have lots of messages and you just a specific thing. You see? I say package mine because I want just my package package, and I say level error because I just want the error of my own package. And if you have lots of error, you can right click click, clear. Li cat, it clears all these and you run the app again and exactly do that thing to show the error. So you don't see error from 5 minutes, 10 minutes or 1 hour ago. Just from now, I can clear it like this click, clear and go to the app, do the thing and have error exactly for this part of time. Another thing, as I say, you have this line 33. Why? Because you have this error in line 33. We don't do anything with the Java codes. We have this part. We work with this part, line 33. What is line 33? This part. We have error in this. Even if I were here, I'm here now. If I click in this, it takes me to the main activity cut line 33, the exact location of my error. We know the reason. We know the line. What is the problem? The problem is we convert this edity first input to a string. What is this edit first input? This is press control and click. This is text input edit text. You convert this to a string and then try to convert it to the number. So You can't convert this this a text to the number. You can't convert it y because it's not a value, it's an object. So, I understand what is my problem? I should first say, I want the text of this DT first input. Then make that text string, then make that string an int. So this is the same. First, take the text, and then make it a string, and then make that string an integer. I hope you understand. This variable is an edit text. This is the problem. One more thing, I can use this with Big i integer dot value of value of this string value of string. Let me just cut this and put it inside this and I don't need this like this I make this string as integer, like this. It's equal. Let me just crest inter in here so you can see this is equal of this. Okay. I can even press inter in here, so I have it in next line. I can write to directly or I can use Android method to do this. Okay. Let's run the app. But first, as I say, you see right click Clear like ca. You clear it like this. And now if you have another error, you can see that. Let's run the app. I have first number. I don't put anything. Click here, I say, please interfer number. If I put any number, the error will be gone. This error property is really good. It's for text input. This edit text. I write 22. It's gone, the error is gone, and I pressed plus, I had another error. Why? Because it's empty. I write one. It's gone. I press this plus pattern and I have this 23 in here. 22 plus one equals 23. 32. Day 4: Minus: Minus. We just use this four PLS. Now it's sim four minus. From here, find V y ID. Let's copy this. Control C, er control. Now, I have copy the previous codes, exactly the previous codes. First thing we change PTN, no Pt n minus. You see this part, you have the plus. You don't need the plus, you need the minus. It's really simple, It's really easy. Let's start the app, run the app, minimize this and write seven minus three and press this minus equals 47 minus three equals four. If you press this plus equals ten, but if you minus equals four. As easy as this, you write the minus code. I think you might say, why don't we repeat many of these codes, for example, This edited first input and this edited first input, we have many of these things. Why we repeat repeat these codes? Why we use thes many times? Yes, of course, we make our code better, but in the future lessons. For now, I just simply copy this code, change this name and change this character and see how easy can you write code for next button, I see you in the next videos, and I think it's enough for today. Yes, maybe. I see you in the next day. 33. Day 4: Quiz: Day four, quiz. Question number one. How can we create a line in Android? You can write it down and then answer it. How can we create a line in Android? Question number two, what is the difference between margin and adding? What is the difference between margin and padding? Question number three. What is the use of the following feature? Tools text. What is the use of the following feature? Tools text. Question number four, what is the use of function? What is the use of function? That's it. You can write it down all of this and then When you answer, check the first video in the next day for compare to your own answers. 34. Day 5: Day4QuizAnswer: The four is answers. Question number one, how can we create a line in Android with a field view and limited width or height? As you remember, we, for example, give 23dp in width or height, and we can have a line. Question number two, what is the difference between margin and padding? Padding, for innerspace, margin, or outer space. You need space around, for example, your button, use margin. You need a space for inside. You need to use padding. Question number three. What is the use of the following feature, tools test to the PLA, the content only to the designer and not in the output version. For example, we need to see if we put 20 digits side by side, how much space does it take? But we don't want to 20 digits be on our output or even in our emulator, only when we're coding and designing. In those times, we use tools text. Question number four, what is the use of function? Grouping code with the same god. For example, I write a bunch of code for adding. I write a bunch of code for multiply. I write a bunch of code for anything else. I use function for grouping them. And as I say, when you have figure program, for example, you have thousands of line of coding. So you use many functions. So you can find the group of code that you need to edit or fix the errors or anything else. And one more thing, I think I say, if not, I say it now. When you use a bunch of code many times it's better to use function. For example, Imagine you need to save something before you close the app. You don't write that saving code many times. You write that code one time in a function with the proper name, and whenever you want to exit the app and save the some status or something. Use that function. I hope you enjoy and learn all of these. If not, please review day four. If you learn, welcome to day five. Let's learn many other things together. 35. Day 5: Review What We Learn So Far And Some Tip: Review and Tips. Let's review. We create a calculator. I just want to see the design of this and yes, just like this. This is our calculator. Where where we create our calculator and we say the layout contains the things that you see on the resources, on the layout. O. This activity main contains the things that we can see. I mean this page or this view. I should say. We call these pages activity, and in the first lesson, we create this project from zero under Catlin, under our project name, we project package name. We create this main activity. For this main activity, we create a layout. We talk about the activities that each activity has a layout. This part has the code, this part has the design. We understand that this XML contains our layout and we talk about how we can see the design mode split and or just code. We talk about constraint layout, and also linear layout. That looks like a line y. Be the objects inside linear layout, They are oriented. They put together, they shows together like a line vertical or horizontal. After that, we create these two boxes for input in texts, and these buttons. We talk about these materials and why we materials. We say the own Google, the Google itself introduce material. Because material designs makes up in some ways better. As you remember, we create these buttons and since we want them line up together, we create this linear layout and we make it horizontal. And also we talk about the weight because we want our side to be by weight. We also create a line by this view, we create a line. We simply give this background and a height so we can have the line in this place. We mentioned that we have this background for this view. And we also say we have this background for all the other objects. At least most of them. For example, we can just copy this and pre inter paste in here. You see. Now we have this background for this text view like this. There are other properties like this background, like padding, like this set hate ID that are common between most of the objects because most of these objects has these properties. And since you can understand how you use this ID, you can use it in the other objects. We can call them common properties or regular properties. We also create this text view and this text view because we want to see the final result. I have a few rules. I recommend this to the people. I put ID first. For example, wit and height next, and bottom up sort of at the last. I recommend you write like this. It's easier to find things. It makes many things easier. And I do this in many other ways. You can see ID first and then Witt and height. And When I want to find the ID. I always know, I put the ID first. It's really helpful. Or the other thing, you see, I have these texts. I have this text first control. I have this text. Let's see on the main string. You see all of these has this STR, SCR SCR. Why? Because it's my principle. It's my rule. It's easier to know, it's a string. And it's easier to find when I want to search for this you don't have to, but these rules makes things better. And also, we have this layout, as I say, we have this values, diamonds, and strings. This string is default language, and we also add an Arabic language. You can add any other language or you can have different default language. We put it English default. Our default language, put it in English. I just copy these three lines, paste them into Gu translate and copy and paste the results inside these three lines. Why? Because I want to translate the others. This is Arabic. It shouldn't be English. Let's close this, let's close. One external note, you can even have click for these for this or even these. All of these can have click. But as you remember, we just put for these buttons. Most of the time we use it for the buttons, but you can use it for the other things. As you can remember, for that clic. We should define that button, find it, and define that k listen. For finding it, we use find V Y ID and find that button. My button is material button. I should define what is my object that I'm going to find. Where is this? I press control. Click on this. This is my TN ad. What do we want to do when we press this button, we want to add this with this code, you can see, we find out each of them and add them together with this plus and put them inside this tit result. I recommend before start typing, before you start typing, think about what you want to do. For example, first, I decide I want to add these things, then I start coding. And we talk, we must find each of them, so we use find view by ID for each of them. First input n, second, and also we check, are the empty? Is the other one empty? If not, let's run the code. Also we talk about this error. How can we show error? It's enough for the review. Let's start coding and continue the course. 36. Day 5: Gradle And view binding part 1: Gradel and view binding part one. Welcome back. Let's go to the code. Open main activity. You see we have many fine view by ID. To find the object. I should write all of this. Isn't there any easier solution that helps us? So I don't have to write this fine view, fine view by ID every time and go to find that object. There is an easier way. What use view binding. What is view binding? Vew binding helps you don't you have to write these fine view by IDs. If I want to say I want to click on this button, I don't have to write A code and it's makes easier to find my object. First, gradle. This is gradle part. This file, you see that? This second file with this name. Be careful. There is the same name just up in here, not that module app, not that project, module app. Let's just open it. Double click. We open this. What is this gradle? If I want to use thems and libraries, first, I should define them in here. For example, we want to use view binding, first. But first, we should define it, then we can use it. Where should we do this in Android CDs Android section. Open it. Let's go down there in here, inter, inter. Let's write B. I write just a few characters of these build features, and it gives me all the things that starts with build F. But just be careful. If you write, for example, O, You can't find it anymore. You can use android studio hell, but you shouldn't write anything wrong. Careful and open and close in. We have vi binding, and it's equal to what true. Y because we want to use it. So what happens? What is this light? Sync now, y? Because we change our gradient. We should sink entire project. So I can press this just like this, press this and sync now or at the top, you see it says sync now. Why gradle files have changed. So you should syn, press, and wait. Okay, it's finish back to our code. Okay, we're going in top just in here. So what should we do? Let's define a variable. We can use or. We use. What's the difference? You should know. If it's, we can give it multi different values, but just one time takes the value from you. Of course, if you forgot these things, you should review earlier videos. So what's the name? Binding. Activity main binding. Is this a important name or code? Why it's activity main binding? Because My ML is activity main. So I want activity main be bind. Whatever is this thing's name, my binding is with that name. For example, if it's activity about I should write activity about binding. What's next? Dot inflate Layout inflator. Okay. I have some problem with this in plate, and it gives me error. So what should you do? I make this simple solution that I just did. First, I go to this menu. Go to build. Press, clean project. Clean project, press it, wait until it's finished, and then then what file come all the way down. In validate caches. Why it takes about I think 30 minutes at least for me. And I have to search about some other things and got confused. After these years of coding. Even me. So be careful. Check all of these three things. If it can't help you. First time you invalidate and restart. You check this. Check this, check this. Clear everything, invalidate and restart. In the first time, because I forgot it might because I forgot. You can't be sure. Might because I forgot. Check these three. I'm not sure which one of them do the job. And invalidate. It doesn't work anyway. I check at last, I check all of these three. And first, first of all, I restart my system at the end. After reasserting, I do all of this again. First, I came after reasserting, rebuilt, sorry. Kian. After Kian, go. And invalidate. And then I think maybe this can help check these three. Why? Because it clear everything. Even file system cache. It clears everything and invalidate and restart. Check, check, invalidate restart, and then I just rebuilt Then I saw this where is my error? It's gone finished. Everything is good now. Anyway, I might make this part one a little shorter because I at least take half an hour to find out what's wrong. Please take a note of these three steps. It's really important. Sometimes even professionals, programmers, Make these mistakes. It's a really simple mistake. You see? I repeat one. Simple mistake. You and say, Okay, I invalidate, and you forgot, check these and you confused because error isn't gone. What should I do? What should I do? I can't find it. Anyway, let's continue. I hope this, this one thing helps you a lot because it helps me and many other people and restart. I'm not sure maybe restart can help. If it can't help, first restart your computer, then do this. And remember, sorry, remember, you should connect to the Internet because it takes the library again. I almost forgot to tell you this. It's important. Now, where were we? We activate our binding, and if I press control, you see, I press control and click. I go to activity main. Press control. Where is it? It's here. I'll show you one thing. You see this activity main. If I press control, click, come here again. So it's equal this equal this longest story short. This is my activity main. This is my layer, but it's binding. So we create a variable That contains this activity made. Set content view, set our view to this code from this layout resource because our activity contains two part one is this cout code and two. This layer, this view, the thing that people can see Now, we want to join them together, so we say set content view for this code. For example, let's add layout new and layout resource file. Click. What should we call it? Let's say Login, just press. We add it Let's simply add a button, button and to here and this and this and this to here. You see you can do this with the design mode. You see here, design split code. It's design. Simply open this common button, the drag and drop the button and just like this connect the dots to the corners. Y we write code, because it's better because it's more specific and I prefer that. But after the course, it up to you, you can use this. I prefer write those codes. Maybe in the future in the course, I do the design mode so you can see more of this and you can decide them. Let's see the split. What do we have? All of these codes. Now, if I want to set content view, for example, log in, I can give log in to this and press control and click for going to log in. Why? Because it's logging? No difference. We can comment this. Do you remember comment? What is comment? When I comment a code, we don't consider that as active code. We just write it for ourselves. Andre D Sudo doesn't care what do you write in that code. You can write whatever you want. Even write stars, peels, all the things you want, or write. For example, you can write this line do that. As I say, Andre D Sudio doesn't execute the comments. Ignore them, like all other programming languages. So let's run the up to see what do we have. I run the app. It gives me error. Of course, why? What just happened? You see. You want to run codes and find V Y ID that you don't have in that log in. Anyway, long story short comment, and running again. This is what we have. This button, and this is the login page. Stop the app. I do all of this to show you what does this set content view does? It sets our layout view. Instead of this, show me this and Ling a story short, this is what I want to see. Let's continue this at the next video, so we don't have very very long videos. 37. Day 5: Gradle And view binding part 2: Gradial and view binding part two. Where were we? We talk about set content view and what does it do? Let's delete it. I press delete on my keyboard. I click. Now it says, I don't have any log in. I change this to activity main. Now let's remove this comment, and we want to this content view, take the values from this binding that contains our activity main. Do you remember activity main binding? We bind our activity main. The first thing is we cut this control x and inter control V, y? Because we want to use this inside this. Now, we say, we define this control C and inside this control V. You set content view from that binding You should write declaration of your variable before the place you want to use it. Now, we write that. You see, if it doesn't open this help. You can, for example, if I click somewhere else and came back here, it doesn't give me that help thing. I just press control space to open this or simply write any letter for the thing I want, for example, I write R Y, because I want root. Now, instead of doing all of these things, I can simply write something like binding. Inside binding PT N. Do you remember why we write PT N before buttons? Now I have my four button. If I write other things, for example, just add, I can't find them this easily. I write PTN before the button names. Now, I want to find all of my buttons. I simply write PTN. I have the list of my button. The rules, the structure of the naming that I told you, There's a very strong reason for using these rules. It's really important. You can have your own rule, but you should use the rule all the time every time. I write PTN. So I want my button. PTN. Where are my buttons? You have these four button. And I want my PTN ad. I just go down, down, down inter. PTN ad. Inside that PTN ad, what do I want? I want set on listener. It's easier then find view by ID and other thing. Agree, and I write my code inside here. We write it instead of all of this code, we simply write binding and this a PTN ad, instead of all of these codes, binding. And of course, after that, set on listener. You might say, why didn't I show you this in the first, why I bother my myself to show you this kind of code. Why didn't we just write the short code instead? Because you should understand all the way that you can do the things and you can decide in a certain situation, which way is better. You should learn. This is fundamental. This is basic. You should learn these things very, very carefully. Because of that, I tell everything specific and with very details and examples. So please please learn these things very carefully and very good. Let me give you another example. Next line, you have. Find view I move it it in here. Okay. Find view by ID. Text input, edit text and other things. All of these things, I want my Edit first value. Do you remember Edit first value Edit first value. The ID. Is the name of that object. I want this DT first value. What should I do? Instead of all of these? Let me show you bind D, D. This is very good. E. Why should we write DT? We can use anything, but if we write D t in the start of our edit text, we simply find them. This is our two edit text, and simply inter This code is equal to this. All of this became this simply, easily. As I say, you should learn both the ways. Very carefully because this is fund the method, very, very important. Before I forgot, I should remove this comment as well. This is my method. This is my function. Okay. Let's write binding and replace all of these things. Let's go. Binding Bind D. What just happened? I said, I don't know any binding. Where is binding? We don't know binding. Do you know what just happened? We declare our binding. This is our binding, and the use our binding, but with the same name, you see Control C. Exactly, I just copy that. Control V, paste that, but I can't use it in here. The U say I have the variable, the name binding. You can use the binding, not before that. Do you remember? I just said if you declare this binding, you can use before that declaration. Because of that, We move this line of code from down here to up y because we just want to use it next to it. Please, please pay attention, learn these things very well. These are very important. These are all fundamental basics. You should know all of these things. I'll repeat this. What is this? Val, val or Va, we declare our variable with this. After that, the name, we say the name of this value variable, sorry, variable. The name of this variable is binding. So after that, we can use this binding, and even the thing inside of that binding with that. And then after that, we can say Again, we want to use that binding. And even if we open another scope in that area, let me say just area. Inside the new area in here, we can use that binding. But above that. For example, in here, I can't use that binding. See, if I paste it binding in here, we just not declare that. We just don't introduce that. So nobody knows what is this. We should first S, what is our binding. Okay. Just like that, You see the open in here. Just in here, yes, just in here and you see this line all way down. We ellos in here. Open ellos. This area. We say our binding is exist, but only this area, only in this area and and After we say val binding in this area and after this val binding, not before. When we close the area, we can't use that binding anymore. Let me give you one more example let me say or this time, R H equals 22, and I say, I declare my variable, I want to use in here. Can I do that? No, first, This is inside this and second, I use it before declaration. But if I say, this variable in here, it's okay. And again, if my age goes outside the area, there's no ge in here. Nobody knows where is the edge because we declare that in here. So to close this. We have a function and we can use the things we declare inside that function, only inside that function and the functions that are inside of that function, not outside. Before I forgot, I say we declare function with f. This is the keyword. Let's clean this and also this. Let me fix this problem in the next video. So our video doesn't became very big. 38. Day 5: Gradle And view binding part 3: Gradial and view binding part three. We want to fix our problem. We should use our variable globally. Global variable is a variable with global scope. I mean that it is visible throughout the program. It has many levels and we just want to see this variable rough the functions that we need. Let me show you. As I say, if we declare a variable in this place, we can access it in this area and because we declare it in this place, we can access it in this area. So we go up in here, press in inter inter in here, right, w what al binding control C control V. Then what? Then the type. What is this variable types? Type is its activity main binding. It gives me error because we didn't give this variable any value, and it says you should give it some value. We fix this like this que mark equals null. I just said you didn't have to give this variable any value. Just leave it. I know it's the rule. I must give this kind of variable value. But for now, just leave it. Because of that, I give it null. Null means nothing. It's not equal zero. It's not a zero. It's nothing absolutely nothing. It's empty, not a zero. U, it's not equals to zero. Why we did this because we want to give this value, but inside and create when we create our class, we want to give this binding our value. Let me show you, if I want to do this, I can simply control C and give this value It's okay. But I don't want it like this. It. It's fine. You see. I want to be nothing and later I want to give the value like this. In the tl, it's the rule. We want to have a global variable. Global variable must have a value. It's the rule in cat. This language have this root. But since we don't want, we should do this trick to let it go for now. What? Remember, you must give this thing value. I suppose you ask me, you give this variable. I see that. What is this Why you put a question mark in here? You see you must say my variable can be null or not. By default, it cannot. But We add this question mark. You see if I remove this and give this variable and null. It gives me error. But if I add this and say, it can be null. It's okay. I have no error. Let me give you another example. Because we want to do this first project and basic fundamentals as best as we can. Let's go. V, what, give it name. This is a name. Name what. For example, it's must be a string. I just say, I say it's a ring and I say it's equal to null. But I have a problem. Did you remember, you must write these things with capital or be. Sotlin is case sensitive. So you must write big capital S. If you write a small S, it's not a string. Just remember. Anyway, what does it say? Null can be a value of a non null type string. H. What should we do? We say this F name first name can be nu. It's okay. If we don't say, it's strong. But if we do say it is okay. Okay, let's clean this and give it space, and Extra tip. Do you remember we say you can skip the value type? You don't have to say, what does these things value type? Do you remember But just in case, you give that variable the value. Cutting can decide what is these things type. For example, if I say, F name equals to, even an empties string or just space or a few characters or any other thing. It's okay. But when we want to give it null. No, it's not okay. We should say what is in these things in the future. Even if we give these things number, it recognized it's a number. But when we want to give it null, it can recognize. Cotin is really good because it can recognize what kind of variable is this. But only when you give something to this variable. I remove this and extra example, as you can see, we have this binding, and we didn't have to say what kind of variable is this because we right away give this thing value. It says, yes, it's activity main binding. Long story short, when we give null, we should define what is this because it can't decide what is null. So because we defined it in here, we don't need this val. And since we say val, we can give this value variable another value. Y? Because we use val. Do you remember difference between val or V and V, take one value. V can be rewrite many times. So to fix this, change this va to va. We continue this at the next video. 39. Day 5: Gradle And View Binding Part 4: Gradial and view binding part four. Welcome back. We have some errors, red line for that error. You can see the description of that error. What does it say? I say? The variable that you defined can be null. It's not null. It's not definitely null, but it can be null. Because null is nothing. This part said, I don't accept nothing. You should do something about it. You can't send something to me that might be nothing or as I say, null. What should we do? I just came here after that binding, put one and two of this sign. If you press shift and press number one on your keyboard, you have the sign. Two of these I just write and the error is gone. What does it say? It say, let it go, or simply you tell that error, it's okay. I'm sure it's not null. Why I do this? Because I'm sure I give some data. It's not null anymore. So I can say, let it go. Oh, we just put two exclamation mark. I think y pronunciation is wrong. What exclamation mark as I remember, and the error is gone. Please forgive me for my low English. We have two more of these. What is this? It's just my examples. So I remove this and everything is fine. Let's continue. Now, do you remember we just use this Y? Because it's sallow ball. It doesn't end here. What can I do with this scallo ball variable, select all of this. I just say bind thing in there. T t n. I have my four buttons. Tn add that the one I want. Just like before it says, it can be null. Your binding can be null. I say, I'm sure it's not null. Let it go. Why it's not null? Because I just said it has a value. I give the value here. Just so you know, your program goes from to to down. What it means? This line is running, after that this line is running, after that this line is running. After that this line is running, that we say, we have the value. So before this line, our function, we give the value. So it's not not. It's always top to down up to the bottom line 21, after that, line 22, after that 23 24. It's okay. Because we want to learn very well, let me show you another way. We can use This question mark and in here, question mark, it's also okay. What is the difference? One way and second way. We have two ways. What's the difference? If we give it question mark, if it's null, it doesn't give you error and just forget about it and leave it. Just ignore it. Yes, et cetera. Just ignore this set of codes. So when we say this question mark. After the variable, that can be null. Where is it? That can be null. So I mean, if it's not null, do the job, run the code, but if it's null, forget about it. So ignore no error. So you remember, if you write this, you have error if it's null. But if like this, you just forget about it and ignore it. The program ignore it if it's null, no error. It gives you error and stop the program, but it doesn't give you error and just ignore the code. Entire code from here to down there. Ignore the whole thing. One thing is good about you learn from a programmer that wrotes other programs. I can give you advice. I tell you, it's better something like this. I tell you, it's better. You use this question mark. Many times, I use this question mark instead of this Y. So during that if my programs running, my program doesn't crash. And you see the point. I I don't write it in here, it it's okay. You say if binding is null. Forget about it. But BTN can also be null. So I say, Okay, if it's not null, continue. Because of that, I have two question mark, one for that part, one for this part. You might ask, Okay, why didn't I write this question mark in here? You see it's okay. Let me remove it. Okay. It has error. Now, it's okay. Why? Because I want you to see the different way to do things. It's really important. You learning is really important. And from my experience, I only use this type of ignorance. When I just give the value. You can do it anyway anywhere anytime, but I just use this kind of it's okay. Then I just in the one or two line before give the value. I'm sure this isn't no. But the other times other places I always use question Mark. This is my experience. One last thing. Why do I have this much repeat on this because of course, you have, let me see, 66 line of code. Many of them are just in there, maybe 50 line of code. It is a really a small project that we made, so we can teach you better. But imagine just imagine instead of 66 line, you have a big project in the future with 66,000 of lines. You like it or not. You can have many of these problems. This kind of rules for your own good. These are really important. Imagine that kind of project have error and everything goes wrong. Stick to these important rules. I hope you'll be okay. Let's continue and have many binding like this. I just minimize this to have better view. Now, in here binding, and the question mark ptn minus and another question mark. Just like that, you see, it's simple, simple and similar. Now, in here I have this. Let me just Commented. So you can see binding dot, just so you don't miss and confuse to what should I write? E t first value. D first value, D first value, and of course, our que mark. F edit second binding mark dot ED, second value. And we even don't have to put it in separate line. Just go here and press or select and remove. Why? Because it's much smaller code and we don't have to line. You see, we continuously repeat binding binding binding. Binding in here, binding in here. Or even in here, we should write binding. Isn't there a better way? Please remember all of these things. But keep in mind, isn't there a better way? You should learn all of this. But from here, we have this question. So what can I do? So I don't have to write these many bindings and question mark and many things. Make it easier. Let's go up in here. Now, in here, I press tap tap. If you press one space, you go this much, but if you just be here, for example, and press tab, you jump to the next section. In next section, what do I do? I write. Finding. What's next? Question mark. What's next? Dot. This is a good one. Apply. What just happened? We write this app. This is a great Android C cut code. This is a great code that Android studio in Catlin provide for us. Let's just from here to all down. Control x, come back here, control, and pace it. It helps me that I can remove all the bindings, how like this. Just look. This is the binding binding question mark and dot remove. Binding question mark dot remove binding question mark dot. Let me just comment this and control C and in here control. Because I want you to have the examples. You can do this in your code as well because I'd like you to know all of the different ways. Let's continue in here remove. As you see, we don't have to write This question mark, and it's yellow, y, because I just say this binding isn't null, run this code. What is this code? All of these codes? I don't have to check it again with this question mark. I I remove it, it's okay. If I remove it, it's okay. No more question marks in here, if it's null, none of this code will be run. Just I have to write one question, Mark. I hope you understand all of this. If not, please. After this video is finished, review this video. These are really important tips. And if I don't write it in here, all of these are rank. I have to run it. Now, let's continue. We have this text result. Just double click and control. I want to replace it. Select all of these and control. Just like that. You see the second way? I just double click Control C, select all of these. Control. Double click control C, select all of these, control and remove and space because we don't have to line anymore. It's really smaller. You see how short it became how better it became smaller, it became. Now, down here, double Control C and of course, control. Let me make it even better. We have this Difers value. Yes. What if we comment this and comment this? First value, control C, first input, first input, and first input and second value. We have second value, second value, second value? We don't need this anymore. We can just remove them. And again, first value in here in here, in here. It's really smaller. I just can copy this control, x and go down here in control. You have the code in here, so my code isn't really big. I close it again, sort my code even I can copy these control X and put it in here and don't give the value my result. But I keep it this way. Why? Because I think it's more readable. It's easier to understand. But it's okay if I just control, this and put it in here. Like this. Let me show you, let me show you Control C, and t xt result tx is equal. We should open like this and string. It is okay. What I prefer this one. First, I give the result into that value variable and after that, the value in the variable, I put it in the takes the result. It's easier to understand better. Let's continue this into next video. Thank you. 40. Day 5: Coding The Other Buttons: Coding the other buttons. Okay, where were we? Let's add the other two buttons. Copy the whole code. As you see, inter and control V. What does it name? P t n, multiply, what else do you see this minus in here? We change it to the star or multiply. We can select it and copy this or we can use the code. We already copy. Inter Control V, pace another minus. What is this? P n. We have four btn, btn, d, and what should it be? Division, we change. This part and this part. We have division as well. Let's run our application. We press this between button, run the app. We wait. Our app just launched, it took 6 seconds. Hide this Because it's a small app. It just took 6 seconds. Maybe bigger apps take 20 or 30 seconds. Okay. Let's try and see what do we have. If I put seven and put two, add them, what do I have? Seven plus two equals 97 minus two, equals five, seven divided to two equals three. 3.5 but since we have integer, we don't have half. So 3.5 is three. I think in the future, we fix that as well. Anyway, and multiply seven multiply two, seven, seven equals 14. All of our four buttons are good and fine. Okay, I don't have the seven. I say plus. Please inter first number, minus inter first number division first number. Or if I say two and say multiply two times two equals four. But if I remove this two and say multiply, please in first number. I put four inside this and remove this one. Check it again, division, second number, one, division, four minus equals three I, three, But if I don't have this minus, please in the second number. It worked great. It's good. It's worked just fine. We stop our project, and in the next video, we make it even better. Just remember. Our purpose is not to make this calculator. We just make this calculator to show you the basic fundamentals, so learn it very well. 41. Day 5: Returning Values from Functions: Returning values from functions. Let's continue. We have this PTN ad, and we have this part. So check if there's empty input or not. If we copy this and press control F and we paste it, it's just pasted for me because I just copy it. Anyway, let's check. We have just the exact code in here. We have just the exact code in here. We have just the exact code in here. What just happened? I have one, two, three, four of the same code. It is really bad why? As I said earlier, imagine, just imagine you have 92 line of code in here. But what if I have 10,000, 50,000 or even 100,000 lines of code. What then, if we just repeat the same code, not four times 100 times. For example, if we imagine these eight line of code, five line of codes, is a 5,000 line, 5,000 lines of code, if we'll repeat that 5,000 lines of codes. Ten times we have 50,000 lines of codes. It is 45,000 lines of codes for no reason. And if we want to change things inside that code, we have to edit in here in here, in here. Is there a better way? So we change the code in just one place, and we don't have to change it. Even if it uses 100 places, we go to every one of them and those exact things in 100 places. What if I forgot one or two of those 100 places, I have error. So we shouldn't. We must not repeat the same code. Let's use function. What is function? It's a function. What does a function do? Function is a bunch of code with the same purpose. For example, this function with this name, with this fun for introducing our function, The job of this function is sit on click Listener. Because of that, I say in it listeners. So I know what does this function do? You can put any name, but you should give the function a name. That you can understand what does this function do? Because when you have more functions, you might get confused. Name them carefully. This is really important. Let's continue. Let's go down here. Where does this function open in here and let's continue this line this line, this line, this line, this line. It ends here. You see that over there. You see that. Let me again click here here. You see that fun up there that appears. It says, This closing part, it is for that function. So because I don't want to start a function in another function. I press inter to make it separately. It's another function. What should I write? Function. Function, what? What do we want to do? I can't give this any name. And just like that. In here, this is my function. What does it color? Why should this function colors gray? Because you never use it. Because of that, it look like this. If you use it anywhere, even once, it's just fine. For example, you see, I just copy this, paste it in here, and it's fine. I remove this. Let's continue. But we want to try another way. We create function like this. We want to do another way. So I remove this. Let's go up up up in here. Before this press tab to the next line, tab to the next line, tab to the next line, tab in here. Let me check it again. What does these codes do? They check? Is it empty? Let's call it not. Do you see a small and capital n t value y, B it's going to check this going to check. Is it empty value or not? Y value, inputs. Puts is not empty inputs. So open, close. You just press shift and number nine and zero. What does it say? It say, you call the function is not empty input. I don't know any. It's right, because we are not defined any, it's not empty inputs. We just create a function, but we delete that function because we want to see. Is there another way? Yes, there is. What do we want to do in here? We have this light bub. If you click on it, we have create function, is not empty inputs. And if we click on here, on this and press inter. Press Alt and inter. If we press Alt and inter, these things opens. Let me try again, Alt and inter. These things opens or the light bulb. As you can see, under that rights. Click or press all plus inter. When this things opens, I just click this and it creates for me. Function is not empty inputs, easy, and even it writes it to do for me because I should write some codes inside. This is private, so you can't access to this function from other classes. This is function. So you can call it inside this class many times, even hundreds of times. It's okay. This is its name, and let's continue. I tell you about this part later. Okay. I just remove this part because I just want to start coding. So let's go up, up, up. We have these. Just control C, I just copy these or control x, why not? Go down, down, down, paste in here. We don't have our binding. Let's go in here, press inter and write binding question mark do apply, and these all goes control. In here, control inter. Let's close this again to be sure it range well. It. As you know, we just finish our project. Our project works just fine. But we are not intend to just create a calculator. We want to learn other things. Because of that, I continue to coding other things to make our code better. What I do, I check if it's empty, put some errors if it's empty, put some error. Now, let's go up in here. I just control X and say if shift and nine control V, Is not empty input. If it is not empty input. I check my function to see it is empty or not. But we have a problem. What? It's not true, It's not false. If works only true all false. So inside this if I should have a condition. I don't have any condition, so we have a problem. We have this light bulb. I press on it. What does it say? Change return type of call function to Boulan just like this. This wants to make my function, this function. As Boulan this function returns blean, true or false. So let's go up and say, Okay, I agree. Let's make it Blean. Error is gone. Go down here. It's Boulan. This is the difference. Though my function returns Blean now. This function do something and return returns the result. I have an error in here. What does it say? We need a return y because it should return true or false. Fulan can have two values true or false. I click in here and say T, T, return False. If we reach in here, we return false. Our error is gone. But we shouldn't reach top down here. Why? Because if there's my e, I reach here after else, I should return through Just in here, I should return true. I say everything is good. So I go down. I say else, return T, it's not empty, it's not empty, so return true. Anything else, return false. So I go up up up and say, if these things is true, do the job. I remove this s, if it's true, do this job and close it again. I sort it. If this is true, Calculate. I do this with this function. I just copy this. Control C, go down, select all of these. Haste. If it's true, do this again, and it, and again. Control. I have zero results. Y Be I replace all of these. Close d. I have one, two, three, and four calling that function. I call that function four times. Instead of repeat this code four times, I write it one time and call this four times. Let's run our application to see what do we have? Until here, I just want to see if everything is okay. Press this run button. Since I already run the app, just run my app under a second. So I just press plus, please inter first number. Oh, it works. One. If I press minus, please inter second number, one minus zero, five minus one equals four, what about division? Five. What about if I clear this five, multiply? Please in first number. Seven, multiply four, multiply 28, it just fors fine, stops up, minimize it, and you see We do this all with this function, we don't have to write it four times. So we have a bunch of code that do a unique thing. What is this unique thing? Is not empty input. Tucking is not empty inputs. If we return true means, is it not empty inputs? We say true means yes. If we say false, means no. Do you remember if we press control and I want to see what is my Dity first value. Click. Again, press control and click to see what is this? Click. This is Edity first value, the first edit text, and we return value. Why? Because we want to return, what just happened? What's the result and it's bulion. So it's true or false. Not a number, not a string, true or false. You remember, if this is true, we're not going to Eels, we jump out. What do we What happens if we jump out? It goes down here. It escapes all of these. So this else won't run, so we go after it. What does it have? False. For example, if this is true, we don't have this, false. If it's true, we don't have this false. But if we can go to the else, return true. If we return anything, we're not going after If we return here, we're not going after this, we won't return false. It stops in here. Whenever you return anything, you stops in there, and you won't go down. For example, in here. If I write anything else, for example, return to ro, it gives me a warning. Why? Because this never runs. You return false, and this never runs. You see, reachable, you can't reach there because you return in here. Whenever you return, it won't go any farther. It just stop. I remove this. I hope you understand this well. Just like this return, like that, if it's true, these things run and won't go to the else. What if this binding is null? We have question mark. So All of these won't run, we return files, and we won't take any error. We don't have any error. We already talk about this question mark and what does it do? Let me just show you one more cool thing. You see, to be sure you understand. If you do you remember if we return, the rest of these codes not run. So if we return to, what does it say? It say the other codes won't run. What do you write other things? If you return other codes won't run. And if you see, it said reachable code. Because you make them unreachable in here. The stops in here. You don't have any if or things. It just run and the stops here every time. The other codes worthless. And for sort thing, just close it again and one more thing. Instead of four times, we write one time. Even if we want to use it 1,000 times, it's okay, even if this code instead of ten lines is 1,000 lines. It's okay. You want to use it 100 times, you don't have to write 100,000 of lines. You write 1,000 lines, and you use it 100 times. And if you want to change anything, What, for example? For example, you see we only have one line after the e. We can remove this open and ellos, remove, remove. Instead of remove this four times in the beginning of this video, we just remove it in here and all the other We don't have to do even if we use it 100 times, we correct it one place in this function and all places you call this function. It's okay, you don't have to change it all of those places. I think it's enough for this video. I don't want it to make this long and I hope you understand it. Let's continue into the next video. 42. Day 5: Input Values of a Function: Input values of a function. Welcome back. Let's go up. We have this input. What are these gratings? These are the codes that we never used. You see this yellow thing. This is warning. We have warnings. What should we do? We click on it. What does it say? Unused import, unused import. We have four of these four next to the warning, four of these, and here one, two, three, four. On the line, six, seven, eight, nine, on the line six, seven, eight, nine. If you don't see this, you just click in here. Click, Klick Klick, click, or you can minimize it, hide it. Minimize, and then click. What if instead of line six, I be somewhere else. For example, I'm here, and this is 1,000 line. I want to see line seven. I just click on this. No one click. Double click on this. It takes me to line seven, takes me to line eight, takes me to line nine, line six, just like that. So what should I do? Instead, you never use that unused. So I I, for example, line seven, just select this and remove with packet space, I remove it. What just happened? I just have line 68, nine. I just have three warnings, one of them gone, done. L et me do it again with this one. This one gone as well. I want to show you another way. Do you see this light bulb? Click or press A inter? I just click in here, I just click, optimize Imports. What should we do? Let's just click it and see. It remove. It removes all the unused import where are my warnings gone finished. Done. It's good. Let's continue. Can we create another function? Yes, of course. For example, we have adding here. We just press in there and came back in here. I said, Add Ps. For example, it's not good. Let me say numbers. It's better. Shift nine and we don't need shift zero because it adds it itself. So I want to create this function, give this function two numbers and it gives me back the result. Add them. So I just copy this part Control C, I divide them with this. It's just the button on my keyboard next to the M. I press that control. I mean, the next button to the M right one is this for separating. Of course, for the first one, control, instead of second value, EDT first value. I don't do that with this integer value of. You know the things, how does it work? I just write it in this way so you know. You can do both with dot to int. So I can remove this and I have this ad numbers. One way for creating a function is we just write the function like this, click on it and click on this light b or press A plus inter and create the function with the name ad numbers. So We have this function. What's the difference. This function takes inputs from me and gives me one return result. You see, we return Ban. Now we want to return integer. So I have first, input. I just press tab. It's in Another tab. Second, input. Another tab. I'd like to remain in Another tab. You can't write in with a small. You don't have in with a small. So you should write P and T. These are important. So another tab and finished. This is my private, so I just can access to it from inside that class. Function. So it's a function. It's a bunch of code that I write just one time for a specific purpose and use it as many times as I like. What does it name? It's ad number. I call it. I name it ad number. So I know what does it do? Be very careful with the naming. I'd like to write a small letter to a start and pick letter capital letter for each next words. You can do whatever you like, but I like this way. Same for the variable lambs, as you can see, I write in with big capital I. You can't write them with a small. It's case sensitive programming language. Because of that, you have to be careful with that. I don't like ad. Let me just say it's stum and of course, I have error in here because it expects ad. So I changed it as well. It's sum. Let's go back. So I have stum numbers. So I pressed cap next slide. Another tap in here, I return return return, what? First input. Of course, P second input. It's really simple, one line of put. I just write it front of return. To make it smaller. Even I don't write a variable and declare a variable in here to add them. I just write them front of return, and it returns the int. Close it again and remove this. You can see just like that, returns b return. Integer and we just these numbers. Be careful when you write. This want to return in, you should return in. When you write, this should return Boolean, you should return true or false. You should return Blean. I explain all the function, so I won't repeat it, but be careful. If you just have one input, you don't need this. But if you have more than one, you add this. This character is next to the M on your keyboard, write to it. I don't shift, I just click on, press on the button next to the M to write this. I hope your keyboard just like me. And you can add many others. If you press here, you can add another input what we don't need. Let's just check once more, before just before create the function, we should know what do we want. I want some numbers, and how many inputs do we have? I have two inputs. And what do we want? As I say, I want some Since we return it from this function, I even don't need this variable. Let me just select it and remove it. Select the Control X, pasted in here and one inter in here and remove this Inter in here, remove the values in here. I just want to organize it like this. So sum number, first value, second value to a string. You see how noice and organize this and I clear all of this, and even this. This is how small this can be. Checking empty is a function. Some the numbers is a function. We know our input, and we show our output in text result. This is the whole code for adding. You see how easy and small and well organized is this. So if I have a very big program, if I organize it like this, I have very, very few errors. Always make it organize. Let me just compare that this to this. This is really better. So what should I do? I just go down and say, Let's try this one more time. I don't want to write them up there. I just copy here. Inter control. I have another sum, so I shouldn't write two function with the same name. I write minus and it's gray y because we never use it. We also have one and two input. So we just want to subtract from each other. First input minus second input, just like that. One more time, why not inter and control V? What's this? What is this? It's division D. What do we have in here, division, first input, second input, division, I don't like to write all of this. So, I just copy. I I write up there, I should define the d, the d and other things. I don't like that. I copy since I write it up here and paste and paste and change it. It is really easier, and I enjoy it more. I hope you too. Don't call it laziness. This is more smart. So once more, intercontrol V and multiply and all thing same change multiply first input and second input. So I have three gray function because I never use them. Let's go and use them Inside the if from here to here. What do I have? TX result, and I organize it very well. So I just control C, and even in here inside the from here to here. Control TC result, some. No, not some y? Because I want to minus numbers. Check it out. It's not gray anymore. Why? Because I use it here. The next one, remove here and inside this select this control, we very, very well organized, and this is multiply and we multiply numbers, delete delete. And I have this. One more time came here. Remove this inside the control V and guess what? Division. I just don't want to click on press delete. So select this check. You see the same name, it's okay and these things used. So this is my well organized code functions. I believe A good application, a good Android application, a good Android program is the program that have the least line of code. And very organized. So you minimize your errors. You can I can't make it any shorter. Or maybe, for example, if because I just have one next line after if, I can remove this and this. Why? Because if you have one line after, you can't remove that area, a specific area locators. Just like that. Just remember, it's not four line. It's one line. I just inter. I just press inter. If I remove this inter, is all our one line because of that. I have this one line and I can remove that characters. And I can do it in here and in here and in here, cyli delete. Even now, we have fewer code. Let me show you it's just one line, delete and delete, and just like that and delete. You see, it's one line. I put them under each other to be more clear, but it's just one line. What's next? Remember, if I have another thing in here, I should put these codes inside that start and closing area. If not, my e only consider the first line, not the rest. But in one line it ok. And kilos. Here, remove. And I go down here and right shift and this button just above inter to sort our code or organize them. I go up here and remove this as well because I want to have as much as little coat that I can remove all the extras. This is very better. Yes, yes, it's good. We still have this warning, but it's not important warning. It's weak warning. Let me just show you this as well. For example, it says, property binding could be private on line 11. This is the thing that we talk about. I just double click on it and it takes me to line 11. Okay, I said, make it private. So from another class, you can't reach them. It seems reasonable. I don't want, and it's better don't access them from another class. Okay, I accept this week warning. I can click in this light bu or press plus in and make it private private. What just happened? You can't access this binding from another class. You can access it from all this main activity, but not another Klas. And what about line 20? Okay. Make this function private as well. I came just here or plus call inter. Make this private and I don't have any warning. This is a great code. I don't have any more warning. What do I have in here instead of those warnings? I have this beautiful green check. I love it. Why? Because when I have the green check, it means I don't have any problem inside my code. Even the weak warnings, I took care of them. If I click it, I don't have any to have this green check on your classes all the time as much as you can. This is really good. Try to have this green check. In the next video, I give you some extra tip and really quick reviews on some things and tell you extra tips. I could be sure we don't miss any important basic things. Thanks for watching. Join me with the next video. 43. Day 5: Extra Tips: Extra tips. Let's have a few extra tips and a quick review. Let's review very quickly and close the day. Okay. We create a project from zero and create the activity for our coding. You should get used to activity because everything is activity, and you work with it a lot. How did I make it? Just right click New and then activity. And I click MTV activity, just like this. I just told you, I have this activity, but I also have a layout. Why? Because I should show my things, my data on something. So I have a layout as well. It should be with small letters and shouldn't have a space on the layout name. You see, if I just press space, it says layout name is not set to a valid resource name. I delete it. It's okay. Big A also have a problem. And if I check this launcher activity, This activity became my first activity. When I launch my app. This activity shows itself. I became my first page. And also, we have the select source language. Carlin or Java, we use Catlin oy Cotl because Google itself recommended, and it's really better than Jo. I think it's better than Java, so I use Catlin. Okay, let's cancel this with this cancel button or this Klose button. Anyway, I have my codes inside this Catlin an java, and if I want new, I right click on this place. And my layouts are under the resource. F under the layout. F. This is my activity main. Andre Studio automatically add my main activity in here and my layout in here. Let's visit our layout, double clich. This is my layout. And minimize this. This is my layout. This is my visible part of the project. What should we do when we click on something or the other things? It's not here. It's on cutline file. But in here, we just work with the visible thing. What should we show and how arrange the things. Arrange the objects. Let's just see the cut in file. What should we do, if anything happens on our view? If somebody click on something or anything else, how should we work with datas in cutting language, in this main activity do cut, we decide these kind of things. We have this create method. When does it happens when this activity launches creates be created. Let me say. Okay, Let me back in our visible thing. We have this first number, second number. What are these? These are text input edit text. The user can enter the data inside them. We even give them input type number. We also use material y because Google self recommend this Andrew Studio, recommend this. These are nicer text input edit text with extra features. Instead of regular and basic text input text. You see, let me just go here and write this edit text. We have this simple edit text, but we don't want it because it's too simple. We can use it as well. I don't want it. Even I make them different from each other so you can see there's many different ways to conflict these edit texts. Just remember, this is my text input edit text that user inter data inside. But I have this text input layout as well. I give this another kind of data and It helps to make text input edit text looks better. For example, I put inside this max length, ten, it adds this you see this zero out of ten. It gives me even more beautiful thing and more power to make my text input edit text better. It's my layout thing. But the data data goes inside text input edit text. So long story short, I can't get data inside my Catlin code them this input layouts. I can't do that. I should take it from edit first value. I can't take it from here. Don't confuse with this. This is my visible thing and you don't put data inside it. This text box is in here. It means this thing doesn't have even that text. Let me show you Control C, if I put it in here first value. This thing doesn't have that text. So we understand the user inters data inside this edit text. We also have these buttons, these buttons. We also use material for these buttons. Why? Because it's more beautiful and More recommended. You can do more things with these buttons and read the studio itself recommend this and introduce these. I develop this. I want to put them in a line with each other. What should I do? I use the linear layout, this linear layout. Because I want to show them together as a line. I put them together and I say these should show with each other horizontally like this. We can also stay vertical, but in this case, we need horizontal. We also give weight to each button so each of them can have 25% of the space from 100% of this space that linear layout gives them. Some of the layouts might doesn't support this weight, but linear layout support the weight. Just be careful. You can't use every property you see in everywhere. The whole is one, and we give 25% to each of these four. Also this text view, what is this text view? We want to show data. We also add this view, hide this view because we want to give it two D height, and match parent. What is match parent? The whole space in the parent, and we give it the height two D, and we give it the color black. So we have a lone with black color with the height of two DP with the w, match parent means whole thing. As much as you can inside your parent because we don't have line inside and the studio, we use this. And also, we have layout constraint bottom to top of. We say, we should show this to top of Txt result label. Sticks to Txt result label that we see. And even you can see that arrow that says, I stick my bottom to the top of this We also have an text view. Why? Because we want to show our final result inside this. We introduce you tools and say it didn't show it doesn't show inside the final result even into the emulator when you run. It just for you when you design the app. It's for the programmeran designer. So you can see if you put 20 digits, for example, it takes this much inside your app. Anyway, we say if we want to access to button or other things, we first should find them. So we can say, I want to work with that object. How do we do that? We came to code and say, Just down here, you can do this. We find view by ID and give the type of object. For example, text input, edit text and from the reserves, from the IDs, you give the ID, and you have your object. We also said this has too much code. We can make our code lower our programs smaller, our codes lower. What should we do? We use binding and we defined this binding. As you remember, before we use this binding, we came and say inside this cradle down here, V binding equals true. We can use binding. Then we told you what is global variable and why should we use this global? And then on create, we give it the value. We also talk about null and null labor. We also say because our activity is activity main, we have this activity main binding. It's based on that name. For example, if it's logging, we have logging binding. And even if press control and in this activity main binding, click on it. We see our activity main because it is equal this activity may. We have this binding field with this data, and then we give our set content view this binding, because we want to connect this main activity with the view. What do I want from the binding that we just said it's filled b activity main. We want the root. We want the root of this binding to connect with our main activity. After that, we have this init listener. What does it do? This is a function that are all kl listeners. We put them all inside innit listener inside this function. We also introduce app. Also say why we put this question mark on this null able variable. If it's null, this apply part that contains the whole code until here doesn't run. We doesn't get any error. We won't have errors. Another good thing is we don't have to write binding PN ad. Binding question mark PN ad. We get rid of This part for the whole these BTN. Binding question mark dot. We don't repeat that here here. It's just really better. As a result, we directly can access to this BTN ad without any extra code. Then we say set on click listener. What is set on click Listener. It listens until you click on something. Then when you click on this button, it runs this code. For example, this is my button. I want to do something whenever somebody, click on it. So I say sit and click listener. Wait until somebody somebody click on that. Then I have this condition and this if I check is this inputs empty or not. Why? Because if these are empty, I can't add them. How can I add one number with empty thing? An empty thing, I can't do that with plus or minus or division. How can I divide a number on nothing, even not zero on nothing. I can't do that. I check are they empty. We also write a function for any poten that we want to do something. We give our first and second input for inputs, and we put the result inside ix result. For example, let me show you the sum number. We take first input and second input. They are ins, and add them together, then return them. What is the type of this function that returns. It's int. I have int for my output and my inputs. As I say, we put these results into tixy result into the property of this tixty result, property, have a name, what does it is text, and we have to make it string because this text just take string. If we want to give it number like this ins, it doesn't take it. Just a string. Since we confit this function and it's really good, We put in proper name and add them, we just copy this and paste it many times. Because we don't want to write it again. We just change this and the name, even not the whole name, the first part of the name. Why? Because I prefer to write less code, do more. Exactly because of that, we write functions to write less code, do more. We also learn a very good thing. This green check. If there is a problem, we can fix it. So we don't have any problem even we problems, and as a result, when all problems are fixed, we have this green check. So we are in a great condition. Before I forgot, we also have inside this resource, more than layout. We have these values. What does we have inside it? We have colors. We have diamonds, so we can give amount of spaces or other diamonds in this. For example, if we want to give margin, we give it inside these diamonds and then use it. If we want to change this eight to nine, we do this one time and everywhere somehow looks like our functions. We change one place and all the other places takes the effect. It's the same thing for colors. We change one color in one place and all the places that we use that color, change. We also have these strings. These are important as well. We have default string English, and we can't have other language default. My has default language of English because English people Or my targets. Or I live in an English country. But also Arabic people might use my apps. I add another language Arabic for my second language, or even it can be French. My second language can be French, can be Russian, can be Chinese. Why do I use Arabic? Because the English are left to right, and Arabic are right to left. The difference because they are difference. In the future, I can teach you a little more with this left to right and right to left. I even consider that. And everywhere, every time I want to write anything, I use this even if I want to write this plus, I use SCR. So if I want to change this text, I change it here, everywhere I use this text change. I don't have to check everywhere to see. Okay, I write one letter wrong. Let's search all the app entire app to see. Okay, I write just a letter right or wrong. I give the translator in my company the whole text. So he or she checks is this wrong or right, and compare it to the English text. These very pro tip, very professional tips. Because of that, please. These first days are really important. You must learn these very carefully. If you don't understand some of them, repeat those videos. I provide as much as I can many examples so you can understand them well. Your learning is a very important thing. Simply because you chose me to teach you. Because of that, I'm responsible. I try to teach you well. I hope you learn these things well. One other thing, let me just show you this manifest. This is my manifest. This is my app identity. This is what my app is. For example, what is my app icon? Even my team, what is my team? What is my target API? All important data like identity card that you have is in here. I won't explain this anymore. And you know each activity you have, you have one activity in here, and other datas are here. In the next video, we have a small quiz, and we wrap it up this day. 44. Day 5: Day5Quiz: Page five, quiz questions. How do I enable view binding? Question one. How do I enable view binding? Question two. What is a global variable? If it's too quick for you, you can pause the video, then write your answer. Into the next video, you check your answers anyway. What is a global varia? Question three, How to take input from user in function. How to take input from user in function. Into the next video, you can check the answers. Thank you. 45. Day 6: Day5QuizAnswers: Day five quiz answers. Question one, how do I enable view binding? You see, you just go to this build grade C T S. No that ends with project. That one with module, and inside that, you add built pictures inside that you add view binding equals true just like that. Question two, what is a global variable? Is variables that are created outside of a function. Why? Because we can access to these variables from any function inside that class. We even have variables that can access from other classes as well. We reach to them. I think through future courses, maybe After their 20 or 30, we reach that kind of variables. Question three, how to take input from user in function. Just like that first input. Second input, the type is in, the type is in, and the output, just like this, the output is in, and we return output, just like this, step four, First input plus, second input. This is our output. 46. Day 6: Decimal value: Decimal value. Welcome back. This is our last day of very basic level. Let's run the up. Hi this. We put 83 and plus eight plus three equals 11 minus eight minus three equals five, and multiply eight, multiply three equals 24. H that division press two, but two multiply three equal six. I don't have the decimal part. You see, if I enter seven, I s have two, I just start this app and now I stop this app. Minimize this. My code is in here. I have these four functions, for some four minus for division and for multiply. In division, I have two number, first input, second input. They are integer, and my output is integer as well. I divide them to each other and my result is integer as well as we can see. So I don't have any decimal points. And I don't have any decimal number in my results. We explain different type of variables. For example, R A is a string, it's a string. It's text, R p equals integer. Like one, two, three, it can store numbers. And of course, R, C, what is it a It can be true or false. Even we return ban in one of our functions, you can see. What else I also have variable d equals ft and variable equals double. These two are decimals? It can have, for example, 2.5, 3.5, 3.6, you can sort decimal numbers in the Let's give them some values for a string. I pressed equals. I press shift and the button next to the inter to write this character and Androuo, write the other one for closing for me. I just write a BC or number or the name. This is a string. The number. I can give it two or 23 or 234. This is the integer. B. I can give this true or false. I give it True. When do we use ban? When we want to say something is yes or no to force. When should we say yes or no to force, for example, in our function, you see, we want to say is not empty, yes or no. We use ban. How about fellow, we can give it Decimal lumber, for example, 3.40. It gives me error because if you want to give, decimal lumber to a fat variable, you should put a F at the end. Just remember. Okay, what else I have double? Let's give this number as well. 3.14 F. It gives me error. Y? Because I should not put an F. Put a F at the end of a double number. Remove it. It's okay. But at the end of a load number, I Put F. I hope you understand all of this. Very well. Let's just close it again, shift and the bottom on the up of inter. It's sort our code for us. Let me just check what happened if I say 0.2 I can't put a decimal lumber into a in. It gives me error, so I remove it. One more thing. You have a string in here. You can write one, two, three, four. You write number, but it's string. If you write AAA, it's okay. Why? Because it's string? Now, if I press inter and say A to int. It's okay. I can make my A to an int. Y, because I put integer inside this. One more thing, we can say one, two, three, four, five, 67890 Again, one to what happened. It says, your number is too big. You can't put this much number inside integer. There's another variable we talk about in the future lessons. But for now, we use int and you just should know, there's a limitation that you can put number inside any data inside, any variable. For example, let's kill these these. You see ten digits. If you put ten digits inside and in, it's okay. And of course, I think about 2 billion. No, no. Even this, you can't less than this. I think in the slides in previous lessons, we talk about the limitation, exact limitation. But as you can see, if you deal is one of these and even you put nine. For a start, it's okay, so I should understand if I want to use it, I should maximum, for example, maximum 999 million is my maximum number I can put in this for more, it's better to use bigger variable. Of course, it can a sore 1 billion or more, but it's better to not use it in that much number. And try to not break the limitations. We're not talking about long instead of in in the future, we talk about it, but not for now, those type of variables for the future. One more thing, if I write inside this string, A B C, but I say dot to ind, I have error or y because it's not a number. I should be careful. What do I want cast to what? I should just convert my number into number from that string or anything else. Let me try one more thing. Can I give this float? For example, just number three, an integer? No, I cannot. I should give it. Float. Let me just comment this, comment this. Comment all of these. So when you see the source, you can check them out. Anyway, I don't want int. Do you remember our problem? I want float. I want flow for my output. I have error. What just happened? It said you have d, you have in, you divide in to end, and the result is in. You can't have belod as a result. This is our error. Okay, k. Let me check it. You can't convert to in when they are divided to each other to a fellow so let me do this Dt Two flowed. Now, if one of the numbers is followed, it's okay. Our result is followed. Of course, you see, the problem is solved, but just to be sure I can write two flow. But even one of them is. Let's run the up. I'm waiting. Now, what do I have? Eight T division, two point D six and seven. Cutlin round the last number up y because this six is closer to 10220. Because of that makes the seven from the next number to seven, not five. This calls round up. Of course, since we're at level very beginner, I shouldn't tell this. Okay, let's just skip this thing. Anyway, we have our decimal result. Let me check another thing. 52 and sion 2.5, simply L et me just check one thing. I have eight, two, three, and division, I have this one, two, three, four, five, six, seven number after the dot. Seven number after the dot. Stop. So I have common seven number after the dot. Now, I want to check, how about double? Because I want to see what's the difference between float and double. I select this. I write double, and of course, to flood two double. Even if one of them is double, It's okay. It gives you double. But I want to be sure and to double two double double and output is double. Just remember, if you have two fd, you can't have output as a double because of that, I put one of them at least double. Anyway, we put for both of them double. Anyway, let's run the ap. I'm waiting. It's running mount, and if I say five, and I say two division, I still have 2.5, no difference. But if I say 83, and division, I see the difference, Let me look at this very closer. Let's count one, two, three, four, five, 67. Okay, eight, nine, ten, 11, 12, 13, 14, 15, 16 16. Instead of seven number after that dot, I have 16 number. After that dot for D Simar. So double has more capacity, and it's more specific. So we need more specific and accurate results. We use double. But when we don't need that much accuracy, we can use fellow In our calculator, it's a really simple calculator. So we use fellow float to flow, to flow because we don't need that much accuracy. Of course. Okay. We have a few small things on the next video. Because we want to finish beginner level today. Maybe we have APK output and maybe close keyboard and some other things. And then we close beginner level and start beginner level. I try as much as I can to explain very small details in this level in a few first days. So you have basic and fundamental knowledge of program. So in the future and next day, you have as low as low as we can problem as little as we can problem and I have a good start for this programming journey. Thanks for your attention. We continue until the next video. 47. Day 6: Export Apk And Tips Part1: Export APK and tips part one. Welcome back. Let's have a few extra tips and learn some new ts. Until now, we use emulator press app, and we saw our app. But can we make an APK? Yes, of course, go to build menu. Build a Bundles AP case. You see this on the right. You have two options. I just press build AP case. This is build my APK. I'm waiting so it's finished. My APK build it successfully, and if I press on locate, I can see my APK location. Let's press on it. I just click on this and click on locate and I see This folder open debug folder. I have this APK file. Just remember, this way, I have a debug APK. It's not a release. What is a release we talk about release output in the future lessons. But for now, you can easily and without very complicated steps, have a APK and stud it on your phone. Just copy this on your phone and open it and press in a stud. You can use this APK. Of course, if you need, you should active permission to install debug APCs on your phone. It depends on your phone and your Android version. You phone Android version. You can find tutorials to do that on the Internet. So remember, It's not for, for example, play a store or other stores. It's just for debugging on your own phone. So how do we do this? We just click on menu, go to build menu. Build a bundles APKs, and we build an APK. If we have error, we fail to do that. But since we don't have any error, we can do this and have our file. We say we talk about release in the future, but just so you know, release for releasing your app on the stores, for example, Google Play Store. Let's run the app again. Press run and wait. If I click in here, I have this keyboard. One, two. If I click in here two, I have this keyboard as well. Let's press plus. This keyboard is a seal in here. This is a problem. You see the problem? I should press this check to close it. It's better to change these buttons. So if I press any of them, click on any of these buttons, my keyboard close close automatically. So I didn't see this. It's look like I just press this. If I press any of them, it should do just like this, close it. Let's just stop this up and minimize this. And I tell you about it. If you have any error, you can't pull it. Let me just show you that. For example, if I have one space in here, I have error in this line. You see red, red, red. I have err in here. Okay, so because I have err in here, I can't pill it. Where else I have the error. You see if I go up, I have error in here. This just I can have a preview you see my preview. If I go on red in here and I click, go back to here. Let's go up again. We have error in here. And we can have a preview on that and click in here, go back in here. And also, I have this main activity. It has red underline y because it has error. I have red underline in here, I have red under the problem. And even if I screw up, I have red error in here. It shows me where is the error. And even on this. Let me just open it. Red under line and red under line. This is red dir line. It just shows me, we have problem until I came here and see, Okay, we have a problem in here. And let me just go to build build up bundle AP case, and I have error. But what happens if I press build AP case? Wait. You have exception. There on this file, line 65, if I click on it, I have error in line 65. I just take me to the error. So if I remove this extra space, it's okay. Everything is now just fine. Okay. Let's press inter in here. Just in here. Let's create function with no input. Hide hide what? K. K. Let's open and close and no input. Just inter. This is our function. Get this system service inter. It needs an input. Context, of course, context with big C. If you write a small C, you can't have that context. Because we are in very beginner level. I insist that every time. You should now I think understand it very well. Do you see capital. I shouldn't write. I should write. Write Big input input method service. And at the end of that shift and zero, and I press home shift and nine. I add two parentheses, and I just press one batch. Okay, I'm here as we are at very beginner level, but this is not very beginner level. You don't mind what do we write? Just write it. Input method manage dot We want to hide K hight so input from window. And I just say binding e mark and root dot window token. Ke second parameter zero, and another mark. I forgot that. Let me just minimize this height this and you can see the code. I press inter in here, so you can easily see my code. So we write our code to close the keyboard. Our soft keyboard, of course, Let me just explain more. I don't want to explain this code. It's okay. You don't have to understand it in very beginner level. But just let me explain some things. For example, let me just forget about it. You have set click listener. You don't have to know all the things on the background. Andrew D Studio and Catlin do for set and click listener. It's okay. You don't have to know. You just click Listener on your button. Andrew Sudio and Catlin language, do it for you. You just should do your code inside that and then user click on it, this code runs Easy Z, just like that. This is Catlin and Andrew Sudio method function. What is this method and function? This is predefined function. What I explain. For example, do you see you create this function? And one line of code. No matter and it doesn't concern anyone, any user. What do you do inside? Imagine another user. Want to use your function. That user only call this function. Send you two numbers and take one number back, and this number is some of this and this. We understand it very well. That user shouldn't know, shouldn't care about what do you do inside? What do you do inside the other one? What do you do inside the other one? This method gives me division which decimal point. User not know and should not care Just like that, we don't know, and we shouldn't know what happened on set click listener. We just should know when someone click Set click listener, run. And then we can run our code. Same as this. We just write another codes that are predefined on this Android, the Studio and cut language, So we hi keyboard on our program. But we should not know all specific things. What does it work? How does it work? Of course, in the future methods, we know Much, much more, but for now, don't worry. We write this code and read the studio, do it for us and cut the language. Of course. One more thing, I call this. I put binding inside this, and I write my binding variable. Why? Because I write my variable with binding name. You see, I declare this variable as binding. If I call it anything else, and if you call it anything else, you should write it another thing. The thing that you call binding is the name that we just called. Don't think is a fixed thing. No, we write binding for our variable because of that, we call binding in here. Even this, we call binding in here because our first variable that we defined has the name binding. If we call it anything else, in here it's changed as well. But this part apply is fixed. For example. Another example, this part is fixed, but this binding isn't fixed. This part is fixed. This binding, no, of course, root and window token are fixed. Just this binding is the name that you call. As I say, I just press control to see where does this thing goes? You see line 2227 and lots of code and comments. I should not know these codes and the other things, and how does these things do. Oh, my God, too much codes. No. I just use this input method manager. I use this input method manager. This part. And in the future, we know some of these, only some of these, only the parts that we shod know. Because we can't We really cannot read all of the codes. Even I I write Android programs. More than ten years. Of course. I think my first program is about 11 years ago. But ten years or more than ten years. So should I know all of these codes? No, I can't. There are, thousands of codes in different methods, and no, no, no, I can't. So do you don't worry. Please don't worry. So let's just copy this until here, control C, Then what then go after every set and click listener. Inter Control. Inter Control Inter Control. I really don't like to write all the codes. So I just copy in Control. I suggest you do this as well joy and do your job smart, not hard. Because of that, exactly because of that, we create function. So we do a smart, not hard, we write once. We use many times from that code. Let's run our app. Minimize this write 11 and 22, and press plus. What just happened? Let me show you again. Click in here, press minus, click in here, division. Click in here, multiply our soft key keyboard, virtual keyboard in here, heights. As I say, what does each part of the code do? We should not know. Okay, I know we use system service and other things. But we should not get confused in the start. Because it's not a complicated code, just hide your soft input from window. But we learn this in the future and many other things. We might just say, Okay, please use this code. Another example simple example, this apply. Do you know what does this part do? It has many codes inside to do your thing. But We just use it to make our life easier. We use it even here to make our life easier to make our code the and one more thing, the binding to do the binding has lots of code, but we should not know the specific things that behind the scene does. This is the I think basic thing that you should know about the functions. We write these things, so the user or ourselves when we want to use them, we don't care about the inside. We just use the function. And then we have error, as I say, we fix the inside. And after that, we don't care about the code. We just use the function. For example, we come and say to followed. After that, we don't care about the code. We just use the division. Okay, I think it's enough for this C D. We continue in the next into the next part and learn a few more things to wrap it up very beginner level. Thank you a lot. 48. Day 6: Export Apk And Tips Part2: X port APK and tips part two. Okay, welcome back. Where were we? We're looking at our project to see do we have any extra ting to learn before closing where we began a level? We just export an APK in previous video. Now, let's continue. First thing first. Let's look at that yellow warning. We have one week warning. What does it say? It says function high keyboard could be private. Where is it? I double click on it. It's on line 76. It's in here. So I want to do it. Make high keyboard. Private. Just like that on the right as we can see, private function, click, and I have this private function. Now, no problem in main activity. I hide this and I have this green check. It's really better. Next tip, when we just install our Android studio, we have welcome project. But how about now? We don't have that anymore. But we can create new project by using file menu from the main menu. I just press main menu. I have this file menu. New what new project. Because I want to create a new project, I just click on it. I have all of the template. Let's just look at them to see what do we have. But first, let me just close these and look at the open. If I click open, I can open my aller projects. You see at the moment, I'm in Day six, and this is my project holder. This is my project, my calculator. You see this green android icon because it's a project and I can open it. I just select this and click Okay, and my project will be opened. Okay, Let's just cancel this and go back to new project. Let's look at the left side. I have phone and tablet. I also have OS. It's for the watch Android watches that people wear with very small screen. You see, just like that, a small screen. And I can create a new app with select one of these. And it just does a few first things for my app. I can create empiba App or emptier a bit Ty and the other thing. And I also have this television. What is this television? It's for TVs that has Android. I can create for TV that has Android. And run on that TV. It also has t activity or with views and other things. And even the other things, we don't do things with these. Let's just back to phone and tablet. And from the Internet, you can download other templates as well. But let's go back to phone and tablet. You have no activity without anything or empty activity and empty and simple activity. So as we understand, these are all some pre return activities. These projects is good for helping us start. Soon. Now activity is empty. The empty activity, as you can see, the icon is the different way. We don't talk about that now. Basic view activities create, as you can see these basic tools for us as well. So we have simple menu, simple button. The next one gives us a few taps that we can switch between these tabs. The next one just gives us empty activity. Simple as we just create. Can see this one as menu, for example, you can put profile and other thing on the top and create game activity with Cips plus neative Cip plus. I think it's enough just talk about all of this. Of course, it's obvious, responsive view. Creates view that responsive for you. Responsive is the kind of thing that when your screen becomes bigger or smaller, change size. We have this on the web as well. If you forgot what what and which one of them do what you just can simply look at the pictures. It's really easy. For example, this picture has nothing and under that says you, what does it do? And For a sort, we just elect no activity. None of these categories and none of the semplate, no activity. I don't need anything. I just created from zero. Next. In the next page, we have name. For example, we say calculator for our project. We have this package name. And as we say, it's a unique postal code, you can consider for a house. If you have a house, it has a unique postal code, and in package name, you have a unique name like domain for sites for your app. People can make a difference between your app and the other app. This is very helpful when you want to put your app inside Google play. It's usually three part as you can see, or it can be four part. Like this, but it has a few roots. For example, if I just clean. I said, the package must have at least one dot separator. And if I put dot says package segments must be of non zero length because your second section has nothing. Okay, I say A. The error is gone, but it's not a good package ne. It's better to have for example.com and your side name. Follow that. For example, I have 70 20 four.com, and it says a digit cannot be the first character in a package statement, So I can not start with the seven. I say site. After that, this is my site 724 le.com. And after that, I say, so what should I do now? I say do my application name, for example, calculator, for example, news. Maybe I have a news app. I put news. So it's for this side and this app, and it can be a unique app and unique package name because I use my own site and my app name inside this package name. Also, you see, if I press space, you can't use this space inside this name. Has a few simple rules and tells you what you what you can and can't do. How about if I put, for example, B W for this news. Is it okay? It gives me no error, but it's most common. It is very more common to don't do this. I always even if the Andre studio doesn't give me any error, I always use a small letter and dots just like this my site and my app name. I never use For example, special characters. You see? It's not allowed. Simple ame, simple site, and these separated dots that separates your name. Anyway, save your location, where do you want to save this app. So as I just showed you, you can open your app later. What is your language? Okay, I use Cut. I can use Job But Google recommend cutling, and it's more powerful easier. I think it's better. It's my own idea. You can use Java, but most of the time use Cutling. I think in this year and the last year, I don't use Java even once. Most of the time cutling. But it's still there and if you need it, you can use it. From my experience, if you have 100 lines of codes with Java, if you want to do the same thing with cutline, you have about ten to 20 or maybe 30% less code. As you remember, we say, smaller a, I mean, ranged code function and lower code. It's better because you can fix the error more easy. We put minimum etc on Android seven. You can choose lower, but I don't recommend it. You see, I have even 4.1. Since we have maximum 14, I put minimum seven and when we have maximum 15, I put minimum eight. Why? Because You see that operating system. Grows Android operating system goes for the next level. It gets very new features. And when you select very low android, for example, if I chose 4.1, my debugging, my error solving became too complicated. I think I get so much error and nobody almost nobody or a very little people has this Androids. You see? Just now I put this Android 790 6% 0.5 of devices will run my app. Why? Because the rest of the people have those lower android. It's just a small percent, but my debugging, my error handling, my development became much easier. So I will not recommend to build up for outdated Android. About seven version of recent Android is good. I think it's default. When I open Android studio, it's default Android seven. I think next year, it becomes Android eight by default. Why? Because it's recommended, just leave the very, very old versions behind. Believe the last one recommended, I'm not going to change it. And when I press finish, it creates my a. Okay. Just cancel it. And in the nexto, we continue to see what else can we review and what points did we miss? So we learned them as well. 49. Day 6: Export Apk And Tips Part3: Export APK and Tips part three. Okay, welcome back. Part three, four, some other tips. Before I start, look, if you press new project, and for example, this one, looking for STCs available for download. Because we are not connected to the Internet in previous session, you see there's right for you. This might be old. You should connect to Internet to check it out. But when you connect to the Internet, you don't see that anymore. And just checking for anything changed. And after that, you have this like this. I just check it out my previous video and see because I not connected to the Internet, you see that message. Anyway, cancer, and of course, stable and good Internet connection. You need that. Another point, For building your project, you need some files from Android Sudio servers from Google servers. And if you don't have a good Internet connection, you you don't have them. You might not have them and then you have error. You have error for no reason. Exactly, because of that, you should check it out. First of all the other thing, you have Internet connection and you have the necessary file. If some of the files are downloaded completely or broken or any other thing, you can invalidate your cache and clear your cache and download them again. And you should also check these three optional things. So even Andrew the Sudo, do this very cleaner, very deeper, and better. Even you clear your local history fil system cache. You can check all these three. Of course, if you have crash for nos then error for no reson and you have a Internet connection. Now, you can do this if Klose and open android studio isn't enough. Anyway, I just canceled it. Okay, I just open this project. And you see this green check. This green check means it's okay. So I don't have a problem because if I have error, as I say, I should fix it. And of course, my classes have this check. We almost review all of these things. I don't think much of these things need to be reviewed. For example, we even talk about the three dots options and three appearance, Compact medial package and click on it and you see part by part your package name like this. These three dots, three appearance, compact medial package. Change this. Since we talk about all of these themes. Let me just think what else do we forgot to say for our ending up very beginner level. One more thing, I mentioned, if I come and click new activity empty V activity, I just got an error. Sometimes Andre Sudo have errors. You can report it. So Andre Sudo team fix it. I just press the report er. What is the problem? If I right click on this follar and new and activity, empty V activity. Nothing happens or just give me an error. Why? It can be Android Studio. Error? It can be my problem or anything else. I don't know. Since we are at very beginner level. We think what should I do? We just check it out. Android test. What is this? Just double recon it. We didn't create it. So where is our main at our main activity in here. You see, we didn't know what just happened. So without going to any detail, we just click in here, right click and in here we create our MTV activity. I just think maybe these things happens to you. It can be Andrew studio bog, and it can be your fault. In gar level, don't worry about. An Just learn and learn. Anyway, click. We have this. I just mentioned another thing. You can choose your source language. Our language is cul but you might want to create some of your activities with Jo. It's okay. You can have your co, your project, entirely with Katlyn, or entirely with Java. Or with both some pages, with Katlyn, some pages with Java, it is okay. It's another tip. And you might work with a team. One of your team members want to work with Java. One of them with Katlyn, I think it's not recommended I don't like to do that, but. It's okay. Or one more example, you find codes with Java language on the Internet and you want to use them inside your project. It's okay because And studio support both of them, some of your classes that you copied or take from another project or from Internet or from your colleagues can be Java and your own code can be Cut It's okay. I just cancel this. One more tip, we run our app inside our virtual voice. We have another options. For example, we can connect our own phone with USP cable or Wi Fi to our computer and do you remember that debug APK that we create Android studio create that kind of APK and send it to your phone and run it. And you can see what happens if, for example, an error occurs on your phone. And I think it's really better because instead of emulator inside Android, you have it on real device, but we don't check these kind of things in very beginning level. I just you to know that you can run all of your test on your real phone. Or even multiple phone, not just one phone. You have maybe one, two, three phone with Android 11121314, and you want to check on all of four phones to see if anything goes wrong or not. One important tip. I recommend if you want to test on a phone, you find phones that has highest selling number. For your tests. For example, see the market in your country if you want to release locally or entire countries to see what kind of phone and which model has more cells and you buy that phone. So you can test on the most devices just like that. I do this, and I recommend it, but you can choose another way. And you even can do this with two or three phone? For example, find three more selling phone and test your app on those three? Or for example, one of them be a bigger screen tablet, 12 or 13 inch, and two of them be regular phones. Let me check one more thing. I see. We talk about gradio Yes, I think we talk about it, but do we see version No, we did not. We can change our app version in here. For example, our version is two. You see pla if you check, you have one app is version, for example. 20. Next version is 21. Next version is 21.5. And so on you can change versions in here, and you can name them as well. For example, my version name is 1.0, 1.1, and my version becomes two or as I say, my virgin name is 10.0, and my virgin code is, for example, 20. And my next version is 21, but I just make a little difference. 10.1. First number is for pig changes. We don't change that a lot. For small changes, we change the number after that. For example, one or became two. I think we should specify video ten or 20 minutes just for how can we add our versions. Just be careful. I just mentioned it so I'll be sure you understand it well. Version code is an integer. What you can't put point on this. It gives you er. It's an integer. 21, after that, what just happened? 21.1? No, 22. Virgin code is for you. Virgin name is the name that you show to your user. So I just change it and it's a string. You see, this, and this, it's a string. So simply you can say, Okay, it's 0.1 now. But if you say 0.1 error, don't do that. And also SDKs and mine SCs and other things we have, we don't talk about them. Just this two. Remember one more time. This is integer 201-20-2203, and no dot. This is a string and virgin name is what that you chose to use. Pesto, you see that virgin. This is the string that you see in peleas. As you remember, when we change anything, we should s. Why? Let me just minimize this Because gradle files have changed since last project. So it's better you sync your project every time you change, and we don't change gradle too much. This is important file. Be careful. Since as I say, you beginner very beginner level, please don't change the things that you don't know what are those. For now, stick to these things I just said, but not too much. For example, you can't just change it 1-2. It's ok, change it to two and the version 1.2 became 1.1. It's okay. Okay. Let's just press thing now waiting. You see if I click on this, it shows me this background task. Okay. So it's finished successfully. Let me just close it and open and activity main to see what do we have in our activity main? I have this design view. I can see my activity as near as can to the user view. And I also have this split, and I also have this code. Let me just check them. Split. I have my code and my view design mode. Code and design. Now, code just code again, spilt code and design and design just design. Do you see this palette? We have some categories, common the most common objects, text, ben, rigid layouts. Do you remember? We linear layout, WordCd, we linear layout, horizontal containers, helpers, Google, Map view event, and the others. So let me see butten. We add boten. Of course, we use material, but Simply, if we're on design, and we want to add button, we can grab this, take it, take it, take it, release it. We have our button. And since we are in constraint layout, what should we do? You see the error open this error. Long story short, it says, you should connect this to soware. For example, to here. And connect this in here. For example, these two here, error is gone. Why? Because in? Constraint layout, you should specify how my object will be shown on the other side, of course. You see two side, I have to connect two side to remove my error. But it's optional. I add my third side. I even can connect this to here to here or even to here. This related to this as I connected to them. And if I look at the split, my object is in here. Constraint bottom to top half constraint n to end of start to start off. If I remove one of them, for example, this That line is gone now. The other three, as you can see, one, two, three, the other three will remains. So even I have this yellow under line, let me just press control z to have my four lines that are connected. Okay. What does it say? I say, please put this string, the button string into string resource because it's better. In the future in the future courses, we try to lower these kind of warnings as much as we can. But for now, don't worry about this as well. As you remember, I recommend that you write these codes as much as you can. Of course, you can go to design mode and see these to understand what do you have and what's their name. And even add them. When you add them, you can see the code. But I think it's better. I recommend it's better to write the code for each object. I know it's easier to use design. Because I just drag and up. But I believe it's better that you practice to use as much as you can the code. This is my recommend. One more thing as I see this code view, I think I didn't mention. This is with ema language. We write the full view with Mel language. Exemal language have this eMel at the first. I just want you to know. This is ema language, and the whole structure of our view is on emer language. Back to the button, There is our button. This is our button and view. What else do we have? We have attributes as well. You see in here attributes. Attribute for what, for this button. As you remember, we just write code. Why? Because it's better. But if we don't remember or just want to learn some of these things, we can in attribute and use some of that. And then write them in code. For example, I want these to be a little down, down, down like here, 89 90%, for example. You see my hands are shaking. I can't put in 90. It's 87%. Why? Because it's small and For example, my hand is shaking. And the other 144 horizontal and, let me just go to split. I have 87%. In vertical, 87%, I have it. Change it to 90. My hand isn't shake in here. You see? Why? Because this is really a small place I move my hand. But in here, I just don't have that kind of problem, because I write. If I can't reach teams and I want to be more specific, more professional, I use this code. But for a start in the beginning, as I say, it's came here and say, Okay, put it on the right, 100%. If I want 99%, I can go here and I say 1.0, no, 0.99, 99%. Go back, I have 99%. As you can see, I have this common at tribute. At the beginning, and I have all attributes. Most common at the top. Common. Later on, these and all attributes down here. You see? If I click on it, I have all of these attributes. If I want to find something, I came here, find it. But most of the time I try to use code. I hope I doesn't explain too because I just want you to know how important is to write with code. Okay, let's close the video, but just one more thing. Let me just because I open this. I just show you if I go to split, I can just take it in here and right click or open attribute. I have this margin that moves it, and I just can open this and remove it. I I type anything wrong, And also, if we just go up. You see, I just connect this to here and I can press in this x pattern or just remove it in code or press this x, just removed. So we can D this but left Android doesn't connect anywhere. We have this error. I can't move it up and down. You see, I can't move it to left Android. Why? Even If we connect this in here, I can move it left and right, because I should first connect the left side to somewhere, then because my left and right connected to somewhere, I can move it. I mentioned this because if you came and see you don't have those buttons, don't worry this button. You see, I select it, but I can't select it in there. I just came to code to have access to my button. I click it, click, click, click, lick, click, click. I can access it. Why? Because in design view, sometimes these kind of things happen. If you have the same problem, click, click, click, you can't have it. So simply split or even code, click on it. Now you select it because you're on that button. Now, came back to design. You have this in here and you can change it because you now select it. Sometimes even Andrew the studio have bog and because of that, you can simply do anything you want in code. It's most of the time better than design. But in design, as you can see, I have manyth, and I can change these things simply and fast and see what just happened in the second. So, we should combine these two things. But most of the time I go to code. Thank you, and I see you in next video. 50. Day 6: Export Apk And Tips Part4: Export APK and tips part four. Where we we. We just show you the design mode and we talk about these objects. Do we have anything else? Yes, of course. You see here component, come here and click on this. What do you have in here? You have your constraint layout. Under that, each of your objects. If you click on any of them, you selected. Inner layout, BTN ad, Bt BT BTN, TX V tX result and the button. What is this button? This button, the last button that we add. So we have them like a tree. Why? What does that mean by tree? It means since this DTI first value is inside that input layout first, it's a little to their right. You see, and if we close this, We don't see that or linear layout. Inside this linear layout, we have four buttons. These four buttons, if Kels it, T view is like this and open it Kelst pen it. Let me show you, project, you have these three view, Kels open, Klos open. Just like that, you have these three view as well, Kels open. Okay, What's next? We have some things up on this place. Let me just minimize this and minimize this and what do we have in here? I have device for preview, which device do you want? You can't have your preview on TV. You can have your preview on watches, Smartwatches, and the other you see Even cars, what else I have? This button? What does it say? System I mode? Let me just press on it. What do I have? Not night. Not night means normal view. Most of the phones are on normal view. But sometimes your phone is on night view. On night view, you have darker colors. So your eyes get be more comfortable. Let me just show you night view. In night view, your app is look like this. So you can check it out. Can you see things on night view? Can you read numbers, read the buttons on night view. Is everything okay on night view? Just remember, it's better to debug and check your app on night view as well. Let's back not night. What do we have orientation? What do we see is portrayed and we also have landscape. What is it? It's just look like you put your phone on the side. Of course, you can lock your app on the settings, so your app doesn't move on this side. Don't be like this. But if you want to be like this, you should divide it in this mode as well, but most of the time, I personally just lock it on this view. What else design. Surface, I have the design. But it also gives me forget about all of the other things. Let me just show you blueprint. This is blue print. You see, and I also can see design and blueprint at the same time. You see how helpful it is. But usually, I set it just on design, and sometimes I put it on blue design and blue print, and then I put it back on design. Do we have anything that we should check it out on very beginner level? Yes, for example, we can just look at these guidelines, click on it, vertical guideline. L et me just add one. I add this guideline, move it until here to check, is this with this with that are age or not. It helps me to see what object is there. Most of the time I use it for this. It has many other thing to do. But most of the time I use it for this. Maybe we talk about the other things that it can do, and of course, the others in the future, but for now, How can I remove it? This is the point. I I bring you here to say, How can I remove it now? I do whatever. Even if I close Andrew studio and come back. It's still here. Oh, no, what should we do? You just see go to a split or code. And see. This is an object. It's not a invisible line. It's really an object. So you just select it and delete it. It's a really important point. I think you beginner level might found it really helpful. Okay. What else you see this? This is really interesting as well. Click in here. Show all constraints. Look at the page and click on it. You see now we see these connections, what to what? If I check on check it and we have none of them. And also not love. We can check system UI. Yes, we can check system UI. If you check this system UI, you have this clog and battery and other thing on the top like real foam. It can be helpful. It's up to you. I usually just check it. Nothing really important in here. What else? And attribute, let me just show you one thing about attributes. You see, we just talk about these attributes. There's a lot of attributes in here, and there's a lot of menu in here. I can't talk about all of these things. But I just show you an example. Attributes, you have visibility. For example, look at this button. If you put this visibility and click on this drop down. You see you have three options. For example, if I say invisible, this isn't visible anymore. If I say visible, I see it. I I select this text and delete it by default, the visibility is visible. It came back to default, and I have so many other options and attributes. We talk about them in the future. And let me see anything else. We can just wrap it up to day and go to beginner level. Oh, one more thing. Let me just show you this as well. You see, we have this.it first value dot. What is this dot? This dot shows you the thing that has the property that has or the function that has inside an object or a variable or any other thing that you put this dot after. For example, this DT fverse value has a property of error or simple example, more simple example. We have this tx result dot text. So our tx results have a property named text, and also they have property name visibility, You see, you have all the other attributes in here. You see this, you see, text button, you change this text. You change this text. Let me just show you. Ck in here, press dot. Nothing shows control space. Finally, it shows. I have text I have error. I have functions like to string. I have hint and many, many things. I press V. I have visibility. I can change it in here. And of course, as you see, we have very many other things. Because of that, I press V. So it just shows me the things that have V and, as you can see, it shows me the things from the start first, one, two, three, four, five, six, seven, eight, T, that has at the first. Other things that have, for example, that has, for example, in the middle or after these and if I want to change visibility, I I should choose this and equals anything I want. Anywhere I want. For example, after an ease. If something happens, my button became invisible or another of my buttons became visible just like that. I think it's enough for very beginner level. Let's go to beginner level. We start with a project and we hope you enjoy it. I try to teach you as much as I can. Since I have teach this much experience, I hope I can teach you well and you learn a lot. Please, if you have any idea for making this course better, Give me a message and give me your ideas. These ideas, your comments, your reviews. All of these things are very, very valuable to me and has a lot of value for me. Thank you. Before I end this delete this and press delete on this because I want to put the source for you as well. Thank you. 51. Day 7: Game Intro: Game intro. We want to create a game like this. Just like our simple calculator that we do together and learn a lot of things, we want to do this together. So first, we want to plan our project. So what is my project description? And for example, how many pages does this project has and each page. What does each page has inside? And even what does each part in every page does? I should specify all of this. Then I can start. So let's start. My game has one page. This is my game page. This is my guessing number game. User in tres a number in here and a number in here in this box, and then tres a start. I also want this and this and this to be hidden. What does that mean? It means invisible doesn't show by default. The user can only see first and second box and the start. And of course, the report and the result. Just when the user press a start, this and this became visible. The user. Put number one inside here, number two inside here, press start and this shows and system inside here inside our coding, decide a number between this and this. Then these shows the user. Then the user, when this and this became visible. Inter the number. Press go a number between this and this that the user already enters entered. Since the system, our code, our program decide a number between this and this, when a user enters the number and press go system checks does this number is lower bigger or equal the number generated between this and this. Then the system tells into the result is the number equal is it bigger or lower? Is it equal UN. Anyway, I have report button as well. When I press this report button, the system shows all guesses that user make inside here and make it visible. For example, if I put inside here ten and in here 100 system, decide the number between them. For example, 50. And I say, Is it 70? The results say lower, I say 60. I say lower, I say 30, I say bigger. And if I say report, if I click and report, I can see What are my choices, my history of choices? History of guesses, sorry. This is my whole project, and we want to learn so many things by doing this. Our goal is not to finish our project as fast as we can. Our goal is learn as more as we can. Okay, I just press open, and since I want to open from the seven, I choose my project, and then press Okay. You see the green thing. It's because this is Android project. I'm waiting. My project builds successfully. If I go in here and you see this bill, click on it, it said Built successfully in 30 seconds. And of course, if my project needs anything, it downloads it as well. For example, any missing library or may be a library that needs update from the Internet. Minimize this, minimize this, and go to our code. As you can see, we are continued to make this project inside our calculator because in this way, we learn a few more things. How do we do that? We just inside this activity man add a button, just under these four buttons. And if the user click on that button, it takes us to the game page. So how do we do that? Let's open this project. Open this app. Careful. If this Android be on project, you might get confused. So it should be on Android. I have this cutlin plus Java. I open it. I open my package name. I have my main activity in here. This is my cutlin fight. First, just let me show you the button. I think we can learn a few point and tips in there. For example, I want to add my button, but I can't add it in my linear y. I just select one of them. I'm here. This is my linear. For example, if I just copy this control C and er in here, control, I have this extra plus and change the name at one at the end, so I don't have any error. You see, all of the five buttons, sit together in one line. Why? Because it's linear layout. If I add even five more buttons, it tries to put them in one line just like this. I don't want it. I want my button down here. And the big button, I want big button for entering my game. Let me just change this name to Ga. Now, I have BTN game. As I say, they can't be on top of each other and they are like a line. Linear layout is horizontal or vertical. If if it is vertical, they from here, go to down like a line. Even in that case, they are not on top of each other. Just like that, they sit side by side. So you can't add one extra button down here. It's a line. You can even have your parent layout linear layout. Just like this, I just copy this linear layout. You see this one constraint layout. If you just change it to. Linear layout. It gives you error, I have error. What is the error? You should say, what is your orientation? Vertical, horizontal. I just want to use this copy, horizontal or not vertical because we want to be upside from top to down vertical. Yes. We have this after that, this, this, after that, this on they're each other. And none of them in on top the other. Even when we say horizontal, you see they're out. Let me just put my mouse on here. You see on the right, they're out. Why? Because they can't be on top of each other. Anyway, just control Z, control Z. B, back, back. I change it back. Constraint layout. Okay, my BTN game. Okay. Let me just minimize this, minimize this and the others. I just minimize all of them and copy this button. I want this button. Control X. Because I want to put it outside of this linear layout. So, Then minimize this linear layout. Where should we put it in here. Or we can just go here. Another inter and control. You see it shows it to top left and gives you error because it says you didn't connect it to anywhere. These four circles are white. You should connect them to somewhere. This is constraint layout. You should connect these white circles at them at least two of them, one, de side, one de side at least. Why I just put it down here to show you. You see, it's here. If I just control x and put it here instead control. Is there any difference? No. Because there's no matter where you put this object here here or here. It's top left until you tell your object, where should be connected the object size. We should the object sides to be connected to it doesn't matter where and how is our orientation. It just shows everything that you don't specify where to show top left. But it doesn't in linear lay. You see in linear lay let me just show you This is our minus. This is our division. If I control X cut this division and control V, our division now is before our minus. And again, control x, put it back because in linear layout. First, you don't specify where these buttons are shown, they shown by their orientation. How you sort them. First object shows first first object, second object, third object, forth object. This is linear layout. But in constraint, doesn't matter. You should connect and specify how it showed. Oh, this is constraint layout. Let me just connect from view the upper circle to down of this linear layout. I still have my arrow. Why? Because I should specify left or right of my object as well. To be connected to what. So you see the code, just add my code layout constraint top to bottom off, linear layout. Let me just write the code for the next one. So start to start of a start of what ID linear layout. So my left is where the linear layout left is connected to that and my top is connected to the bottom of that linear layout. I click in here and I have no arrow. Why? Because I say my horizontal and my vertical at least one point in each of them connect to where. Press press press inter in here. Let me just say n to end to end of and press in linear layout as well, and remove this. You see, it's even faster. When you get used to typing, sometimes it even faster than you want to connect them in here and easier because I have more control and more specific. Now, simply STR ad, we change it to STR game. We don't have any STR game. What should we do? We can't press and inter or just this light bale, say, we want to create this string. We just copy all of this, and we just click in here. Create for Arabic as well. I simply write game and I press. Now I have my game button, as you can see, let me just this hand, you can move it by this hand with this button, um fit screen, and with this button 100%, and. Anyway, We just a little you mean, why? Because I want to show you with this hand, this is game, my game button. Now, where is it this string project, resources, values, strings, my English, default and Arabic string. English, this game Arabic. We can translate this Arabic as well. Let me just minimize this low this lose this and Zoom to fit screen. We have weight. This is for linear layout, but we're not in linear layout. We just copy all of these things. So remove this. So it's wrap content. What does wrap content mean? Means, take space as much as you need. As as you can see, it writes, the view should be only big enough to enclose its content. Of course, plus adding. This is my wrap content, just this size. This size. But what as we talk about? I say zero d p, takes from left to right. This zero dP works when we have constraint layout on as our parent. Layer, as we can see, we have constraint layout, so we can give zero DP. So we connect left and right. What if end to end of be removed? It doesn't work anymore. You have zero DP and it works only if left and right are connected, and the left control X doesn't work, only works then left and right are connected. Let me just show you in our text view. This is our text view, open this and we have zero DP and talk about it in here. If I say wrap content? It's too small, sticks to our data. If I say match parent, it's too big. It goes on our view. You see, it's on our text view. It's too big. How can I have perfect size zero d p. I have no interfere with my text view. I minimize this as well. Anyway, my button. Just one more thing, did I say the numbers? If I say, for example, instead of zero DP. 100 DP. You see fixed size, but not good. How about 200 DP two B 2202 B to a small 20 DP to a small. You see, I can't decide what should I do? But zero DP is perfect. Just for you know, you have this zero for it. But as I say, you should connect if you want to use for height, Top and bottom circle to somewhere, then you can use zero DP. And when you use zero DP, it means connect to the left and right. And for head, connect to the top and bottom. As you can see, I have mistake because this view is under this text view. Because of that, I just cut this and put it here. Because as we talk about, in constraint layout, it doesn't matter the order of these buttons, because these connect to each other by constraint start or end and the others. It's better I order these as I see them. For example, this before that, these and before that this. Of course, before them, my button. If not, I could be confused, we have our button. We want to write code, Because we want to do something when we click on our button. I go after PT and in here, press inter. I write Bt N. I have five button now, because I add TTN game. If I click on BTN game, what is click But set unclick listener and in here, just like this. Now, I can write my codes in here. I select wrong thing, but let me just show you. If you select the other unclick listener. For example, the first one, you simply remove the extra thing and add this. Why? Because we don't want to give this any parameter at the moment for this code. As you can see, you might have different set on click listener, because we can choose between them. Anyway, if you select the other one, simply, for example, this one, sorry, for example, this one, you simply remove this and add this. We shift and nine, and then if it doesn't add the closing part, shift and zero on your keyboard. And do you remember since we write this apply, we don't have to say binding que mark D PTN game and another question mark and the other. We easily write PTN game. Even, we don't have to write question marking here, simply easily. And also, I think you remember find view by ID that we should write many codes to find our object. But we don't want to write that in here as well. We just use our PTN name. So if you there, click on this button, I want to open our another page, another view. We do that in next video. So we don't make this video too long. Thank you. 52. Day 7: Game Page: Game page. As we talk about, we need a page like this, and in previous video, we just talk each part do what? Okay Let's continue. Open project. We have this in here. If you see this part by part, just click this option, click this options three appearance, compact middle packages, like this, or like this, like this, or like this. We keep it checked. So click, we have this in here. Right click in here, new what, new activity, what kind of activity? Empty views activity, see the pad or just move. Don't do anything with the others. Just go to activity. Okay, click empty view activity. We have this page that helps us create our new activity. What if I remove this number two and give this main activity, I said activity name must be unique. You already have this main activity. You can't have two main activity. Let's choose different name. For example, game activity. As you can see, I put upper case letter for start my each w. And as I already told if I press space, it gives me error, so no space. Since it already checks generate a layout file, and if true a layout file will be generated, O layout name comes based on our activity. And most of the time I leave it like this because it makes sense. Let me try that in here as well. Space gives me error, so no Space. Is it my default activity? I mean, if I run the app, this activity is the main activity, no, it's not. So I don't check this launcher activity. Of course, I'm not going to change my package name, and my language remains cutlin because we're going to teach cutlin in this course. What now you see this finish, press this finish. Now we have our new game activity, our new activity. What do we have in layout activity underlying game? Minimize this and we have it in here. Anyway, I just comment these lines. What do we want? We want to go in main activity on BTN game. And when we click on this BTN game, it takes us to our game activity that view called activity game ML. I write start activity. Start activity. It needs input. We talk about input in functions. So we should give this an input. What kind of input? It needs intent. So if you go on this and press control and press your left click, you see this. You have two kind of input in here. You can just put intent, and you also can put another thing after that intent. Anyway. I just say for more information. If you want to see how many options do you have? Go on that thing. Press control and click and see how many declaration do you have for this method. So, let's complete this command. Go here and write in ten application context, and just the button write to the M game activity class, Java don't remember. Don't forget that dot. Let me explain very simply. Pay attention, pay attention. With intent, I say, what do I want to do? This start activity can do many kind of things. But I want to say what I want to do. Long as story short intent helps me communicate between different components. In many ways in my program, and it does many different things, so I don't want to make it complicate. So let's just use this intent to navigate among different activities within our application. We want to know this kind of use of intent for now. Our first parameter takes context. Let's just not talk about the context and just select this and write this at sign main activity. Our main activity to go where game activity. Don't forget about this separator. It's just next to M. If I remove this Java control X, it gives me error not ok. If I remove Ks, it gives me error not ok. Just write like this. Even if you forgot about one of these, it gives you error. To write this, you should press shift and the button write to the, just like that. So, for example, these parts are fixed. If I have another page, for example, login activity, we want to go to for example, we have login activity. What should we write in here? Easily. You see this cutline? The name of our cutlin code, we write it in here. No activity underlying game, no, no, no. Our cutline fine. Our cutl file game activity game activity this part is fixed, but this is the name of our cutline file the second part and the first p and the first part, as we say, take a context from you. Application context. All activities has an application context. For example, our main activity, even our game activity and all the other activities that we might build has this. Let me hide this. They all have application context, all of them. That is my context. What is context? Don't worry about it for now. But if I want to make it as simple as I can. It's very beginner level and I try to be simple as I can. This application context has some data has some data inside from this application task, and even where does those tasks came from. And even the options, no the configurations of those tasks. So lots of these data for our application is in this application context. It's some kind of variable. Okay, let me just tell you, this is a variable that has some data inside. From our application task, and the information of those tasks. For example, configuration and history of those tasks. Yes, it's really better. Long story short, this application context is a variable. It has a set of data and this data for our tasks, and even our tasks, histories, let me just clean this. But as I say, you don't have to know just you should know that your intent, where is our intent here? Our intent needs a context. So we give this intent, our application context. Just like that, And remember, we have a lot of other things with this context. We use it many ways many times and many other places. So don't worry. We use a lot and you get familiar with this. For a star and for now. Any function that needs a context, it's easier because most of the time it's okay. We give it application context. You can write these things somewhere or simply we see lots of these things in future videos and you understand. Application context is for this activity. So we want to change it instead of say application context because we want to say, this activity, let me just say this at sign main activity. What is main activity? This is main activity. So I mean this activity, take this main activity. Take this activity, whatever these things name. This, main activity. And don't forget this at sign. At sin shift and number two on your keyboard at the same time, first press shift, then number two. Sorry if some of these things you already know, I just really, really want you to learn very well. This is really important. You should learn very well. Okay. So let me explain more. What does it say when when I write this? This means this. It's English word. This means this. This what? This, this thing, this thing I've just in. Okay, what do you want from this? I want main activity from this. So I mean this main activity. The exact words in English. From this main activity that I mean, I want to go to go where? I want to go to game activity. Here, game activity. You know why I explained this much because these kind of teams are the teams, my students ask in classes. Ask what do you mean by this? I mean simply from this activity, go to this activity. This is my activity that I'm already in. Let me review. That's a long video. We repeat this many times. We want to do something. We want start activity, and we say we have this intent to say what do we want to do? As we say, we use this intent to navigate between activities in same application. Okay, from what activity, this main activity to what activity to game activity, As we say, we can give this application context, and application context, give this exactly this. Because application context in this contains this. These are same thing. Don't get it wrong. Finally, we just write one line. Let's go and see what did we do, Rn Dia. Okay, my project is up, and this is my calculator and first number, second number, my game button. If I click on this game button, this BTN game set click listener runs. So I click in here. And I move to another page because I start activity. What activity from where to where? From where to where. Okay. Let me just call it from where to where from where to where from main activity to game activity. It's better. I shouldn't describe this. I can't these things for now with simple mes. Start another activity, go from where to where from main activity to game activity. Easy PZ. Okay? This is my new activity, my game activity, and of course, activity underlying game that XML. This is that. No cuting. You can't see that cutlin code. You can see this XML code. They are different. This is what you see. This is the things that program do for you when you do something. The reactions. Yes, let me call this cut lin code reactions or things that you want to do and react. Yes, reactions. Why not? Let me just press this back. You see this. And again, you see this. Okay, finish stop and minimize this. And let's go in here. Split this. Let's just continue this in the next video. I think this video became too long. Sorry for explaining too much. I tried to solve any question that you might have on your mind. Thank you. 53. Day 7: Arrange Game Page Objects: Arrange game page. It's now 0.4 create this page. We have all of these objects that we talk about in previous video. Now we want to create them. Previous video in activity main we click on game, and we came to this page. But this is empty. So how can we feel this? We need to input, first number, second number, so the user can input those numbers. We just go to activity main. We have this, and we have this as well. Let me just change the gravity from start to center. So they look like the same. Let me just copy this style as well from the second one in first one pasted and remove the extra empty lines. So And I just copy this style from the second one in there as well. So they look look like just the same. They're similar now. Now, I just close kilos, kilos, and let's just copy this. Control C, and in here, activity game inter control, and remove this comment that we just bring with us. I have these two edit text. I just copy this, but you can also type them. By because it's better for learning that you type and you give each of these properties. It's a good practice. Please type these things as much as you can. So you can learn what are these. As I told you, you should write them as much as you can. But For not waste time of teaching, I just select this button. This is my button and control C, control V, and of course, minimize this. Since I just copy, it gives me error, y because it doesn't have any linear layout in here. So what is this button? It's PTN start, and I also change the text to start. As you can see, I don't have any start. So press inter or press this light b, create a stream value for this resource. Check Arabic as well because I have two languages. What is our value? Start. I press. So of course, since I don't have linear layout, I should say This is my second input. I want this ID input layout second. I just copy that, but you can type it instead of this linear layer. This linear layer, I just paste it. Of course, top two bottom of what, I don't have linear layer, so input layout second. Even when you learn a lot, sometimes it's better to type, so you don't forget things. From the left, connect to the left of this, from the right, connect to right of these, and from the top, connect to bottom of this. You see after start button, we have a box as well. So we just copy this like this and go to the end in there and paste it there. Have error, what does it say? Our name is problem. Input layout, what should I call it? We intern number in here. Let's just say guess, because user guess the number, and of course, DT, Yes. Do you see this light pub? If I go in here, the light pub gone. Sometimes we have a few errors, but they might be Andrew Studio put. For example, if I click somewhere else, the errors will be gone. It happens. And it's okay. Each new version of Andrei Studio came and the bugs became less and less. And of course, I had this PTN start and where should it be end to end of my button, start to start of my button and top two top to top of my button. But as you can see, if I say top to top of my button, my text box and my button b to top of each other. Top of this equals to top of that button. So I think we should change it. Let me just say to bottom up. And if these kind of things happen, you can just select from here to here to remove extra part. So top of this object to bottom of the object, I just say top of this to bottom of this. Anything else, let me just say int? Oh, I just have hint. First number, no, no, no. Let me just change this as well. SC R. Your guess. So a so guess, I don't have a SRO guess. Let's just create it and in Arabic as well. Let's just write your guess. Well, let me just show you, we have the strings. Just check. Ast your guess game and Arabic game asst your guess. We have this. Klose that, Klose that, minimize this. What's next? We have this button, this report. Let's continue. So next is our button. This pattern, we just copy this and at the end of this. I just paste it. Of course, it's PTN. For example, go is a good name, I think, and text, it's not a start anymore. CR go. Now I don't have it, so let's just create it. Go and not forget to check this bic and. So it's on the top of the other button. We should it be? I have this input layout gas, control C, and change this toput layout guess to a stat of and to end of input layout gas and top to bottom of input layout gues. So my go button is now in here. And let me just show you if I write EDT guess, what happened? Control C, If I say EDT gas, it gives me error because I can't do that. I should control C, input layout guess. Because we don't have any EDT gas. We just have input layout guess for connecting these. See if I select EDT gears, it doesn't have that white circles. You see, but the other one has that circles. It can connect to connect to something, but this one cannot connect to anything. So long a storage short, our digest are inside another object. Because of that, we can't access it, and you can give your top to bottom of to end of and the other thing based on the things that are inside your constraint layout. Not on the other things. So I can give Input layout second. Because it inside our constraint layout. But if it's on the other thing like this DT second value, I can't do that anymore. Anyway, as I say, you can't see that error anymore, why? Because it takes time to go from there and you can click somewhere else and came back and you can see even it's not in the left anymore. Before the middle part, I remember we have the result on the bottom, and we also create the result in here. So let's just copy this. Minimize this, minimize this, and of course, this view this this and this. I just copy control C of this te. You please type as much as you can, but I'm not in here, so you don't waste control V. We have the in here now. Okay. What's left? This report and this button. Okay I here. Let's just type this one and the card view. I just write CA and I select this card view. Just check again. Android X card view Widgit card view. Okay. It's okay. I just select Match patent. It's on that by default, and of course, wrap content. It gives me error because it doesn't connect to anywhere. But first, I should close this. Okay. Shift and the button right to the M, and a slash that is next to shift on your down right the buttons of keyboard, left to the shift button, I just press it, and it writes the rest for me. I go start of this and inter inter. I close this. I just forgot. I don't close this. Shift and bigger. I writes that for me without any more thing, I should remove this and inher inter. So now top, not in here, but in here top to bottom of to bottom of B and go. Let me just do this again. I just write constraint top to bottom off. For that, I just write bottom off and it gives me the four. I press inter on the first one, press J, and I have BTN like this. And if I want to show you again, I don't remember that. You see? I I just want to show you again, how to write that to of I don't have it. Why I don't have that? Because I just write it. But if I don't write it, I can't find it. And G BT. Understand, if you write it already, you can't find it, it misleads you. You get confused because I want to show you and I can't find it, I got confused. Because in normal programming, I shouldn't write it many times. Start to start of what. For example, P parent. Press P and then patent, and of course, end to end of end to end of what parent again. Let's give it a margin as well. In here, margin, that sign g. Since we call it normal margin in here, I just should say normal margin. I just check the name. Give it normal margin. If you get different names in different projects, you might get confused like just I do. This is another tip as well. In card view, you can only put one child layer. So we just go in here. So I put a parent layer. Let me just show you. For example, I just write CO N, and the first one is constraint layout and match parent and rack content, and just close it as well and inter and click in here in inter mean height for example, 200 DP. I just give this card view card max elevation. And I just say I clear this and write enough ation, and I don't have it. So give it eight, if you forgot to put DP after that, you see, you just put eight. You came in here and put DP. This is a common message as well. Can minimize this, came back. Now it has eight DP. Now, just press inter and A, and give it radius. I just press inter and D. So I can give it i radius, I think, and it doesn't have it. And create this one as well. A. We don't forget to put DP. If we do, we go and put it in there. We have this ADP as well. You see my error isn't gone. But if I click in here and then it came again, my error isn't there. It's a simple bog. Don't worry about these kind of bogs. It's okay. Now, let's run our app. Okay, we run this in 7 seconds, hide this and press game button. We have this page. Let me zoom in. You see our first number, second number, our start button, your guess and Go button, and this carviw. I don't think you see clearly my car view. Let me just stop my app and minimize this to show you better. First, I should give a background at the top in here. For example, in here, I just say background Black. I think you see it better. We just say background, Black, so you can see my card view and just want to I just want to change this radio. So you can see what is it? Control X, what is better way to learn than see what just happened. For example, 50 DP, or even more. You see the corners, I give this more 90. You see our corner be like this. Let's put it back. Control we put it back. If we don't give it this Control X, it's very sharp on the corner in 90 degrees and pointy. Because of that, we just give it eight d p. Let's go and clear the background as well. Remove this back. Now you see our card view. We can use material card view. Like button and other things, it has more tools and options and possibilities. And Android Studio and Google itself brings that for us. So, I just write card view. And instead of that card view, I go down. And second one, I have material card view, as you can see, and Android studio itself, put this material card view closing part in here as well. It is really good and makes my work easy. Because if not, I should come down here and change it as well. As we already say, if we have material for the object, we try to use material for that object. But I just want to show you regular object as well. Anyway, card view as we told gives us a box, a place, this much, for example, You see, we need little space. For example, this much space for our report. Because of that, we add our card view. And we add material because it can be more beautiful and has more things. So I just go down. I have my text view taxis, yes. I just copy this text view. Control C and put it on my constraint layout inside my card view. Let me just open it. I want to say top to top of parent, of course, and of course, end to end of parent, and start to start off my parent, a little delete. And sory patent patent. That's right. Now, it's look like this. I don't want to use tools in here. I want to give this and tax. Because I don't want tools now. Because as we already talked about, tools is for me the programmer. Now, high the string, remove it, control space. I want to put a string. Name. No, Of course not. Of course not. I just press inter, so I have at sign string Slash and I remove this part and say STR underline report. But it doesn't recognize any SCR report. Let's create one and check as well, and report, and. Now, it says report, and of course, our IDs report labor. It's our name, our name of object. We can access to this object with this ID with this name. And not zero dP. Just trap content. It's okay. And one more thing, I need a button. This go button. Let me just copy this and take it here and change the name to BTN. Report, and of course, STR. Report. I want to say top to bottom up, but I need to give this an ID. You see? I don't have ID. So I can't give the other object this thing's address, this thing's name. So what should I do? ID? What is the ID? Of course, it's a card, so card. It's for report. So card report, and let's go down. In here, top to bottom off. What card report, constrain top to bottom off, Card report, and this zero DP rack content. O let me just have that zero DP. It's okay. I think it's enough for this video. We continue on next video. 54. Day 7: Other Changes In View: Other changes in view. Okay, what do we have? We want all of these things and also we want these three be hidden. Welcome back. Let's grab this a little down. We just go back to this material card view. We talk about this radio. I did this wrong. I shouldn't use Max elevation. I should use card just elevation. Why? Because I want my shadow. You see this shadow. I just click up there to unselected and you see the shadow. Because I write Mx elevation, I write that wrong and I don't get that shadow. Let's run the app. I just click the game button. Okay. And you see the shadow. Let me just zoom in more. You see the shadow, if you run write any other property, as well, you might not get the good result. This is another point. Let me just stop this up and go back to ding to see what if I give more than this eight. For example, control X, for example, 40. You see how much more shadow I have or 20 DP or ten DP. You can see the difference or even one DP. The shadow is gone, almost gone, ten DP. I put it down so I can show you. But you understand the point. Anyway, I just control re pat it back. You see most of the time I use some predefined number on my mind. For example, four, eight, 16, 24. For example, this is eight. If I want less, I put four. If I want more, I put 16. It's on my mind it's on my mind and it's my rule. You can set another rule. For example, you can say five, ten, and 20. It's on yours. But it's better to use the same number all around the project. As you can see, if I open this project and show you the diamonds. Even in this seven, put it 88888. If I want to give other things, I say 16 or four or 24, I say specific numbers. So all time other teams have almost the same range. For example, for a small, I put four, for big, I put a specific number. And for each project, sometimes I write it down this specific number. I know these are my range. And as you can see, most of the time is eight or four or 16. Let me just close it as well. Just for remind you, I just me one to one. This card view only takes one layer. Inside it, I put this constraint layout, so I can put many objects inside. For example, if I put one more object beside this constraint layout. For example, it takes. Let me just control C, control V. It's not okay. So since I should only put one object inside this card, you, I put this constraint layout and inside this constraint layout, I arrange my objects like this So anyway, let's continue. We have this text view. I came here and press inter just after this gravity, I say text text story. I have three different choice. See if I say italic, let me just mean so you can see this better in here. If I say this italic became like this a little to the right. If I say bold, it looked like this, became bold. And normal it's just normal. It's better you don't write because it's already normal. Anyway, I want bold So it looks a little stronger and bigger. So we make it a little bold, and also I want change the size. So I say text size. You see this text size? It is 14 dP by default. You see 14 d p by default. Let me just control X. Okay. You see, and then control V. I should just cut whole line. Control X. Control V. No difference. Why? Because it's default. You can say, for example, 20, it became bigger or 40 really bigger It's up to you how do you want to this look like what, as I say, if you give 14 is default. So if you want to be bigger, you should be more than 14. If you want to be smaller, you should put a number lower than 14. So as I say, I like to write 48 or 16. So I give if I want to change it, I give 16. It gives me a warning. What does it say? It says should use SP instead of DP for text sizes. Let me just change it to Sp. But what just happened? In Android phones, when you go to setting, you want to change the sizes. You can make them bigger or smaller. As you can see, many phones has this setting in Android. I think almost all of them. If you change this to SP, when use phone setting, change the phone text size, your app, this SP changes as well. For long story short, with SP, we go with font size adjustment and setting. For example, if we have 14 and we make it double, we have 14 by default, we make it double, for example, 28. It's become double of others. When you change the font size of the whole phone, your Sizes are relatively to the other texts in his or her phone became bigger or smaller. I hope you understand it well. I hope you know what I'm saying. And long story short, all the text sizes you use shod be SP, all of them. Of course, it's up to you. You can use DP, but it's better to use for all of them, SP. One more thing. We have this margin. Yes, it gets a lot from top. I don't like it. Just from the side. So I change it. I put one horizontal. Just like this. Let me just select it and see the right. Now I om it for you. See the right. I want to press control X, S the right. This is the difference. See the right, control. This is the difference. You see? Now, if I want the normal is like this, and if I want just from the side, it's like this. It's better, I think. I don't want too much space from the top. And only spaces from right hand left. Let me just run the up for you. I press this green round the button. So let me just see what just happened. Minimize this and zoom out. Go to game. Okay, I have this. It's good. It's pretty good. But one more mt. Do you see any problem in here? Do you remember this? I should hide this, this, and this? These are hidden. Let me just back to the code. As we see, we should hide this, this and this. But now we just saw them. They are not hidden. Now, let me just stop this up? And minimize this and oom out, of course, 100%. And your guess, I have this. Should I write any code in here inside this text input edit text? Of course not. You see this text input layout. This I click in here on text input layout. After this lend, I press in there. I say, Visibility. Just with these three words, visibility, I found visibility. Which one do you think? Let me explain this for you. Just as I say, you see how fast I write it even faster than you want to try to find it in attributes. Let me just check that again. I have visibility inter, just like that. This much faster. When you became familiar with different codes, I believe this is really most of the time faster then work with this design mode. And also, I have so much more control. Let me just see what is these three options. I have visible. Let me just select visible. What just happened? Nothing, absolutely, nothing because it's default. By default, my object is visible. So nothing happens. What else do I have? I have control space. Control X to cut them and control space to see other thing. I have invisible. And I have gone. I just want to see what is this gun. I know invisible, but what is this gun? My object is just gone. You see the space. There's no reserved space for that thing. It's gone. It's nothing done. But how about invisible? Let me just look at that as well. Control X, control space. And I have this invisible. You can guess. Yes, I have my space, but my object isn't here. You see how good is it? Control X. I have this. Control V. I don't have this, but the size isn't change. It reserved for my object, and then my object came back. The go button is still here. Why? Because the space reserved. Let me try it gone. So I want to do this for the button as well. So I just select this control C, go down. This is my button, and press inter control, and I just select this, delete this extra line. My button is gone as well. Of course, I have this card view in here. After the margin, I press inter for this card view and another control view. This is gone as well. Let me just run the app to see what just happened. Now, let me just minimize this and press game. You see, I don't have them anymore. It's good. Now, let me just stop this and, go back to our cramming part. Now, the problem. I make this visibility gone for the user. But also, I'm not seeing them. Of course, I still see them in code. This is the good of code view. And it's really hard to work with. Because as I say, I can't see them, and I can't understand how they are look like. I showed you extra tip in very beginner level. And if you forgot, I show you again so you understand the thems I just to you in previous sessions, they are base fundamental and very important thing. Let me just show you an example. I just press inter in here, and I just wait a second to see, do you know what should we write? Yes? Of course. Tools, tools, visibility. And what should we give to these tools. Of course, we give this visible. What just happened, what just happened. What we use these tools. We use these tools to see thing unchanged thing just for the programmer just for myself. Not even in emulator just for me. It's for nobody just for myself. So I can see this visible. But even if I run the app, and minimize this and click game. I don't have it. Why? Because tool is just for me. Do you remember Do you remember where do we use it? Hide this, and of course, stop it. These numbers just down. We use it to see how many numbers can we fit inside this result, and we just make it visible to see how b and how does our card view just look like. But when we start the ap, APK on user device or even in our simulator, In our emulator, we see this gone, and this visibility is just for this design view at the moment. So exactly because of that, I add visibility for tools Android for user tools, for me. I hope you understand it well. And you know we use all of those things in very basic view, lower basic. Many other places. Exactly because of that, I mentioned those things in there. Now, of course, in beginner level, we understand many other things and in the future, because these are also important. We use these as well. So learn these carefully. So let me just copy this to select this. Control see on your keyboard. And inter in here control V, and of course, not text input edit text, but text input layout. Inter and control V. I have all of my objects back, but just for now and for myself. I run this app one more time. You don't have to run this a as much as I do. I run this app because I care about you and like to show you what just happened. So I have these objects to see what just happened, and I don't have these objects in. Sorry in this page. Let's continue on next video. So we write some line of. Kathleen Cats 55. Day 8: Writing Primary Game Codes Part1: Writing primary game codes part one. This is our app that we want to create. Let's continue our app. We go to game activity C T, to write codes. First thing is user click on this start button, and then we check first number and second number is then empty. Let me just close this one and this one. So we have our two important things and change the orientation bar. Grab one, the other side or the side sorry or here. Just like this, you can arrange them. Here my view and here my code is I just press tab another tap to be here. And I write in it in it listeners and open and allows. I don't have this function. I just click on it. I and inter, create function or that light valve, do the same to do, I delete this to do. This is my function. But I just want to use binding that we already told in beginner level. So I just click here and press inter. I write binding. What kind of is this? Activity gain binding? Question mark is equal. Null. So I just write w binding. What is it? Activity gain binding? Why activity gain binding, activity game activity game because it's my view, not my cutlin. What should I do now? I see this has an error. What does it say? I say, I need the lass, I should import that class. What Klass? I should import this activity game binding lass. Okay. Do I have the in my main activity? I'm not sure. Let me check. I just go to main activity. Minimize this, go up up up. This import activity main binding. Activity main binding. Just like that, I have activity game binding. Just minimize this import and go here in here inter, I just want to separate this. Create, and before set content inter, I have this binding because I want to give this value is equal equals to what equals to activity, game binding. I just write the A dot inflate and give it layout inflator. If I say this line of code very simply, I think I could say we just to render to pause our layout So we inflate it because we want to parse it, we want to fell it into our binding. We want to feel this view into our binding variable, and because of that, we feel it inflate command. We want to create elements, create one element view element from our file that this method, this inflate method, do that. And we should give it some input. And we give this layout inflator. I hope I say this simple enough. And with this code, and of course, activity gain binding. It's a part of activity gain binding. We give this binding our view, this activity game view. Now, what should we do since we fill this binding, We now can use it. Because this binding now filled with our activity game, we can use this binding instead of our activity game. This resource layout activity game. This is exactly address of this activity game. You see, resource layout, resource layout activity game, exactly resource layout activity game. So minimize this. Now, we want to set our content view and instead of addressing like resource layout activity game because we feel this binding with the whole activity game that XML, we can use this binding instead of not just this, since it's filled with the whole view, we can use binding, and of course, our question mark, and of course route. Now, it's okay. Now, our binding route that is our layout file is in set content view, and our content that is this activity game connected to our game activity. I really hope I put this together simply. And what is this route? This is our root view. The top layer of the whole thing, et cetera, the whole of this. Let me just say it in this way. Root element is the top element, top of all the other thing. For example, even when we do web designing, if we want to say in web designing, what is root element? We say the top element, for example, in a HTML page, HTML tag is the toes element. So that is root. And in here in our binding, what is root? What is the most top thing? Of course, the whole page. The place that contains all of this XML is our root. I hope I say this one simply enough as well. I also should mention, we defined it globally. We talk about globally in previous videos because we want to access to this variable inside other places, not just here. Okay. Let's back to work to see, we understand all of this and we write this. Now, what should we do? We write binding dot sorry question question mark. Dot app. Don't forget about that question mark. So since the apply, we doesn't repeat that question mark. Let's continue. Now I write pn, PN, Pn start dot set set and click listener. If you suddenly write two parentheses, remove them and shift the button after P and in there. I have my C, set and click listener. Just remember if you forget about this and of course, binding, you don't have the TNS start. You should write this a binding that alo. Don't remember that. Now, I just mention it. Let me explain it more. Comment this again. I don't have PTN start. Let me just control a space. I don't have it. What should we do in this case? We should write binding question mark. Do PTNS start. Why? Because we should repeat that binding many times. And because we want to don't write this, we simply write this apply. And of course, even said, put a question mark. You see, instead of this question mark, and this binding, I simply write this apply anyway. I just have a fast with you. This null means nothing. We make this binding null label with this question mark. We put this question mark in here. If this binding B null. This apply part won't run, and we don't have any error. So we click on it. Long story short, we click on it. What should happen? We should go activity game. First number, second number. Are they empty or not? So let's write code, but we can do something better. Let me show you. Open this project, came to this main activity, came down down. In this main activity, you have this private function from here to here is not empty input. Control C, then what ellos this down here, when it listeners finish, inner, now, control V. I just copy paste it so you can see how easy can it be. But you can write it to better learn it. Let me just show you the code. This is the code you must write. But it's okay to copy paste when you know what does the code do? But from time to time, it's better to write some code and left. Anyway, what does it do? It says if my DT first value, that text means the text that is inside the DT first value is t, do this DT first value. Error should be this. What is it? Let me show you. Please inter first number. This is our string. You see get text or do string in verse input please error. And the same. If not, for the second value that text, do the same thing. Else return to. If any of this happens, we set this error message. We won't go any further. This never happens and we have false. Instead of writing, I explain all of this to you. I think my video can be a little more compact. Anyway, Let's go up there. TNS starts, set on click listener. What? Of course, if what is not empty inputs. I just write I it just the whole thing. Now, if this isn't true, and this isn't true now, we say true. This has something and this has something now, we say tru now because they are not empty, we want to run the rest. What now? We want a random number. Of course, a random number between let me close this and minimize this again between this and this random number between this first and the second number. So let me write random dot. Next in. It's a default and 50, for example. What does it do? It's a function from the android itself. It gives me a random number 0-50. I can't put any number for example five. It gives me a random number 0-5. Or 70 gives me a random number 0-70. I don't want 0-70. I want a number between this and this. Now I want to say for a start, EDT, second value dot x because I want the text dot two string because I want a string, and of course, I can't give random next string dot to now, I can have a random number between zero and second number. I think it's not ok. Let me just press in there and in here. I say get random number to pass this theme to a function. So all of our words be in the same place. Open and close. It should takes two number. Of course, this is my first number. Control C, and control V and inter and shift and the button next to the M s without shift. Button next to the M and another control V. S, not the second value. I just copy that. E, first value. And of course, V A is equal to the results of this function. Let's just comment this as well. So click in here. We don't have it. This time, light bulb created. So So I have my what should I say? First is ino course and my second is ino course and my result. Let me just say sorry with pig in. So we're here and random dot. Next in. I think this video might became long. Let me just divide it into two videos. We continue into the next video. 56. Day 8: Writing Primary Game Codes Part2: Writing primary game codes part two. Where were we? If I want to have a number between first and second. First, I should understand which one is lower and which one is bigger. Why? Because we're not saying definitely, the first one is smaller. Maybe we put bigger in the first one. Let's just do this press home inter go up, R, what mean? It's minimum variable equals our first. Of course, R max is equal to. Second, by default, I guess maybe first one is lower. Second one is bigger. La now Now let me just add an if if if what? First is bigger. Then second. You see what just happened, and open and close back inter. We say mean is equal to second, because of the second is lower now. And max is equal to. First, you see how easy is this? Now, let's just have in turndom, max that we already decide which one is max minus mean. Peels one. Do you see what just happened? So we say what is Max, for example, we say 50-100? What is Max 100? What does mean 5,100 -100 -50 equals to 50. Okay. Now, we have 50 tell us one. Now we have 51 0-51 is our range. And we add mean to this i because we don't want the range 251. We want from our mean So if we have zero, we add that 520. If we put 50 inside the first, we add that 50 to the For example, from zero, if we have zero, we have 50, and if we have 50, we have 50 plus 5,100. We have this range now, and of co, we shouldn't forget. We should return our number. I have the error for a few seconds and then it's gone. It's Android Studio bar. It takes time sometimes to the error that says, you don't have return will be gone. Now it's gone. We just want to see what does this return to us. How can we do that? Let me say, we have this get random number in here. And at the end, for example in here, I press inter. I say L, what is like, you just going to see. Look do I. Let's give it a name. For example, get random number. So I have this error. I will go and check the light pole, and I believe that things can help me. But since, for example, I'm just a Android programmer one month or maybe one year experience. I don't know much about these kind of things. Exactly because of that, I tried to Reach as many as errors as possible. So you can see what different things might happen to you. Like any other students that I have in person, I saw they have many errors. Anyway, open this. Okay. Import class. Log, create class, log, create om, blog. Wow. What should I do? Which one? I don't know what just happened. Okay. Let me just click somewhere else. I still have this error. If I see here, I have also error. If I go on it on resolve reference like. What should I do? I don't know. I just write like with a small L, and I change it to big L. Let me just see if I write L. What just happened and press I dot, and then, for example. Now, I still have error in here. What should I do? You see if you put your mouse on it, you see import class. I shift in there. And you have more actions with Alt inter but Al shift inter just click on it. Okay. Let me just shift inter. Does anything happen? I'm not sure. Let me just again click on this or when it's open, A shift inter. Okay. Let me just go up. It imports Android UT Log. So I have this now. Okay, I just remove this and I'm going to check what just happened. I still have this problem. Why? Because none of the following function can be called with argument supp. Why? Because I just give it one parameter. But I should give it at least two string string. The first one. You see? Now, I came back, the button next to the M, separate this and say, we have a just up there, we filled a dot. You see this structure, tag string, and message string. This is message. This is tag and we give this message the value of A. Now, the first one is what we field. Okay, let me run the app to see what just happened. But what is it? Okay, I just click on this game and zoom, zoom. A little down. Now, the first number, for example, the 50 that I said and second number 100, and in here, I have this cat. Last time, I think we filled this fit level error. Do you remember Because we want to see error, we remove this level error, and we copy this random number, we paste get random number. I repeat that. I started my app, I came to my page, first value, first number, second number. Now, I have this get random number. That as you can see is for lock. I fill this tag with get random number with the value. What value, the value of A, A is the random number that we just return from this function and put it inside the A. Then we have this A. We can put this A inside our lot. So I convert this A to one to one extreme. Then because we want to find it, we want the possibility that find that value, we give it a tag. This is names, exactly name. You remember that? With name. Imagine you give your value a name. With that name, you can't find it. So get random number. Okay, I just copy that. Put it here. With this name. I say, Just show me the things. Package Mine. What is Package Mine? My package, not the full emulator. Just show me the things inside my package. What is my package? My own app. Not the other things inside that android. Okay. Now, we have understanding of all of these. And of course, on the left side, log cat. Which one Lg cat? No wheres cat? We have some other things inside here. For example, you see this button, Kar cat, Klich or right kick, Kleer Kar cat. Okay. Now, I have this start button. When I press it PTN start, set on click liner. Runs, and then if is not empty inputs, none of them are empty, then this value A. Filled with random number, then I put blog, get random number and a dot two string. I believe if I press a start, there's a number in here 50-100. Let's do that. Start. I have 82. C do side 7624 learn that my calculator. Why? Because this is package mine. What is this get random number? It's the name. I give this value. When you say it's a tag, so later on, you can find that value with this tag. And of course, here mont Day even our second minute seconds and smaller value then second, you have and your tack, the exact time you have and your name of that log, and of course, your package, where is that your application or other application and the value. I have this value of 82. Okay, let's press this again to see what just happened. It should give me another random number 50-100, okay? Start, 70 start 73, again, 69, again, 96, again, 82. Do you see what just happened? I create random numbers 50-100. So let me do something else. I say, for example, here is 100, but here is 50 to see if that if, do you remember, that if this if works, and it detects our first number is big and second number is a small. I just want to see two There's a lot of numbers in here. What should I do? You see this button, Kleer cat. All right lick, and where is Kleer cat? Just like that Kiara for this button. This is as you can see the L cat button anyway. Start 76, start 78, start 83. Now, what just happened? This just five. As you can see, all of the numbers are between the range that we want. Okay. Let me just clear it again and say, let me make it a little tighter, because I want to see, I just want to see if this plus one really is necessary, I'm not good at Matt because I'm not. But I want to see is it good 99 and 100. If we forgot to put this plus one, We don't get the right number. But now I should see am I get my number between these two ranges between 99 is 99 also and 100-99. So 100 or 99. So let's start start. 100. Okay. Start 99. So I have 99-100 and the boat numbers are also included. You understand what just happened? Let me try start start start start 199, 100, 100 100, one, 100, 199, just like that. I have between these two numbers. So my code works just fine, and I have to write these tell us one. And my range is two, as you can see. You see, 100 -99 equals one, but I don't want 0-1. I want 0-2. It can be one or zero, but not the two. Let me just do the mat for you. Comment 100 -99 equals one, and that one hells. Another one equals two. So you give give me a number 0-2 that can be zero or one, but not the two. And since I have zero or one, I add mean to them. Let me just a double of this again. So if it's zero plus 99 is equal to 99, and if it's one plus 99, it equals 100. And how about two I say 0-2, but not the two. I hope you understand it. If you even take your mouse on next in, you see gets the next random non negative in from the random number generator, less than the specific util bound. We put util inside as in, and we generate an intrandom value uniformly distributed between zero and specific util bound the maximum number, for example, the number that we just put is not in that range. Of course, it says, that number should be positive. And you can see. The next line says, it gives you error if you put zero. And of course, we put one to don't have error y because if mean and max are equal, for example, 100, 100, 100 minus, 100 is is zero. So we give zero. We might have error. So we plus one. Why? Because we don't get error even if they are equal. Anyway, let me just try a few more times, or I just remove or I just put it here. No, your code is messy. I remove it. Another, another, another. Let me increase my range. For example, 500100 and start. 443 is 500-100. Another 381, 297. I hope you understand this part very well. And I hope you understand, we should check our code like this, 99 and 100 and put this to see if my code really works just fine. Maybe if I put this and I didn't write the correct code, I see, I don't have 100 inside that. For example, I don't have my second number inside that. I check my code with the slug as you can see. So it's be correct. And of course, don't forget to select your emulator. If you put your phone on and the studio, you should select your phone. So you can see the log of that device. I think I mentioned it's just for me, for the programmer. It's something for that tool you see inside that activity for our view. It's something like that. Log is for me, not for the users. I think it's enough for this video, we continue in next video and just to stop and minimize. I hope you understand all of this very very well. 57. Day 8: Number Data Types: Number data types. Okay. This is our app. Let's continue. Last vision D complete this. I want to just point a few things first. Let me just show you this game activity You see this visibility for our text input layout, Android visibility gun. We have this visibility for other objects as well. For example, we do this for our button. We also give this visibility to our material card view, And I just want to mention other objects like this text view has that visibility property as well. Even this view, if I just paste my visibility in here, this view will be high as well. Do you remember this view for make a line in our app? Before I run the app again, let me just show you You might have this error. What does it say? It say? This line might never execute it? You write this if and close of this end of this if and this part might never happen. And it gives me error. So I just thinking, I should write else and if not, do something else. But why does this thing give me error? It shouldn't stop my act. Error is for what stops your act. It's a big problem. But it doesn't a big problem. Okay, It doesn't execute for what? I don't care. If not, I don't want to give you any errors because this is not empty values, I give you the error. Because of that, I don't have rs, but as you can see, It gives me error and the error doesn't make sense to me. Let me just run the app to see if it's run or not. Because when we have error, the app shouldn't be run. It stops from running because you have problem. But as you can see, at the same time, I have my error and my app press game. My app runs. So what just happened? Let me just even write 99 and 100 and where is my lg cat? Clear this lg cat and Zoom. Another Zoom. Okay, I'm here. 99, 100. Show me. 100, 100, 100, 1019999, 99, 100. So I have a random number 999-100, and also both of those numbers included and my random number is integer. So I can't have 99.5, for example. We understand this, but how about this error? Why do I have the error? I talk this much to tell you this once in a while. Let me think, for example, one or two times in each month, I have these kind of errors when I write a program? These kind of errors Sometimes the bug. Yes, Yes, Let me say like this. Sometimes these errors are bugs. The Android studio buck. Because, for example, this error should be on warning. Even not important warning. It should be weak warning. You see, I have one weak warning. It should be on weak warning even, but not error. So let me just since we're here, check one more thing. What if I say, give me 100-100. In my code, just the first one and second one. Take min and max and the if, isn't true, and we go to random. So I should gives me a um random number 100-100 and it should include the 100 and it should Just be the 100 because it is 100-100 and it's integer. So I don't have any between numbers. I just have 100 because both numbers are included. So let me just check exactly that. Let me show you. This plus one after me do the job. If not, the 100 isn't included anyway. Press start 100 or just clear, its clear 100, 100, 100. I press many, many, many times. I just have my 100 because it's 100-100. And I just have one number between between them. Anyway. One more thing since we're here, don't just memorize it. Think about it. What just happens? 100 -100 is equals to zero plus one is equal. Let me just calculate it for you. 100 -100 max minus mean equals zero los one equals one. Now, I give this random maximum number of one. Give me a number 0-1, but don't have the one. So it gives me zero, and I los is zero with the number means 100, equals 100. I don't have any other number than that zero and I plus it with 100. Think about the codes. Not just memorize them. You can use this code everywhere and all the time it's correct, but you should know what are you doing? Not just write the codes. Exactly because of that, I try to give you this much details. Anyway, as you can see, my error is gone. Why? Because just the second, I write something that this ID refresh and the error will be gone, just like that. Let me just remove it. So if I write anything, those errors, I just show you they're gone. And because of that, exactly because of that, I told you sometime these kind of errors happen and just Andrew the Studio. Of course, from time to time, Andrew the Studio give nearer update and these kind of things became lower and lower, but you should understand these things sometime happens. So let's just start, we stop the app and minimize and minimize and continue So the first thing I want to do, I want to comment this like because I check my code and it's okay. So I comment this. Since it's on the source, you can remove this comment part. Or as I suggest, you write it your own. Let me just go to this activity game. I have this, I forgot to show you. This view is hidden. Our line is hidden. This view is hidden because write visibility gone. All the other objects that you can see has this visibility as well, I just want to mention that. Stop again, minimize, and I remove this line because we don't want it to be invisible. What I want to do. This one input layout guess, not dit guest, input layout guess that we just say visibility gone. We want to show this show what input visibility? Yes. I just double helice Control C and go ta ta tab, tab, and tab, and control I think it's better that I write it in here. But anyway, I have this. How do we hide this? We say visibility. You see visibility go. Let me just go back and say, I want this input layout guess. A property of this, which property, I want the visibility. You have all the property. All the properties are there, but I want visibility because so many of them, I write two find it faster. So visibility. I write is equals to V. Of course, with V dot. I have visible. I have gone. So I write gone, and it does exactly the thing I did in here. Visibility gone. It makes the property visibility equals gone. So with this command, I make the visibility property. Gone. What if I write only gone, can I give the visibility the value of gone? No, I cannot. How about visibility with a small Sorry, view with a small V. View dot. It's something else. No, I cannot. So pig V, view dot gone for make the visibility gone. But I want to make it visible. So which one You see this visible or let me just write in visible. I have also invisible as well. We have three different options for that visibility, and I have invisible as well. Anyway. Let me just visible this. Let me just run the app to see what happens because we want to know. You don't have to run the app as many times as I do. Anyway, five and 55. If I press start, input layout guess should be visible. Start. Oh, your guess, it's visible now. Just like that. We make it visible. I want to make another thing. This go 110 PTN go. I want to make it visible as well. We give this visibility gone, I want to make it visible. I want to copy. I want one copy of this line. And I don't want to copy it to other Ps. Sure. So what should I do? Control. Let me remove this. Sorry, I just press Control P D. I write it like this, so you can easily read it. So I write control. I press control D and my line duplicated. Let me just do that again. Control D on my keyboard. Control D. Just the line next to it. I have a copy of it. It's just like I pre selected control C, and then came here and then pressed in there and then control. Oh sorry. I even do that wrong. Control C, and then inter and then control V. It's too many sets. You see, select control C, go to the end, press in Control V. So what should I do instead, I just go on the line that I want. Press control and then D. I duplicate it. So you understand the triage. Let me remove this line and I'm not going to activity game to copy the name of To. I just want to write it in here, BT go. Since I say we should write, I just write it in here. But sorry, I don't want to even copy this controls. And I told you a new anyway. So now we want to The user guess the number, and then we store this number, this gas inside a variable and then check it out. So we should define a variable. Instead of be in here since I want this variable to use to be used in other places, I want to declare this variable gb. So I just remove it from here. Let me just go up up up just after this binding, it's also a global variable. Let me just say variable Not a random number. It's a good name for my variable. What is this number type? We talk about types later in this video. But for now, let me just give this in. It's an int. Is it good? I go back. No, y please, give it a number. Add initialize there. I should give it a number. I came and say, Okay, You do this. The Android studio give my variable, the number zero. It's okay now. I also can give it null and give the number later. But I just say, give it zero. But since the zero can be one of the guesses, maybe I should go to minus. For example, minus one out of my guessing range. I think it's better. Let me just go to main activity. I open this main activity. Do you remember we have followed in here? For decimals, we have followed and double. You see, we talk about it. Flowed and double. And we say after the digit after the dot after the point, the decimal umber in fallowed is about seven number in our test and for double is about 16 number after the decimal point? So we talk about them, and we also introduce int. We say, you see. If you are less than 1 billion, you can give it int. If you are going more than 1 billion, please don't give int. And also talk about a string B and fot. Okay, I talk about fot and do now. Let me just close this and continue. So as I say, we have many other types for integers. We use lots of times in because it covers many things, but we have other types. Let me just show you. Where should I write? I think in here is good. A equal is the type of byte then. B what happens if I don't write that? For example, just want to write short. I can't. I should add shift and the button next to L. If not, if not, it gives me error. I should write it. What if I write a small S? What happens? I have error, so just capital S. I cas sensitive. What's next? C? What is it? Of course, with big. What's the fourth. Long. Sorry, long. I think I mentioned in previous video, we're going to talk about long. Anyway, what's the difference? For example, if I want to give not even 1 billion 100,100 million. It gives me error. Why? Because BI can't have this much big number. This kind of number is too big for by. Let me just remove 200. What about? Not even one. I usually use it. Then my number not going more than 100. I just write. Byte is -128 to 127 when I value is lower than 100, I use byte. I don't like to go the exact capacity of variable. How about short? Short is from -32,000 7682 Pella, 30,767. So let me just check it. If I give it one. Is it okay? It's okay. Ten. Is it okay? It's okay. Hundred 10,000 s. Well not go beyond 2000. It's just 10,000. What if I say 100,000, I have a row? Because I can't give more than 32,767 in this. So it must be lower. You see, I say exact number, it's okay. But one more, it's not okay. You can't give it even one number more than that. So when my range is less than 10,000, I use short. But many, many times I use int because it has a big range and For many different things, I use it. My incapacity is just like this. Of course, it takes number to 2 billion, but I don't want to give it 2 billion. I give it less than 1 billion. It has the capacity, but I don't want to fill the capacity. You see the bite. It said, it's okay to say bite because you want to use bite. You see the short. It said it's okay to give short. But sorry, I should lower this. It's okay to give short. But you see in it's different. It says you can remove int and just give it the number. Let me just show. You can remove this int. If I click on it, it removes the int declaration. Because by default, as I say, the int is most common type of variable, and the cutlin give in itself when you put a number inside the variable. Because since we're teaching, I put in. So we understand that int is default. How about long? Just write it down in here, so I just can copy them and give them in here, put them in here and paste it so long. Can you see the difference? Okay, thousand million billion. Oh, my God. Thousand of billion billion, million of billions. And 9 billion billion? I think you can't count the number. It's a really big number. So when I use long then my number, it's go more than 1 billion. Of course, you have the maximum number in here as well, but it's very big and it can calculate and accept very big range of numbers. Long story short, why there are these different types? Because each of them has different capacity. For example, let me give you explain example, for example. If I have a tank with 1,000 liters capacity. Is it okay to use it to a sore only one glass of water? It can, but it's not reasonable. For example, if I use long to assore the user age, it can do that, but it's not reasonable. It's most common to use in sometimes if you store many datas, many times, many repeatable datas, it's better to use less consuming datas, like these or these if it's possible. But if we use only one or two or even ten numbers, we usually use in. If you can't put your number inside in, for example, population, You can't put it inside this or many other ts. You say, Okay, now it's time to use a bigger number. For example, long. I have one more type if you can't put it inside Long. Let me just show you that R, I give this a name. E, what is the type B integer. We give big integer to this E. It is very big. Okay Let me just give this big integer number, one, two, three, I can't y? Because it's different than the others. I should say in this way. Big integer. Sorry, remove this dot value of one, two, three, for example, four. Let me just continue this in next video because I want to create a function and not put them like this. 58. Day 8: Big Integer: Peak integer. This is our app. Let's continue. Where we. We want to put this inside a function or just write a four. Let me just write a four. I just press inter. I write four open and illos. I n 050, for example, and it adds the to let me know, it starts from zero, and it goes to 50. So I have my i from zero, then one, two, three, four, five, until 50. L et me continue to see what just happened. We'll just make it 49, we run it 50 times and we give this 50 as well. Run our code a few times. How many times as many times as we decide. For example, I decide, I do this 50 times 0-1, two, three, four until 49. And if I want to see I in which of them, I can use this I inside the four. And each time this I has the value of zero, next time one, next time, two, next time three. Anyway, let's continue. I say E, E variable is equals. So I want to put something inside my e variable. Again, e. So until here, I put E inside my E. Dot multiply, and I can put B integer. Inside this, I write integer, and again, sorry, I remove this dot value of or no, just 50 it's okay 50. So I have 50. I multiply this 50 with 50 and store it again in E. And after my four is finished, let me say like I open. I should say a tag name. Let me just say E, I can't give this like I the E. Y? Be it should be a string. Let me just show you this I should take a string value from you. See a string and a string. Tag is a string. Also, the message is a string. So I should give here a string the tag and the message, of course, should be a string. So You have to say dot twist string. If not, you have error. I put my E, my big integer inside this log, and of course, big integer. I give the tag, big integer N. Let me just run this thing. Even I don't need the function now. Let me just run. The cat, I clear this, let's go to gain. Get random number. Yes, we put this to see only get random number. But we don't want this. We want big integer tag. Control C, go here. Control. Why? Because I want big integer. If you don't do this, for example, big integer one. You write something else. What just happened? You can see your result. Imagine you use this like many times, and if you write any of these wrong, you can't have it. Or even if you, for example, write here, Big integer one and somewhere else, Big integer two, if you just write, for example, Big integer 11, you can't see any of those. So you should be careful. The same thing, you want to see them in the same category. You should be careful, give them the same cat, so you can see them with each other. I hope I say it clearly. So what do we have here, big integer. Let me just see the number. Okay. I'm not very good English speaker. And if you are, I believe even you can't read this number. Let me just count how many number do I have? Let me just say, if this much is about ten number ten digits. Sorry, ten digits. I think it's about even more than 100 digits. And honestly, I can't say any name for this number. So you can see how big is big integer. First, I want to show you something in my log, and then I go back to see what do we have in code. Okay, stop, stop, minimize, minimize, and as you can remember, control D. I have, for example, these two, and I can say heels string hes, string, and inside here, num one space equaled a space in here num two, and space of course and the space. Let me just run this again. I just clear like that. Let me just go to this page. I have big integer b integer because I give the t this name, big integer, so I can find these two with big integer. You see the time is the same, Because we clear the older one. It's almost important, I can't say rule. It's a trick. You see, I have this data, but I have more description because I have a string, I can add another string to it, so I can put number one is equal D, and number two is equal this or even in the start. Then when I say pig integer and I have five or ten different pig integer or any other thing inside my app. I log them all, but I can't understand. For example, this number, it's from there. I not remember this number, which one is this number? I add something at the end or at the beginning. So I can understand, this is number two, it's this one. This is number one. It's this one. I think after at let one or two years of experience, you add some of these tips and tries to your code. It's not really the thing anywhere teach you. It's just experience. Let's just stop the ad. As we understand, we can say the texts and pelos, what is in here, for example, game acti even line for it. Even this. Okay, I'm in that code and line somewhat in that line, that activity, and there, I have this data and it's this. And then when I check my app, all the pig integer. Why do I say Pig integer? For example, data data test three data test from database, any other place. It's just the name. And When I check it out, I can easily understand. Okay. So I have that data with those problems. Okay. How can I find that data? Because, for example, I add the log 200 plays, and I'm looking for that error many hours. So, I can understand. Okay, this run data is online 40 in this activity, and this is the round data. I hope I explain it simply and you understand what just happened. Okay. Let's talk about this codes. I say V E is a big integer, so my variable named E is the big integer and I want to give this E value. Let me just come in the is and say, Okay, give it five. Is it, you can't give it five. It's not by short in or ling. You should write big integer value of something, so you can give it the data. But the number, the number. So if I go in this error and open it, the change type of e to t. Do you want to give it five? Give it to int. Y big integer. What if I say, k, big integer value of. For example, even that five. It's okay. You can give it. Then what happened? We add a four. What does a four do? A four, repeat your code for definite times. So what just happened? I say, I need a four and I call my variable for that f. I can't say anything. You see? Let me just say ABC, for example, and I say capital A num ABC caps and Never use it. Why? Because I don't need to use this value inside four. I just have this and each time this increases. For example, first time, if you check what is it, it's zero. Next time, it's one, next time, it's two. Let me just show you that as well. I comment these lines. Copy this in control V and big integer. And I want no Myb C to string. Let me just see what do I have? Run the a again. Do I have any cat? Yes, I have. Clear it. I clear it, and I say, I want I. I don't have any. Let me go there. And until 49. From here, let's go up up and equals to num two. You see equals to num two. This one. I just want this one. Because Autopil manager also has by mistake, autopil manager. You can also see that as well. I should put a longer name, but it's okay. Let me just see what is the data that has equ two. I first time that my four runs, I have zero inside this numb ABC. Next time is one, two, three, four, 56, and it's until here 49, it less or equals to 49. It runs until it's equals to 49 and then it's done. If you count it zero, 249. Since we have the zero as well, we have 50 times of run. I hope you understand this part as well and stop this anyway. So I commend this as well and change it back to No, I don't need to change it back. Anyway. Let's continue. I have zero, one, two, until 49. So we understand this part as well. And as we already say, I want to give this big integer the data, but I can't put it with equal sign. So I should say big integer dot value of this number. So I have 50 inside my E. In the first run, I mean the zero ty. I have this like this comment. 50 This part e equals 50, dot multiply, just like this star for integer. So we have this 50, we multiply it to a number. Just as we can see dot value, we multiply it. Just like you put that star. To a number, to what number? We say. We just can't say, Let me just control x and instead that say 50. We just can't say that. The integer you can't put it inside the big integer. So you should say it's wrong. You can't put the number like that. You should say big integer dot value of, so you understand it as a big integer. 50. So the first time, I have 50 multiply 50 equals, I'm not good at mat, but I think 25 and 20. You can put it in calculator. I think I put the right number. It's the first run. It's the step zero. What about the step one? In step one, I say, you see this 2,500, I put a 2,500, I just calculate it and put it inside E. I have in the second time, I have this E with the number of 2,500. So I multiply it again with this 5050 equals two, I put it on calculator and C. I have 125,000, and we do this until step 49. Exactly because of that, we saw that very, very big number and we see the capacity of big integer. Big integer is different with these simpler types, and you use it very, very rarely. But if you need a big number, you should understand there is a very big number inside this language, and you can use them Just in time, you need them. Even this line, we use it when we need it. Also, before I forget, we have different ways to use for. This is only one way we put two dots. Because in this lesson, we don't want to talk about for a lot. Just you should know there is a four and I stop talking about different ways and talk more about four. In the future, we get to know about for a lot. We use it in many different ways. Just be patient. Just to be sure, this multiply is just for this big integer. For example, if I press inter and say this D, this is long dot. I just go copy this to be sure, all the word exactly the same. I don't have it. You see? I don't have that. Why? Because long doesn't have it. How about in? I have minus. How I have d. But how about multiply? I don't have it. This is just four big integer. This type. Long in doesn't have this. Doesn't need this y because I just can't say d is equals d multiply d. And it says change to y. Why? Because you say y. Okay D error. No error. Why? Because you don't need multiplier. You can't just use this star. This big integer, as I say, is for specific works, very big numbers, and heavy data. And because of that, it's not with regular multiplier. Is this special command for multiply the number. And even the input that you want to multiply with that should be big integer. I just comment this with slash star and where we finished star slash from here to here we comment it all. I leave it here. If you need, you can uncomment it. You just have to remove this part, and of course, the end. I just comment it again. I think we talk about this kind of comment, multi line comment, not just comment one line. If not, we just saw this again in here and we get familiar with this. I continue in next video. 59. Day 9: Checking the user's guess Part1: Checking the user's guess part one. We have this game and in this part, we want check the user's guesses, and of course, show the result. But we also cover some other things. For example, null pointer exceptions, or even the like. Let's continue. Okay, well come back. Before I start, let me just talk about four a little bit more. We just write in here R four, and in this four, we should say we have a variable. For example, i, and we say you can say any other name. This variable should be in a collection or in another word arrays. Since we didn't talk about arrays yet, I think we should talk about them and have more example of this in the future. But as you remember, we say or in a range of number. We don't use in arrays yet, but instead of arrays, we say, for example, f in between zero and we won't say until another number, we say dot, dot until what until ten. We have four 0-10. If I just say like, I just copy this. I don't write it again. You see after four, we have opening And when we're finished, we have closing. But in here, since it's just one line, we don't have to write that. Anyway, we don't have E because this is comment. I just say I. Why? Because I want to see what is my i. And I say I value, and I don't change it num two. Why not? It's something for no reason that I just write. Let me just run the app to see what just hap. It said in a sal successfully in 2 seconds, but I'm waiting for about 20 seconds. For the first draw when you open your Android studio, it took a few a little more time. For example, 20 seconds, it takes 20 seconds to run. I just want to say L cat, and I want to clear this and my eye value. So I copy this control C and delete this control V, my e value, and of oom out, and we want the game. Again, like that, I just want to loom and click the game. My eye value, you see my eye value. I have this my eye value. What is it? It's start from zero, and the zero itself. This one, and it goes until ten and number ten itself, zero to ten, zero to ten. If I count nine, ten, 11, we run 11 times because one to ten, and we have this zero itself 11 times. Can I write it in a different way instead of these two dots. I can just write until. You see that dot, I have it, F zero, two, ten, zero itself, ten itself, and I just select these two dots and say on. Is there a difference? Can you see any difference in here? Look at this, this. I think it doesn't have equal part. What does it say? If I stop the app and run the app again, And I just see the cat. Of course, clear this cat with this button or right click. I want to go to game. It said from zero, one, two, three, four, and until line. Why? Because I don't have the equal part in here. If I write until instead of those two dots, I don't have ten itself in here. I hope you understand this as well, Let me just write another thing. Stop the. Of course, and minimize this R, what? Max I, for example, Mx equals ten. Then I write in here, Max. Is it okay? Let me run the app and check Run. Of course, like. Let me this time leer this pot, Kleer, and click the game. So I have 0-9. If I change it, let me just change it to eight, and of course, clear. If I go back and press game, I have it until nine. Why? Because I change the app, what my APK is already installed in emulator. Don't forget. And pay attention. My app is already on the run. I change this number. And I didn't see that. So I go up here to see I have drawn. I pressed this button as well. I'm waiting and it runs again very fast. Less than a second. And of course, click Logcat again. Clear this logcat, click again. And now I have it 0-7, not the eight because I re until. I hope you understand this part as well, and I want the eight itself, Let me change it, dot, dot. I should have the eight. Let me clear this and back, click the game. Where is the eight? I don't have it. I. Let me repeat this again. You should run your app. This is your old app. You change your code, and it's not effect in install app. Let me put it this way. Imagine you have your output, you install it. On your phone, you disconnect your phone. And whatever you want to do in here, it doesn't affect your phone anymore. This app in installed and run, you change your code. So you should press Run app, then your new codes, and whatever you do effects. If you have an error, you fix these things, you should rerun your app. If you do any other thing, you want to see the effects, you should rerun your app. Even on your phone, you should re in solid on your phone. Again, cat leer game. F028 and eight itself. Now this is something so I understand one thing what? I can put this number inside a variable and control it. How about this number? For example, is it okay if I say R mean is equals zero, We have error, y because I put this space, and of course, I want big I in here. I use this mean instead of this zero, mean. Is it okay or do I have arrow? Let me run. Of course, we go to check users guest, but, since we talk about four, I just want to check all of these to see if these things are okay or not. Ga, it's 0-8, and if I change it to anything other than zero. For example, I say five. Again, if I go back and came again, since it's a salt app, it's not updated yet. I didn't see anything. I don't do anything. So run the app again. Like C. Clear and game. I have five, six, seven, eight, um five and five sel, 28. So we understand that. Please write all of these things with me step by step. All the courses, you shod write these things with me step by step. These things important, and you understand these things anyway. F five, and five itself. 678, and the eight itself. It's the different between these two dots and t. Okay, I think we have enough examples in here, but I still have this question. And as I say, let me minimize this. You see, because it's one line, I don't have shift the button after p and closing, shift the button after two button after p. Closing. I don't need this. But most of the time I write it. Why? Because I might add codes, and if I don't write this, for example, let me show you that example as well. D, D is. And What is control D? Do you remember? What does it do? Control D. I duplicate this. First, I have this error. Why? Because it doesn't recognize, because you're outside of four. You don't open on allows, only the first line runs. But since I want to show you, I can simply remove this and say, num one, one, two. To show you what's the difference? Imagine you forgot to open Akos. You say, it's one line. Any comment any other thing you want, you write. Okay. What you forgot. You forgot what? You forgot to open anks. Another time, you add one more line. What happens now? Let me rerun this Logcat leer gay. I have this line with 45678. But this line four doesn't run this. Please run these codes with me and see it yourself. These are important. 5678, but this only ones. If I consider that this must run with this four, as well, these two lines are together. I don't receive an error. You see the app doesn't say you have a role, but my app doesn't work as I expect because this only runs once. So if I say it starts in here and ends in here, shift peels, the button next to PN, the button after that. So I have this ands. Let me rerun and look at and clear and game. I have five, num two. I have num 112, and again, six, and again, seven, it runs runs every time with me. With this line as I expect. Because of that, most of the time, I put these on my four, even if on my if I can eskep that, but most of the time, I do not. One more thing. I have a really, really important question. Why do I use four? I use 42 do a line, a bunch, I can't say a line, a bunch of code because it might a bunch of code or specific number of time. And I can have those number of times with a certain index that is lower index, and upper index. If I say five to eight, I have it five, six, seven, eight, four times. I run this code four times both of these lines. But what if I say I don't want it. I can run this code for myself. You see, control V We run this code one time. Y four. I have this question, y four. Let me just just do control D. You say you want to run this code twice. Control, I have two of this code. We run this two times. Even if you want that number, I can give zero and one, I have zero and one myself. Y four. Okay, let me just continue of this action and say control three more times and say, this is two, this is three. This is four Is it good? Let me just comment this and say this is 0-4 itself. If you see, I have one, two, three, 45 lines, and I have one, two, three, four, five lines. It's the same, I have five lines. I have five lines. These are equals. But one more thing, first of all, I can't control the numbers in here. I should write e and check, and it's really complicated. It's not recommended at all, but we want to try. If we write like this or even more, 20 times. What if we want more? Should I change everything and have any other kind of s and what should I do? I write, for example, 500 lines, and I have 500 es to check what is I and if I run this line and check it on ef. What if I have error because I write something wrong in one line. It can't do like that. Especially you have five times in here. Imagine 40 times. What do you want to do? Let me go bigger. 100 times. What do you want to do? Do you want to write it 100 times? No, you can't. How about 1,000 times? Of course you can. Because of that, when I want to repeat my code, repeat my commands certain times I use four. Four is very useful command and we use it in many places. Instead of this or write it 1,000 times, I just write very short code. It is clear, I can understand it. I can't debug it. It is really simple. It's very good and efficient because I have less errors as well. It's really fast because I write it fast. Saves time. By the way. I just in here, star slash and in here, slash star. Why? Because I put this for you to see as well. What is our previous videos? We talk about these numbers, where are they? Byte for about 100 maximum from -128 to 127. Short, a little bigger in, very big long, even bigger than in, and even we talk about big integer. Why do we talk about all of this? Because I want to see which of these variables is good for me. For example, because we want to guess a number, I think bite is very little. Short is good. Most of the time, I use in and Android default is in. But let me use short. I just copy this part, Control C, and take our short variable to get random Control V, I add slash, of course. We want to give this number, for example, minus one, and we Put this control x. Let me just take it and put it in on top our code to its a global. In here. We want it a random number, good name, and instead of p short equals to minus one. I just clean. This I have random number short equals minus one. Since we want to change the value inside our code, I should say, not that. I have variable random number short equals minus one, and I say comment This is the range of short, so you know, this is the range of short, anyway. Let me just select this by double click on it. You see double click. If you click three times very fast like this, one, two, three, you select entire line. But if you want to click one time, you change the place you are here, here, here. But if you click two times, you have double click. You select this part. Control C. S If I teach you so many details, it is important to me, so you understand every of these things. Anyway, let's go down random number. Control V equals. Oh no, I have error. What just happened? What's our error? Isn't this random number? Short. Yes, it is. Let me just check. Short. But what is our get random number output? Let me just check that as well. Control and click on it. Let me just go back in here. Control on this press control and click to see the destination. Let me say so. To see the sores, get random number. What are we Bring to our variable. We return int, and in that place, it says, you can't convert in inside that short. In some places, I should change this int into short. If I change in here in short it's okay and I can't do something else. I can't change it to short in here. I say, do something with that method for me. I want to change it, I even don't write anything. You see, too short. I also have to a string that we use it many times to in anyway, too short. We have our int, we change it too short, and then we put it in random number. As I told you, I always most of the time, sorry, most of the time I use in. I just want you see how can you use the short. And if you go up and change this short to in and go back. You see. Now it says, why do you have short inside that in? You should convert it again. Let me just see. Can we just say that in? It's really, really bad. We can do this, but I don't want it. Anyway, instead of have this in and change it to short and then change it to in. It's not a smart at all. It's really bad. I just remove this part and it says, it's short. I say, and remove or just comment this part. I have this int inside my int. Because we change this variable into in. Let me just check it again. You see, my variable is in. Since I just want to see, where did I say random number when we declare it, and what does it type? Maybe other minor thing, for example, our default value. I want to check this variable. I press control, move my mouse on this. You see you can see it in. But no, I just want to see the line that we declare it. I press control and click on it to see, it's here. Let me just do that again. This is my random number. Press control, click on it. Oh, this is my random number. In here, I give this value to it. I can change it to minus two, for example. I can find it very fast by just click on it. Simply like this. But how about other variables? Like for example, this binding, I want to see where we declare this binding. Maybe to double check, change it or any other thing. I press control to see is it working as well? I click on it. After press control on your keyboard, I click on it. This is my binding. Let me do this again. I'm here. I see, I have this binding. Where do we declare this binding? Press control, click on this binding, Oh my binding is in this line. So we continue in next video so our video won't be so long. Thank you for your attention, and I hope you learn a lot of these important tips and tricks. 60. Day 9: Checking the user's guess Part2: Teching the user's guess part two. This is our project, and we continue. Now we have our random number. We store it in this variable just in here, and we want when user inter the gas and press this go button, PTN go. We want to see if it's slower bigger or the exact number. We want compare that guess with this random number. We have our set on chylic listener on PTN art that fills our random number. But we don't want PTNS start now, we want To see when does the user click on PTN goo. Let's write. It starts in here and it goes. You see the line until here. I just click. Press on inter. I write Pt N. G. Inside this PT and go, I want to set on click listener. I press that and say set on click listener, I have on Klick listener. You see you have two of them and you can see the difference. If I click on the second one, what is the difference with the first one? Let me just click on the first one. I have the parentheses and it gets input. What is the input? Or we just shouldn't talk about it. Anyway, if you click on it, by mistake, you have this and you have open and lows. Shift next to the P and of course, the lows if it didn't add it, but I should control the space again, the, the second one, that have that range for me. Like this and no parenthesis. Then when it puts my cursor selector on there, I just press in there. The closing part goes down there and I'm in here. Android Studio arrange it for me. Anyway. Let's take this your guess value. But I should check to see if it's empty or not. Let's write and then I can just press in T. No write open and kilos. I write open and lows for me. I write Tex ts. Text utils is for android itself. It gives me the possibility This is much possibility. Which one I want to use, I want to use the is empty. Why? Because I want to check if my text is empty or not, and of course, it returns bulion for me. So I can use it in true or f. Anyway, is empty. Let's write e t, et gus, this one, dot text of course is empty or not. I press and shift the button next to the P, and of course, the button next to it for lose, I go back one character and press in there. If it's empty, what should I do? It's empty. Et gus, dot, I should show an error. Of course, error is equals to shift the button next to the inter. I press one and it adds another one for closing. I can write my text. Shift and P for Big P. Please, in your Yes. I think it's a simple and reasonable text, but I should put all of my Text inside a string. There is a string string, and I have two languages. I should put this string inside my strings. Of course, in Arabic version as well. I just click on this text that I write and I press old inter. You see this extract string resource. I click on it. Resource name is please enter your guess and value, and of course, Arabic. Of course, I press home and write STR, shift that writes for me an underline. You can write any name you want. I always write STR before my string resources. But it's up to you. And if it's too long, we can make it shorter. For example, if it doesn't fit, I remove this your part. So it becomes SDR, please interges. I remove those parts that makes my string a little shorter, but still my name should make sense. So I I read this name, I should understand what does these things do. And what does it for? I just click on, I have this r dot string SCR please interior guess. And read the studio, do this for me. Of course, if I go to the string, SCR please interior guess. I have this with value, and in Arabic as well, we didn't translate the other. But you can see it. You can translate it anytime you want and I just close it, close it. Even if you don't want to open it from this project, you can't press control to go to the source. I just click on it. First, I press control and then click on it. It says, it came from two different dos. Why? Because it is English and Arabic. So I say, which one do I want? Show me the English one. This is the English one. But if I say control, click. Now, show me the Arabic one. It goes to exactly that line and I can see inside the Arabic one exactly that line that takes me there and I see the value. Anyway, close this again. Besides this, even if I click on different things, for example, EDT guess, you see this DT guess. Where does this DT guess came from? Press control and click on this. I want to see the resource reference. Click EDT guess came from here. This is my EDT guess. I understand now. I think I didn't mention, with this get a string, you take your string, get a string, and for taking it, you should give it the resource address. Go to resources, then go to a string folder, and of course, a string foil and take this string folder. Inside that string folder, depends on your language. Now, take this variable that we give the name. Resources, a string folder inside that string. Take this SCR for me. Get a string, do this for you in here, but how about our view? Inside our view, let me just click in here at sign a string Slash. This takes a string for me. It's the same thing for taking the string equal with this get a string. So we have this if in here, if this is true, do this, if not, we want to say, if not, do this the next part. If it's true, this part never runs. These codes are really small and not line. But for learning, I think it's better that I add a function. Anyway, even for this, I add function. Check guess, of course, we don't have any check guess. We click on it and we see this light bulb. We click on this light bulb or inter. What do we have? Create function. Let's create function. It creates a private function for me. What is this private, as we already told, this private means you only access to it inside this game activity. So I remove this to do and I say, let me just put an input inside it. What's this dites? We put this inside here. Of course, do text because I want the text, do two string. And do to int. It gives me error y because this fun doesn't have any input. You see it's empty, but you give it something. You see the next one has input, but this one doesn't. I can came here and write it myself by hand like this. But let me just see if I click on it and see this light bulb or this in there. I want to show you the boot way. I have these options. I say, Okay, add it for me. Click on it. It says, Here you are. This is in, because we convert it to in. It says, Okay, I make it in because you give me this in and it gives some name to it. I don't like the name, so I just click on it and change the name, the rest and read the stud do it for me. So what name is good? For example, guess is good. Our guess number cams in here. You see how easy this? I don't need to return anything. If I do, I can add it in here. You see, like this. What do we want to do? We want to check if this guess is equal grad or lower, then This random number. Let me just say if inters is equals to. Remember, we have two of these four equals two because we want to chick a condition. If you just add one, it's four, put some other data inside the variable or object. You put two to check if the left and the right side is equal or not. Equals to what? Of course, do random number. I can just close it again to arrange it for me, just like that. If they equals, what should I do? I want to inter, please explain it for yourself. Understand what are we doing? We even don't have to create function for these small things. But I you understand with these things, you arrange your code and how do you do it? Try to make you type these things and learn better. If it's equal, if it's equal to our random number, I want to show our result in here. So, I want to show inside this txt. Txt result. But let me see, I don't have tx result because it can understand what do you mean by by txt result. Why? Because you see this apply, it's open in here and it close in here. If I say txt, I have txty result in here, but You see, I don't have it down there. Since I don't write binding apply in here, I should write fair binding. You remember the access to our objects inside view with view, find view by ID or binding. We do this now binding. Now I write that. I have eight gues, no, PT and go, no, I want txt. I have this three txt. Why do I write txt before their name so I can find my text view text views really easily. These are my rules. It's not I have two, but it's better that you have the rules. Anyway, Tt result. So I have error. What's the problem? Do you remember what should we add after binding? I press on this light ball to see I can have this question mark or this that came with shift plus number one. This one, this one, you see on the right side, you can see like this or like this, like this or like this. Because it can be null? O binding can be null? We talk about it when we declare our binding variable. Of course, it's not null. We give this we give this nullable binding. We give this. Data, but it can be null. Because of that, let me just go back. We have to say, It's okay. Let it go. Of course, we say what is null? Null is nothing. It's not a zero. Null isn't zero, null is nothing. Absolutely nothing. I say, Okay, put this question mark for me. If the red light bulb doesn't go, I click somewhere else and came back. It's gone. And this question mark means if it's not null to the rest. We don't have any error. As you remember, with this question mark, we say don't run it if it's null, but if we stay the second way, we say I'm sure it's not null. If it's null, it runs and if gives you error. I think we should talk about this kind of errors a little bit more. Maybe next video. So I can't be sure you learn this part very well. Of course, you can use like this if you check first. How can I check first? I just write if what This binding is not null, just like that. You see how can we check, is it equal to this, we can check if it's not equal to. I say if this binding is not equal to null. It's, then go to the next line and run this and I don't open and close the area because it's just one line, but I can do this as well. I can't be sure if I have many lines, it doesn't go to the other lines as well and I can close it again to sort my code like this, this line, after that, this line, after that, the inner part again, and finally, this one is go one tab for there again. Anyway, as you remember, I try to never use like this, even if I can write this kind of if. Let me just continue in next video. So our video won't be lying. In previous video, my video became a little bit lying because I love teaching and I forgot about T Study. Let's continue in next video. 61. Day 9: Checking the user's guess Part3: Checking the user's guess part three. This is our app, and let's continue. As we just talked about, so we have this binding and we give this value and we use it even if in this set content view, we say like this that I'm sure my binding isn't null. It's okay. Because I just give this the value and I just use this kind of. I'm sure when I just give the value. Otherwise, question mark. But even in here it's okay that, you put question mark. So you get used to this. And you see this error. If you go up and came down, it's gone. It's ID E b. And sometimes the IDE itself gives you the error. You see ID internal error. We click on it. We give report to Google and next version, these errors and bugs became less and less. Anyway, you just press this and Kos. Let me see. Can we learn anything more in here? Because even if we talk about this if, this is also possible. It's equal to that question mark. If I don't write this and of course, this and I just put that question mark in here the same. I have an idea. Let me just even comment this and go up and what happens if I didn't give this binding the value? This set content view doesn't care if you run this code or not. This set content view want something. So, I didn't give this binding the value. And I say, Okay, if I didn't give you anything, don't run. So don't run this part, but set content view still want something. Let me just run the app to learn a few more things in here. My app just came up and I want to see the log, and of course, my eye value. First, let me just click on this game. Beginning of crash. I don't have the crash. Why? Because you see my eye value is in here. It says only show me The logs that have my eye value, but I don't have it. Let me just remove this. Oh, I see my errors now. This is my error. I have my error now, in which process, in this process. This is my package name. Even I have my process ID. Good. Look at this first line in here after this process ID. I just go, go. Of course, I see this game activity, my game activity. It says cannot add a null child view to a view group. You put null in here. And what else do I have? I go down. I have caused by. Not all the time, but most of the time I have these caused by. You see the text cannot add a null child view to a view group. Let me just cannot add a null child view to a view group. You see the same takes in here, you see down there. Most of the time, simply, I just came down to see What is caused y. One more thing. You see you have this view group dot Java view group dot Java, line, line, line something, line something. Those classes are for the Android Studio cling on. What I want this line, y, this line. Because of cose, first, this is my own package name. This is my package name. Then after my package name, I have this game activity. This is my game activity up here. Then I have, let me just go a little up. You see this create, I have this create. What just happened on my act on game activity on the create. And of course, I have a link in here, game activity dot cut line 19, you have error on this line. I I just click on it, let me just go some the risk again in here. I'm in here. I just click on it. Show me this package name, this activity, create and exactly this line. It shows me this line. Click line 19. Set content view binding route, you have on there. If I chek Java errors, of course, they're the places error created. But I shouldn't change them. I should fix my own activity. So I find my activity line 19, and I say what is caused by Song is so short, this caused by and this first line. Of course, third line, this line, this third line after process ID, first line, and case line, I read these two and inside all of these texts, you can't read every line, every letter and all of those classes. I find my own codes and classes and I go inside my own codes to find what's wrong with my codes. This also helps me because it says what's wrong. Most of the time, when I want to search error, I search an error, I just go the legs and search it or from here, from here or just this caused by search this with some keyboard, for example, if I cannot find the proper thing, I add some other texts to my search. You see, if I go down down, I have even this much more. So I have lots of data inside my error, but I show you, I just showed you these these and these are the most important part, these three part. Let me just minimize this and this and see this. If I write it like this, shift one, two times or just if I put it like this, it gives me null. It says, I can't accept null error. If I put it like This, I won't run, because it's null. I equals nothing because it won't run. I also have null and set content view can't take null, and I also have error. Why? Because I don't have error in this, I have error on my set content view. Because I put que mark, it equals control X with this with nothing, and it gives me error. Because I have to put something. What if I just copy this, we give the binding this data. What if I just copy this and say, you want this data here, but not this, I should say, dot, route. Do you remember we write root and at the end of our previous command as well. So take the root of this game activity and put it with this game activity, connect these two to each other with this content view. So I think I make it right exactly this data and the root B this is exactly like I say, Binding dot root. Exactly, I put that data inside here, and then dot root. Let me just see. Is it okay? Let's run the app to see together. So I run my app, L cat. I don't have any error. Of course, first I should press this game button. I minimize this. My view is here. No problem. S content view, work. It works. Now, let me just say ten and 20 start. What just happened? Nothing happens. Why doesn't happen? If I press this start, we should do something. If I press this start, that click lien, should do something. And even should these two be visible. Why isn't? Because we say if binding is null with this question mark, doesn't do the rest from the start of this apploy until here. PTN go and PTN a cart. Parts won't run. I press a start, but these two visibility doesn't change. I didn't take any error. It didn't crash, but it's not working because it ignores in these codes and in here, these codes, and of course, the rest from the start of apply until the end of it. All of these are ignored. Let me just check and change it. So It's null and we didn't give anything to it. So it's null and it won't run. Let me just show you this way. Shift number one number one. It's still the old version. We should run this again, press here. Let me just see what just happens. I go to that game view, but my app just closed. Let me see the Log cat. I have these errors. What is it? Null pointer exception. Do you remember? I say, you can read caused by Cause by, which one is responsible? Who is responsible. Null pointer exception is responsible. Where does this thing happen? Inside game activity line 55 kick inside here. Because I just say I'm sure but it's not. You see, it's null, and what about line 25? It's the place that even I call that function. I call my innate listener. Even when I call this, it says, Yes, you can see and check when you call that function and you should check where the error happens. What error null pointer exception. I even don't have to click on anything on that view. Why? Because in here, then create happens exactly the time my view opens. This function called it caused the problem inside that create and inside this, this line gives me the error inside this function. Even I don't have to click on anything. When create happens, we have that error. Anyway, long story short, you say, I'm sure it's not null, but it's null because it's null, you have null error. You might see this in other places. It's really good to get familiar with this and know what does these things cause? When does this thing happens. Now just now you can understand why I'm saying, I use only question mark. So null error. The worst thing that happened is that thing won't run, but not crash, not error. Just as a reminder, you see I write if isn't null so run the next line like this. But why bothering ourselves? Instead of this if, just put a simple question mark. It's better. Until here we learn so many things and I hope you understand why question mark and what happens if it's null and the other thing, we continue in next video, so you have this video completely for this subject. 62. Day 9: Checking the user's guess Part4: Checking the user's guess part four. Let's continue. We continue and uncomment this, and of course, uncomment this change this back as well. I binding. And of course, question mark. We have this error. We click here. Go back. We don't have any error and read the studio bug. We talk about all of this. Let's go down. We have this check guess and inside here, we want to remove this as well and this part, we have this binding that we say inside that view. We need text result. What do you want to do? With text result, text, I want the text equals, sorry, I should put this question mark in here as well. At the end shift and the button next to the inter. I want to inter text. As I say, your guess is true. When these things happen, when your guess is equal to random number. You, you win. I can just say do win, for example, or not, your guess is true. Let's fix the warning as well. We click on this light but, and as you know, we can say press this if we say so, studio doesn't care about this warning. Sometimes and studio gives us warning, but we don't want to change that part. Maybe it's because it's an error. It's a mistake or any other take or only And with the studio bike. If we say to press. So don't care about that. You see, I say press this and my underline yellow color is gone. Let me just comment this. I have this under yellow to say Yes, you have a problem in here. But if I say, let it go, say, Okay, I don't care about this one. But I want and really sudo care about my text. So I put it on strings. Anyway, we understand, what is ignoring thing as well. Now, Let's continue. Let's do this again. This time we old inter instead of to press, we do extract a string resource. So in Arabic as well, we check it. Now, our name. Of course, I press home and say STR under line. Why? Because I add SCR to all the strings name. And press. I check this Arabic as well, press k. Now, I have this g string from where, from resource, from string fuller, from my strings, of course, and this is my string name. STR, your guess is true. And of course, if I put my moe mouse on it, you can see the value. Your guess is true, and that's default. And the Arabic, your guess is true. You see? So I can check what is the default and what is arabic as well. I hope you understand all of these very well. Now, wait a second. What if it's not equal? So it isn't true. What should you do then? We say, It's equal or less or higher. So we say I if the first one isn't true, Now, check this if, if the first if isn't true, now, check, this if. If our random number is bigger than what the guess? If our random number is bigger than guess. Now we should do something. Of course, and one back in there. Now, what should we do then? We say just control C this one and control in here. I just came in here and I'm not going to remove all of this and start type string. I just select this part and say, I can start typing or remove first and say greater. Then Andrew this studio just saying, I don't know any greater then. You don't have that string. Of course, I'm on this and then I press all in here and I say, create this string for me. I click on it. Now, new string value resource. Also Arabic as well, I check it. I'm just write in here. Anything you want, you can write. But I'm saying number is greater than your guess, and I put a dot to be nicer, or even I can make this n bigger capital n. It's up to you. So I press. And I have a CR greater than as well. Let me just check a string, a CR greater than, I have it, and a CR Arabic number is greater than I have it as well. Let me just close and close as well and minimize. So I create this one as well. What e? This wasn't true as well. I say E. Let me just check it again. Random number is less than. You see this less than you have it on your keyboard. If you press shift and the button next to M. And the other one on top is just the button after that. Not just next to M, press shift and two button to the right next to M. You can write this one. Let me just continue. Before I continue writing, I see this yellow line. What does it say? Let me check. I say condition random number lower than gues is always true. Why? You see you have three situation, three options. You're either equal Yes, I have equal. You greater than or lower than. So you check, it's not equal. You check, it's not greater than. So it's lower than even if you don't write this part, when it's lower then, you reach this if. So if you write this this if or not, there's no difference. So we can simply delete it, and Andre studio also says it's always true. If anyone reaches here, pass these two. It's true because it's not equal, it's not greater so it's lower than you can remove it and it's still ok. And I also has another warning. I put my mouse on it. It says else has empty body. What does this mean? Means you have nothing in here. It doesn't start you. It's not an error, but it says, it's better you write something in here. But if you doesn't write anything in here, there's no difference between these things be here or not. Let me just continue. And we just copy that line. We just paste it. Finding the series of text greater than it's just control C and control and less than less than. Okay. Now, we also doesn't have this. If I put my mouse on it, it also gives me this option. Create a string value resource for this. I can click on this like this. It's the same value arabic, of course. Well, I can just write number is less than your guess and dot. So I just press ok. The error is a still there because ID, click here, click back. It's gone. And it's okay now. Let me just run my game to see what just happened. What did we do? Let me minimize this and go to the game. Now, I have first number, I say 30, and second number, I say 40, start the game. I have a number between these two. My guess? What is my guess? I don't put anything. I leave it blank. Please go. Please inter your guess, I have, I have error that shows me I should put something inside. So I say let me just say 35 to see what's happened. Number is greater than your guess. So let's go up. How about we go up than 40 41, for example. Is it good? Go. Number is less than your guess. Of course, because maximum is 40. 35 and 40, 37. How about that? Go. Number is greater than. 39, 39. How about that? Number is less. Seven, 39, it's 38. 38. Good game. And if I say go, your guess is true. It is number 38. Good game, good job. We write our code and is just great and works, and also we learn many other things as well. I think I can teach you one more thing in this few parts. Take user guess. These are all the important things that we somehow should learn. Anyway, this is my logging technique. I just show you in here. You see how can we write our log, just like this, Control C, I just copy this. I have this check gues. This thing is very useful in big programs. I change it to guess and log import class. S. Now, if guess is true, I just want to say, first thing I change this tack. For example, to s one. I sometimes put a number at the end, so it's not complicated and doesn't get lost with the other things inside the Android. So I put it guess one. You see, we have, for example, game activity, line 40, that we change to 87 and say guess is true g equals guess to a string, And then I write again, just copy this random number is s random number quest string. Do you see what am I doing here? Let me just in there. So I want to check, if any time we came inside this eve, I have some data. I want to check my important data. As I say, in big programs, I check the problems and other things like this. Anyway, the line, and after that, and before that, I game activity, of course, name. O T cutlin file lame, and then user guess it true. This is the part that this thing happens, and then I say, Okay, the guess variable. First, I write the guess, and then I write, this is guess variable. And then I say and this variable. It's inside. This value is inside this variable name. Of course, I have to write that two string because in log, I have to convert this to string. These all are my message. Let me just copy this part. Control. I really like to teach you this as line 91. Guess Big this part is big and of course, guess is this and random number is this. We inside that check if we write this condition true or not. Because if we see my random number is lower than guess inside this, we understand that somewhere we write something wrong. Anyway. Inter control we again, user guess is low, and of course, guess is this, random number is this. You see how good is it? I can even write a variable name number or number of guesses globally and add it before Or before this guess. In here, I can add it this is first input, second input, third input, and all the other data that I need. Then I run my program, let me just show you that as well. C. Let's run. Let me just go to game and, of course, clear, and control, we check the guess, and of course, minimize this. I want to play a game. 20-30 and start, your guess. My guess is 25, go. Minimize this and zoom in twice the number is less than your guess. Then 22, how about that? Go my guess is t. What if I say 21, go and then 22, go. Okay. Now, let me just check Log cat. This is my guess phone logs and dates Our minutes, seconds and even smaller than that. So game activity, my first action in that time is game activity, line 87. User guess is low. Oh, I think I write something wrong. I should change the line number. 87. Yes. Sorry about that. I should change these 295. But you see the point. Anyway, user guess is low. Guess is 25. But random number is 22. C guess is 25. So I try again. I say, guess 22. Random number is 22. Now, where were we, we are in user guess is true. Why? Because we should be inside that if guess 22, random number 22. Anyway, I say, Random number is 22, guess, I guess 21. Guess is bigger then. I even write this rang as well. Input. I think I write it opposite. Anyway. But I show you the point. I check it out as well. I do this like this. Is it very okay and then because it's 22 and 22. Let me just clear this. And stop this as well and minimize. In here is low because my guess is low and here is peak. What about if I write this one wrong, for example, opposite. When I run the app, I check it out and see, my guess is, for example, 50, my random number. Is 20 and I say greater then. I think it's wrong, and then I came in here because I see my variable, I say, it's wrong, I came here and understand, this part, I write this part wrong. Just like this, check our bigger programs to see where and what is wrong. Now, if I run the up again, Now, I win the game again. Now let me just the. This is my log. Now, I came in here in line 97. My guess is low. Why? Because my guess is 35, random number is 37. I guess again, my guess is 39, random number is 37. Because of that, my guess is big. And then I changed this 39 to 38, is big, and then seven, is it seven? Yes, it's 37. It's two. Now, as I say, this kind of like this of writing is when you have a big program, you can't find where is the problem. I write many places just like this and don't forget. Don't write it in the places that you don't need it. You see if you, for example, write it in here in here. The places that you don't need it, you just waste your like place. For example, you can do it with 100 like, but you write 500. And you waste a lot of your time to find them. For example, in here, it's a simple code. We show error. Why should I write any like in here? It's not reasonable. But in the places that we have complicated situation, and I need to see different variables side by side and just a specific thing. Sometimes I use just like that. Of course, there's other ways as well. We talk about these ways in the future. But I think it's good to understand we have this way as well. It's a really simple way, as you can see. Even we don't have to use a complicated and ready studio tool. It's a simple way and it can be used side by side with other ways that we're going to learn in the future. I think we can close this taking guess part and I comment this and I put them inside the code, so you can see how is them and if you write anything with mistake, you can see them in here. Thank you. 63. Day 10: Report Button Part 1: Report button, part one. So we reach the report button to show this report. Where were we? We want to show our report inside this text view. But first, before this text view, let me just talk about this gravity. First, I should change this wrap content to match patent like this. So I have the whole area. Now I can show you different gravities. For example, write, we be like this on the right, or Left like this on the left. You see the difference? How about a start and end? Let me just see. I have different things a start. A start means left on English because English writes from left to right. So a start in English is left. About end. Let me just check means right in English. Because as I say, in English, we write from left to right, so our end is right. But if we change our language, for example, in Arabic, we write from right to left. And then the end in Arabic means left because from right to left and end means left in Arabic. Exactly because of that, we use this end to end up, a start to sort of. These things in different languages based on from left to right or right to left can be different. But for now, let me just don't talk about this constraint end to end and other things and just talk about this gravity. So let me just say we have this in start and a little zoom out. So we should change our view direction. So we go up in here and we write DR direction, we change layout direction. It is right to left now. You see the difference. Which part is different. You see this result at the bottom. Let me just zoom Zoom zoom a little more. Okay, this result, you see at the moment, my results on the right why because my layout direction is from right to left. And the other things based on that, here are different now. But I don't want to show you that. I want to show you other things. So I just press inter and say, again, direction. Sorry, I should mention that if you just use this direction, layout direction, you see that this text direction has no difference, and you might get confused because this layout direction is for our layout. You see how layout is changed, but you want to change your text direction so this text can be affected. So I write again the IR direction text direction from right to left. So my text direction inside this constraint layout is now from right to left like Arabic. So if I say this text view, gravity is a start. What does a start mean? A start means the place that you start writing. So I write from right to left. So my start is right now. Let me just change it again. Okay, we have right to left. Let me just say left to right, LTR means left to right, RTL means right to left. So left to right, you see the result goes back at the bottom, this one. So now the text left to right, like English, left to right, left to right. Now, my texts come to the left. Why? Because it's from left to right, and I say, I want to start if I say, and as you can guess, it goes to the right. So if I want to write, for example, for this text you margin. Let me just write margin margin. Margin, what I want margin for my we, for example. This one, margin right. How much? For example, ten DP. I have margin right, ten DPI. I have earning. I have recommendation that it's better to write margin end. Why margin end? Why does Andrew de Studio said it's better to write margin instead of margin right. You see, my right is my end now. My right in here is equal to my end because it's left to right. Let me just show you left to right. So it says, right end instead of right. Why? You can understand it now because when you change your language, if you write, when you change your language in Arabic, write becomes left. But if you write this we, when you change your language, there is no difference in this, no difference at all. Because of that Andrew S says it's equal to say, and it's better because if you change your language, it changes the end change. So I think I talk about this enough as well, and I just remove this. I think you understand about fixing these problems in different languages. My directions shouldn't be fixed. It should be different in different language based on left and right in that language. And I think you understand the meaning of this end to end and a start to a start. This is different in different languages. And you see we're at and now, yes. And if I say wrap content at the start of video, there is no different. Why? Because it's fixed. There's no left or right. There is no space to move. Because of that, I change it to match pattern, so I can show you what's the difference. And, of course, I go up and remove these two. Okay, we remove this. And at the bottom, this gravity because it do nothing because of that disrupt content, we can simply remove this as well and remove these spaces. And this look there is no extra space and entering here. So let's go to our game activity to continue coding. So we want to write code. And if we click on this report, when we click on this report, this should be on height. It should not be hidden anymore. This visibility shouldn't be gone. So let me just go here. Oh, in It listener, we have this innit listener and we have our clicks BTN start and BTN go. You can just minimize this and minimize this as well and press enter in here, say BTN report our third button, and press dot and set and click listener. Inter. So what do we want to change? We want card report. Card report, check the name. This is our material card view. We don't want this. We want the ID. This is the name Card report. So I just control C or simply I can write card report or just paste that Card report. This card report, we just say visibility is gone, is hidden. This is hidden. Now I want to change it. When this button is pressed, I want to visibility be changed. I press dot my visibility, just write V and I press Center on visibility. The first thing equals view dot visible, remember, not a small V. You should write big V, view dot visible. What if I forgot? Imagine I forgot to write capital. I write a small. What just happens? Let me just show you. I have error. So don't remember you should use capital V. This language is case sensitive. View like this with capital V and visible. Now, what do we want to do? In these two or three video, I think we make it three video. We want to save the things that user inputs in gas inside our variable, somewhere, not even a variable. We want to save it somewhere in this case, inside our variable. And after that, when user press report, we show that data inside report. So we want to save this value somewhere. What can we use? Do you remember we have these variables. Just like this, we save data inside this variable. I think we should add range as well. Let me just add the range as well. Inside here in here, I should press Inter and say mean equals, for example, zero, and max is equals, that is zero as well. So we have this amin and MC and we came down in here get random number. We have this r. We remove this varmin and Varmax. So we have min and max. Why? Because we want to check that the user not go out of that range. So we create this varmin and max globally, and down here, let me see down here, we say Min and Max have their value. And when we want to check guess in here in first I before that, I write if my guess is bigger than Max or I press Shift and I press this packet slash between my packet space and inter in my keyboard. You see if I don't press Shift, it's like this. This. But if I write shift, it's like this. Because I want to write or, I say two of this. Two of this means or. You write this or let me just remove this. As I said, I guess is bigger than max, and also guess is less than men. What should I do? I want to tell you and of course, enter in here and one else in here. And press delete, delete, and not delete, press shift and now delete. Stop. I have my Ls E. So as I say, if this happens, I should just say binding dot EDT yes, mark, D let me just show error. What is the error? Or I just write, copy this and in here paste this string. What a string that a string, SR SR we say out of range, out of range. I said, I have this? No, I'm not, so it gives me error that I don't have this. So I just create this string value. We just pause the previous teaching because I want to add this. It's just take a few minutes. So, what should we write? Just press Arabic as well, and what should we write? Write your number is out of range. Just like that. And press Okay. Oh, I just run my app and press game, and I have, for example, 5,000 start the game. My guess my guess is five, it's out of range. Press go, it's out of range. If I say 5,000 something out of range, but 55 50-100, it's good. You see? So my user can't write out of range values. I just want to add this as well. So I'm just saying I want a variable that keeps my guest values. So in here, I press Inter and say Why report, I think is a good name report. As you know, we can just say it's int with Big, it's int and say it's null. Just the place we declare and create this variable. Because if we don't write this null, it says, you can't leave it, you should give it something. And even if I say for now, give this null. I also says it's non null type. You can't give it null. Because of that, we just say question mark. So it's nullable now and we can give it null. Or simply we can give this a value, for example, zero or minus one. No difference. And since we have the int and we give this a value, we don't need this int anymore because the Android Studio, the Cartlin language itself give this report, the int type. So it makes some problems, but for now, let me just continue this. And go to PTNg Where is RBTNo? This is RBTNg and stay in here, press inter. I want this number. Control C in here. Sorry, inside my report. My report is equals this. So until now, we save this value inside our edited guess. Which one? This edited guess inside our report. So it's enough for this video, we continue in next part. So our video doesn't get too long. 64. Day 10: Report Button Part 2: Report button, part two. Let's continue. We reach this part and I just write the comment and say to do. You see, it's just like a normal comment. Why? Because I put one space between them. Like normal to do writing, if you write to do, it's nothing, it's just a to do. It's just a simple text. But if you remove this space like this, press built, it's different. You see this a different color. Why? Because I write this to remind me I should came back here later. Let me just see what did we do in previous session? I write my Edit guess value inside my report variable. So I can show it when the press report button. But when we were going to do this, I just remember I didn't add this range. So in previous session, I add this if as well. I say, Okay, I have max. I have mean. What is my meant max? My first value, my second value is my range. So I want to say, my guess should be between my mean and my max. So I say I my guess is bigger than max, it's wrong. 00 means even if one of these is true, go to the IO my guess lower than me. So for example, if I say 50-100, if I write five, of course, it's not pier than 100, but this one is true. Even if one of them is true, when you say, so I became true and my I runs from here to here runs and my Edit guess, error became this text and none of the rest check. Why? Because if this if isn't true, the rest of these checks because of this. I think I say these things a little fast and I should explain them better. So let me see what else? What else? This O? How can I write this or? You see, let me just add some space. So I have this button between my inter and packet space. If I write it, it's look like this. You see this look like this. But if I press Shift, if it has a straight line like a column upper than this sign. So if I press shift on my keyboard and activate second character in this key, press shift and press this again. So I have this. But if I not press the shift, it's just looks like this. So I press Shift and it's okay. So let me just select this like this. Okay, delete. So I press Shift and one, two. This means. So O, this O. This is true. Our condition is true. And even if both of them true, also our condition is true. The only situation that our if isn't run is when this is false, and this is false, as well. Only in that case, our is false and our I isn't run this part. So let me just remove this. I think I explained better this time. I hope you understand. And the variable, let me just show you the variable. You see this max, you see this mean. We define them in here so we can globally access them. Before that, we only have them in here locally. So outside of this, we can't access them. Because of that, I add that on the top and remove that arb before them. So these are global now, anyway, since we came back to this go button and checking this box, let me just add one more thing to make it more beautiful. Better. What should we do? So if you there put the right number, correct gas, I think it's better to, for example, killing this, killing this, killing this, or even hide this button, go button. You know what I mean? Make it better game. So let me just go to code and find my buttons. So in here, we and go. So in here, I just press Inter and start writing. You see, we have this to do. Why? Because we want to continue our report button. But first, we make a few lines to make our game better in this part of video, and then we came back to this report. So it's really common when you want to live apart and later on came back, you write to do. So in input layout guesses, write dot dot what visibility. Okay, what do you want to do with this visibility? I want to say equals V with capital V. Do you remember if you write lower case, it gives you error. Okay, what do you want? I want god, hide this. So when do you want to do this? When my answer is correct? So, when this answer is correct. Here, this I is when our answer is correct. Let me just copy the whole part. So in here, press inter and control V and and enter and close this. So when my guess is right, height this, but it doesn't know. Guess. Why? Because it's the variable we have in here. So what should I do? Let me just think about it. But let me see. Isn't my guess? Is this? Yes, it is my guess. So this is my function. So what is my guess? This is my function. I call my function in here. So this is value I pass into my function. So this is the guess. Edit guess, I take that text, that sing to end. This text is the value of IDT guess. This is my guess. So I can simply just control, see the whole thing and double click in here, you see double clicking here and control it. So this is my guess when my guess is equal to random number, so make it invisible. And as we can understand, we can just write this in here down here, but let me just continue like this. You can do this in both ways, but I just want to do this in here. I'm not going too fast like previous video. Let me review this. This is my object, Edit guess, that text, it means the text inside the value of the text of that object. So what should I do with this text? You should make it a string, convert this text to a string and then make it int. Why? Because you can convert to int and then check it with random number. Why? Because this random number is int. So you can't check it with a string. First, you should make it int. Anyway, then inside out, if we make it visibility gone first inter, so what else? Just I press Control D two, duplicate this. Let me just do this again to remove the line. Click in here anywhere here, here, and press Control and D. You have two of these. Why do I have two of these? Because you see Input layout guess. This is our input layout guess. The whole part. We have this button as well. So we know our BTNg name or not. If not, click on that and see TNG. If you do just came back and change this part to PT N. You have three PTN. PTN go and make it invisible. Let me see what else do I say? I say, Hi, this, hi this and clear clear this, this, this. Let me just came back and next line, I have Edit. I have Edit, first input, first value, right? First value. Most of the time I write input. It's okay. I'm not. I sometimes make mistakes. Dot that's what that text. So what should I do with that text? I just say dot C Killer. Clear that thing. And sometimes I by mistake, low the line like C sharp because I write other languages as well. If you see I do this thing, for example, in previous video, it's okay. It's my mistake. Just remove this because in cart you don't have allows line like this. Just remove it. Anyway, what do I have? It's maybe your text is null. Okay, maybe it's null. So Question mark. If it's null, it's okay. If it's not null, then clear that. So, is it all? No, of course not. You just do for Edit first value, press Control and click on it. See, Edit first value. What about the rest? Oh, you have second number, second, and guess. So we have two more. Let me just came back and click in here and press Control D. It's so easy. So one more Control D. So I have two copy of that. So I just change this part, select this part, remove it and control a space second value. And of course, select this part, remove this control space. I have the guess as well. So clear all of them. You see, I can just go to them and double click on the name and Control C, copy and paste. But I want to show you different ways, for example, with these controllers space things. Before continue with this to do, let me just run the app to see what just happened. My application runs and again Okay, my first number is, for example, 15 and second number is 20 start. My guess is 25, it's out of range. Go. Let me just see your number is out of range, of course. What about if I say two Go. It's still out of range. Look, if I say 16, greater than 17, greater than 18, greater than how a 19, still greater than how about 20. Your guess is true, and you see where is the Gb ten? It's gone. Where is the guess? It's gone. Why? Because we write PTNO and input layout guess. When we are right and our guess is true, they should not be visible anymore. And, of course, you see this box and this box is clear now. And if I write 15 and 55 and say start, your guess is empty. Exactly because of that, I clear that as well. So I just want to this looks better. And as I mentioned, it's not right to write extra if when you can do this with that other I. So it's better to write those codes just down here, not in here, but just write in here. To show you, you can write it here as well. But as I say, it's more perfessional to write it down there with the other I. And even we can even more perfessional, it's better to create a function for this killer thing. Killer, killer, Killer, invisible, invisible, clear of all of this and something like reset all of those datas. So it's better even have a function for that. Anyway, we don't do this anymore, and let's continue our report button. So we just want to continue this. Our problem as we just talked about, is this when we save our number, our guess inside our report, just last guess goes to this report. Let me show you. Let me just continue and show you what is the problem. This is the report, and this report is a int. I just can't take one number. So we have this report, and we want this text view to be duplicated. So just this control C, press inter and control. Simply just I remove this label from the ID. So I have another text view, but they're on top of each other. So let me just change this top to top of we have top to top of, remove this part as top to top of and say top to bottom of bottom of what. So from your top, just connect to the bottom of enter on that ID. And of course, this one, why is it so hard this one, this one. Like this. And remember, if I don't write this part, for example, let me just select this Control X. If I don't write this part, it's wrong. I should write this ID part before that, just like that, and just like this. And especially at sign Pallas, Idah the whole thing. It's the rule, it's the law. So let me just make it match parent. And I think it's enough. Let me just continue this discording in next video. So our video isn't became too long. 65. Day 10: Report Button Part 3: Report button part three. Let's continue. Okay, we save our edited guess inside our report variable, and we say it just take one number, not a series of guesses. So let me just remove this to continue this report part when BTN report clicked in here, set on click listener in here. So I say TXT report dot text is equals to what the thing that we already save this report, you see this report, we already create and in here, we give data inside that we put it inside dotty report dot text, but there's a problem. This report is number, it's in so I should change it because this text is a string. I just press that string. As I say, if I by mistake, close the lines like ChR, you just fill in this. Why? Because sometimes because I write CSR programs as well, I write this by mistake. Let me just run the app and see the problem. And then came back to fix that. So let me just minimize this, go to game, and say 15-20 and start and my guess is, is it 15? Let me just go down, go. Yes, it's true. Okay, I can show you. It's okay. Let's start again. Sometimes happens, it's 15, it's really 15. Okay. Let me start again and minimize this. My guess is again, 15. Go. Okay, thank God. 16. Okay, my guess is through. So 15 and 16, I enter two numbers. This time is 16. So let me just see the report, click on this and my report is 16. But wait a minute. I just enter 15 and then 16. I should see two numbers inside this. But I only see one number. What should I do? So this is our problem. Because it's my last guess. So actually, it's the result because my last guess is the result. So let me just stop this up and minimize this. So my problem is this report can only hold one value at the same time. Even this or even this can all of them have only one value? What's the solution. The solution is array. Array is a series of the same variable. So it can have many spaces. Let me just say imagine this var variable as a box, array is a serious boxes. For example, imagine if your array has ten slots, you can put ten different numbers inside that and the don't do anything with each other. Not just like this only one number. Many different values. Where can we use? For example, in here, we want many different values for report. User make ten guesses. We want all the ten numbers in that series. Or for example, in a classroom, you have ten students and you have the variable name. You don't want one name. You have the five, ten, 20 students name. And you want them all, not just one of them. You use array and many, many other places. For example, in tables, you have many slots, and inside those tables, you use one. Variable slot for each table value. For example, if you have ten row, you use ten different slots for that Before I change it to array, let me just give you a few more things. First, one more example, for example, when you buy a few things in a store and you get receipd, we can use array in that case as well. Arrays can use many items that you purchase on one variable. And then you can add each of them together to have total price and many other examples and one more thing, I forgot. Inside this text view, you see, I have this text. I shouldn't have this text in here. If you click report, you might see this report. So what should I do to see how big or small my text might be? I should change it to tools. I just forgot that and we change it. So when I run my app, I won't see this text, but in here, I can see the size. This is a little important and make it really nicer. And helps me to find it. Imagine I'm somewhere else and I want to click on it. If this doesn't have any text, it's harder to find it. But when it does have a text, I simply click on it and it selects in here and I can change it. Let me just show you that as well. Select this control X. You see, I don't have it. It's gone. But if you have this you can't find it. Now, even if you're on somewhere else, you can find it more easily. So let's just back to our array. We have another way. What? We can make many reports. Like what? Control DD, for example, report, report two, report three. But there's a problem. What if my user gets 50 number? Can you imagine we add 50 report and inside our code, we give these reports one by one, their values. No, we can't do this. Of course, it's just three. I mean, just let me show you control, d d d d d. Many more. You can't do this. So just remove this. This is not okay. Instead of this, we use RA. This is a better example after. Even in that shop, we just write a program for that. When, customer brings 20 items and you want to add them, you can't create 20 different value and 20 different variable. Why? Because what if customer brings 50 items in their basket? What do you want to do then? You can't. Let me just remove this and go here to say this report is, what is it? A list of a list of I want this. Let me just show you again, clear this. If you press Inter and have something like this, if you in here, press control space, you have nothing. None of them is useful. Just came back one character in here. In here, press control space. It gives you two options. You want the second one. Why? Because I want to say it's in with Big I, as I say, if you write a small I, you have error, capital I, it's case sensitive anyway. Let me just comment this and in next slide, write it like this. A port. What is the type? Instead of say equals of, what is the type? You see in here, we say it's equals of this. But no, no, wait. We give the type in here. We say, y. I just want to write this for you. List. List of what? List of Bullion, a string or It give the value.This report is array list of int because it's integer. You see can have many different things. For example, if I remove this and say just string, you can have many different string inside your report. But I want integer. And remember, these are important tips. When you say it's int, all the arrays, spaces, all of those sections, boxes or whatever you want to say and learn by that, all of them are the same type. So all of them at the moment are int. You can put a string inside them. Why? Because all of the report sections, parts, all of them are ins and can have only the numbers, not even the decimal. All of them are integers. So we have error. What should we do? We should give this value. We should initialize this. Or let me just create this for the first time. It's not B null. I say equals. Let me just write in here equals, I have arrow array list, and just like this. What do I have? I have error. What should I do? Let me just go in here and space. Let me just show you. You don't have error now, but if you forgot to press space in here, your IDE things these two are one. These two are together and doesn't think this as a equal sign, but makes them together. For that, I just press this space. To say it's separate, separate this is with this part. These are separate. If you forgot this space, that happens sometimes you have error. Anyway, this is another way that I create this report as an array. But the most common way is just like this, you see, is shorter and more simple. I have this report. What is it? Array list of int. I can create that with very, very long code, even longer than this, it's okay, but why should I? I make it with simpler code. And since I should tell you some different things, I try to give you more examples. Even just like this, you remember these tools. I try to give you as much as I can from my knowledge. So you can learn the best way I can. I hope you not bored because I try to teach you many different tips and things. Anyway, let me just show you this. I can comment this again, control the in here and remove this part and say, No, I don't want to give this anything. So what you we do I want to give this null, but you can't because it can't have null. It's okay. It can have. So it can have null, and I should give this value in the future. I just want to show you this can work as well. And in here, if I remove this space, it gives me y because we don't have greater than question mark. Do you remember we have greater and equal. But since we don't have great question mark, it doesn't get confused. Anyway, all the time, it's better that you have your space. So even the IDE can understand, you don't get confused. So when I want to give this a value, what should I do? Simply in here or in here or in here, I should say, okay, for example, in here, I just press inter in here and write report, it equals array list and we give this a value, it's not null anymore. It doesn't have any number inside, but it's not null. And one more example, if I say int, it's grave, why? Because I say it's int already. So I don't have to tell this again. So I don't have to use that int. Anyway, I just remove this part and remove the extra inters and say, before I forgot, the A A, small A. Why? Because it's case sensitive. When I want to give this a value like this, arraylist of it's with a small A. But if I want to say arrays, it's with A. Again, arrays, A, list A, a list of small A. If you, for example, in here, write a small A, you don't have that error. So it's case sensitive and don't forget these things. I just comment this an uncommon this list of int. I think it's easier. We can use the other thing, but I think it's easier and better. Let me just continue this in next video so it's not too long, not became too long. 66. Day 10: Report Button Part 4: Report button, part four. Let's continue. So we have error. What is our error? You see we just create our array and we have error. This report is an array list of int. But we have error. What is our error? We can put the value inside this report like this. So what should we do? We can say, first set this Control X, cut this, remove this, remove this. Okay? Now, Dt. Dot add to add what add this in. This value add this with this ard to this array. Give a new place of this array to this value. We can use this art when we have array so I have this arrays. So I can use this at. Let me just check to be sure. Do I have any non arrays? Yes, I have mean, I have max. Let me just use this mean. Control C, I write this mean. For example, even in here, inter mean dot at Oh, I don't have any at. You see? Why? Because that's not an array or even in here side by side. Mean that I want to write at just like that at, no at. Why? Because mean nuts an array. I should give the mean value like this. Mean equals to, but no at. Remove this and extra in. Let me just run the game. Run to minimize this and click game. I want from, for example, 15 to 20 and the start guess 15, go. Great hair, 19, go. Less 18, go. Less about 17. Go. True. Now, show me the report. Let me just zoom this. You see you have this array 151-918-7017. I have 15 1918 17. I don't have just the last number. I have the whole. So even if I enter 100 different numbers, I can have my history and my report until now, can work like this. It's not so pretty, right? You see we just say Tix report, dot text is equal. Report dowsing. So the whole variable, the whole array, we put that inside that Tiki report. Of course, it's not nice and it's not a best way to do this, but it works. And I didn't change it so you can see what's inside your array. Of course, in future videos, we make it paper. Don't worry. Just focus and learn all of these things. These are really important things. We're not in very beginner, but still they are really important. Since our game can show the report, even like this, I think it's enough for this video, and I think we save very important tips. For example, one of the most important things is we should initialize our variable. This array should be initialized. For example, let me just do that one more time. If I say, let me just say A. What is it? I array list of integer. Yes, and press N, press inter. I say a dots at, for example, four, and if I say, what's the error, it said property must be initialized. Exactly because of these things, you see in this example, report array list, int, we initialize this like this equals array list. Or in here, we say our report equals array list of Int. In all of them, we initialize it. And if we want to say it's null, we should initialize it later. So we talk about this initializing in different ways, and already you know about this null. So I think you now understand if we say null, so later, we should initialize and make it to have a place on the computer or phone ram. The phone is a kind of computer, it's a computer. Anyway, on the device AM. I should have a space for itself initialized. It's for to have a space on the device AM for this variable allocate space for that. L, what happens if I press inter and say, A equals? Oh, I say, in global place, let me just cut that. I should move it to, for example, in here, inter, and here inside is create. That's the place to create a variable for these kind of tests. Anyway, A array list, so if I don't write this, I just have this small error now. Variable A must be initialized, of course, as we talk about, and then I say, A equals array list of and then my error is gone. So I just initialize it. Why it's fixed because it allocates this A a place on the RAMs device. No, sorry, on devices RAM. Yes. On the devices RAM. What if we just do this, this part, Control X and remove this in here, control we just do this in here. It says, please tell me what does this variable type? I say, it is integer. Now, it's fixed. It's just like the way we do something equals a list of int and you see the difference of colors. TA is white. It's not allow boot. These are global have different colors. You click on it and click in here, it colors change. Sometimes I have this kind of box you see, click click. Sometimes these things happens. Small errors, small bugs. It's okay. Android Studio updates and many of these things fix by itself. Maybe want to know you can change all of these colors in setting of Android Studio, but please don't change many things or try to not change anything in setting until you learn a little bit more. And if you want to change, just change the thing you have to. When you learn more, you can make it more personal just for you make it better. But now, you might make something change and it doesn't work as well. You might broke it. I shouldn't say broke it. You shouldn't change it a lot unless you learn the setting of this Android studio. Can I add any other thing? Yes, of course, Control, for example, at six, I add two things. And even can I say this is Val? Does this give me a error Val. You see? It's okay. No error. I think I say even more than enough and let me just delete this and it's enough. It's enough for this video.