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A Step –by-Step Guide to Android App Development in Kotlin Welcome to creating your first Android App in Kotlin. Google's announcement that Kotlin is now an officially supported language, is exciting news and is really the future of Custom Android app development. I highly recommend that anyone learning Android app development for the first time, start off with Kotlin. And then, write your very first Android app in Kotlin. We will walk through the basic components of an Android app and how the different parts work together. I love writing about Android apps and can't wait to show you around. So, let's get started. What you should know You don't need any Android experience to develop this, but basic programming knowledge helps. We will be using a Mac in this post. You can use Windows or Linux as well. There will be very slight differences which we will try to point out during the post. We will download Android Studio together and then we will walk you through the setup. Why Kotlin? Traditionally, Android apps are written in Java. Recently, Google has announced official support for Kotlin, a modern programming language that is compatible with Java. Why choose Kotlin? It's a really great programming language. Compared to Java, it is much more concise and it has a stronger null safety, meaning that you can catch potential crashes much earlier in your custom Android app development cycle. For me, Kotlin has been amazing because it has a lot of built-in functionalities that you would have to implement yourself in Java. Very often I can replace 10 lines of Java code with a single line in Kotlin, making development faster and less error-prone. The Android community has been very excited about Kotlin for a few years, and now, with the official commitment from Google people are moving from Java to Kotlin to write Android apps. I believe that Android will move quickly to Kotlin. So, if this is your first time writing an Android app, Kotlin is the way to go. All right, let's get started. Download

The first thing we will do, is to download Android Studio, the official IDE for Android. IDE stands for Integrated Development Environment and this is the editor we will be using to write our Android app. To get started with the project, we will download Android Studio. Open your web browser. Search for Android Studio. Let’s go to Android Studio starts to support Kotlin natively from version three and above. After that, click on preview, and download. Accept the terms and conditions. When it is done downloading, open the zip file. On the Mac, double click on it to extract it. Right now it is in the download folder, usually. I like to put it in the applications folder so I know where to find it next time I want to write an Android app. It is up to you where you want to put Android Studio. Now that we have Android Studio, let's open it. Choose open. If nothing happens, you may want to switch windows to make sure that it is not hiding behind the browser. There are two choices when you first open Android Studio, since it is the first time that we're using it we don't have any settings to import, so select 'Do not import settings.' Welcome to Android Studio, press next. We will choose the standard installation. Android studio will then download the list of things that you need you will need, you can see it here. For example, the emulator, the SDK, the support repository etc and click finish. Downloading may take a while, so make sure you set aside a lot of time when you try to install Android Studio for the first time. During the installation Android Studio may ask for your password so that it can install other components go ahead and type that in. Alright, it finished, so let's click finish to close the dialog. Next we are going to start, a new Android Studio project. Start a new project Let's write an Android app. In Android Studio when you open it, you will see a list of options, hover your mouse over 'Start a new Android project' and click on it. When we create an Android project, we will need a few parameters, first a name, let's call it Hello World. Next, it asks for your company domain. The reason why it does that, is because eventually when you publish your app on the App Store, the domain is going to be used to generate the package name and it have to be unique. The convention is to use a domain that you own so that it will not clash with other apps. Next is project location. The default value is fine, as long as you remember what it is, so that you can go

look for it later. On the fourth line you see package name, it is taken from the company domain and also the application name, Android Studio also generates it for you. If you want, you can click on edit to give it another name but I'll just accept this default value. Finally, very important, make sure you click on 'Include Kotlin support' so that when Android Studio generates the project, it is going to be using Kotlin instead of Java, click on next. Here, Android Studio asks us what target we want for our app. You can see that it says "By targeting API 15 and later, "your app will run on approximately 100% of devices." Click on 'Help me choose' for more information. Android Studio has a very convenient guide. What this means is that, as you choose a higher and higher level you have more and more functionalities that you can use, but you can support fewer and fewer devices because fewer people will be running devices with the latest version. Which version to choose? It really depends on what you want your app to do. You will need to review the list of features that you need and then decide how many people you want to support. For our first app, we will choose the lowest version 15, click okay and then, press next. Now Android Studio asks us if we want to add an activity. The default is fine, meaning choose empty activity, click next. And now, we want to give a name to the activity and the layout name. You can just leave it as is, using the default values main activity and activity_main. Press next, and we are done, press finish. Now we can see that Android Studio is opened with the project that we just generated, click close to dismiss the tip of the day. First thing I recommend you to do, is to go to the drop down on the top left corner, instead of Android view, choose project view. This means that Android Studio will display the folders and files in the same way that it is on the disk. This makes it easier when you want to store them in a version control system or simply to find out where the files are. Next, we are going to create an emulator and then run this app. Run on the emulator To run this Android app, we will need either an emulator or a device. Let's create an emulator. Go to the toolbar on top, and look for this icon with the little Android on the corner and the rectangle that's purple inside. This is the AVD manager or the Android Virtual Device. Click on it. It will ask you to create a virtual device. Click on that button. We're given a lot of choices. Here, we have a list of devices.

As you develop your app, you may want to create multiple emulators so you can check how your app behaves. For us right now, the default one is just fine. So we'll pick Nexus 5X. Click next. Once you pick the device, you will also need to pick the system image. System image means that we may want to load different versions of Android on this emulator. Under the recommended tab, you can see O which is API level 26 or Nougat which is level 24. In general, I will recommend using the latest version. So go ahead and download O. Accept the license agreement. When it is done, click finish. Now that it's downloaded, we can use it in our emulator. Click next. Finally, give it a name. The default is fine, and then presses finish. Now that we have created an emulator, let's launch it. Click on the green triangle. It may take a little bit of time to launch the emulator, so please be patient. Now that the emulator is launched, we're going to move it to the right-hand side of the screen and then close the list of emulators. You may have to switch windows to bring back the emulator when you close the list of emulators. Great! The emulator is just like an Android device, except it runs on your computer instead of a physical device. Next, let's deploy our app. Click on Android Studio, and then on the top toolbar, you can see that there's a dropdown that says app. Next to it is a green triangle. Click on it to run the app. When you deploy your app, Android Studio is going to show you a list of connected devices. Here, you can see the emulator that we just created and launched. Select it, and press OK. Once again, switch windows so that you can bring up the emulator. Congratulations! Here is your first Android app.

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A step –by step guide to android app development in kotlin  
A step –by step guide to android app development in kotlin