How to write a app for Android yourself: from scratch to launch

Creating your own application for the most popular mobile operating system in the world seems like a complex process, accessible only to select programmers. However, modern tools and training resources have made the barrier to entry into development much lower. Even if you have never written a line of code, the logic of creating apps is subject to certain algorithms that can be mastered in a few months of hard practice.

In this article we will analyze the full development cycle: from the idea and choice of a programming language to compiling the finished product. You'll learn what tools you need to install, how Android development works, and where to start your first project. The main thing is the sequence of actions and understanding of the basic principles of the operating system.

Let's start by deciding on the direction. Application development is not only about writing code, but also about interface design, testing and optimization. Are you ready to dive into this fascinating world? Then let's start preparing your workplace.

Selecting a programming language and development environment

Before opening the code editor, you need to decide on the tool on which you will write your app. The Android ecosystem offers several options, but for beginners there are mainly two ways. The choice depends on your goals: whether you want to create native applications with maximum performance or cross-platform solutions.

The gold standard today is language Kotlin. It is officially supported by Google, has a concise syntax, and is fully compatible with Java. The second option is classic Java, which contains a huge amount of legacy code. For an absolute beginner, Kotlin will be preferable, since it requires less boilerplate code and protects against common errors.

⚠️ Attention: Google is gradually abandoning support for older versions of Java in favor of Kotlin. Starting with Java in 2026 only makes sense if you plan to maintain legacy enterprise projects.

You'll need an integrated development environment (IDE) to write code. The undisputed leader here is Android Studio. This is a powerful all-in-one tool that includes everything you need: a code editor, a device emulator, debugging tools and profilers. Installing this app is mandatory, as it will automatically install all the necessary components of the SDK (Software Development Kit).

Installing and configuring the working environment

The process of preparing a computer for development may seem lengthy, but it is critical for stable operation. You will need a computer with sufficient RAM (16 GB or more recommended) and free disk space, as emulator images take up a lot of space. After downloading the Android Studio installer, follow the installation wizard.

During the setup process, the environment will prompt you to download various components. Do not uncheck the items relating to Android SDK Platform and SDK Tools. It is these packages that contain the libraries necessary to compile your application for different versions of the operating system. Without them, it is impossible to write a working app.

Pay special attention to setting up the emulator. This is a virtual device that will run on your PC and simulate the operation of a real smartphone. You can select the model, screen resolution and Android version. To begin with, it is better to select an image with the latest stable version of the system in order to test the application under current conditions.

• 📱 Download the official Android Studio distribution from the developer's website.
• 💾 Allocate at least 20 GB of free space on the SSD disk for installation.
• ⚙️ In the SDK Manager settings, make sure that the latest version of the API is loaded.
• 🔌 Enable virtualization (VT-x/AMD-V) in the BIOS of your computer to work emulator.

After installation is complete, launch the environment and create an empty project. If you see a welcome window and buttons for creating a new project without errors, congratulations, the hardest part is over. Now you can move on to the structure of the future application.

Project structure and main files

When you create a new project in Android Studio, the system generates many files and folders. This can be intimidating for a beginner, but only a small part of it is really important. Understanding the project hierarchy is the key to successfully navigating your code. All files are logically divided into app code, resources and configuration.

The main code is located in the folder java (or kotlin). Classes that describe the logic of the application live here. The main file is usually called MainActivity. It is the one that is launched first when the user opens the app. Inside this file, you will write commands that force buttons to be pressed and data to be downloaded from the Internet.

The visual part of the application is stored in the folder res (resources). Here are screen layouts (layouts), pictures, lines of text and styles. Markup files have the extension .xml. Separating code and appearance is a fundamental principle of Android development, which makes it easier to maintain and change the design without the risk of breaking the logic.

File AndroidManifest.xml is the passport of your application. It contains the package name, version, necessary permissions (access to camera, Internet, geolocation) and a list of all activities. An error in this file may result in the application simply not being installed on the device or crashing when trying to access protected resources.

Creating the first interface (UI)

Application development begins with what the user sees on the screen. Android Studio has a visual Layout Editor that allows you to drag and drop elements with the mouse, but professionals prefer to write the layout code manually or use a modern tool Jetpack Compose. To start, we will consider the classic approach based on XML, since it is more visual for understanding the structure.

Open the file activity_main.xml. You'll see a canvas on which you can place buttons, text fields, and images. Each element is called a View. For example, to add a button, the tag <Button>is used. Each element has attributes: width, height, padding, text and identifier.

The identifier (android:id) is a critical parameter. It allows you to associate a visual element with code in an Activity class. Without an id, you will not be able to programmatically change the text on a button or attach a click handler to it. Always give elements meaningful names, such as btn_submit or text_welcome.

⚠️ Attention: Interfaces and names of components in Android Studio may change with updates. If you don't find a button in the menu, check the official documentation or use the settings search (Ctrl+Shift+A).

Try to create a simple interface: a header TextView in the center and a button Button below it. Use the attribute android:layout_constraint to position elements relative to the edges of the screen or each other. This will ensure correct display on smartphones with different diagonals.

Writing the application logic

After the interface is ready, you need to revive it. Go to file MainActivity.kt. Here you will write code that responds to user actions. In the Kotlin language, variables are declared with the keywords val (immutable) or var (changeable). Strict typing helps to avoid many mistakes even at the coding stage.

To associate a button with an action, you need to find it by ID in the method onCreate. Then an event listener (setOnClickListener) is assigned. Inside this listener you write a command that will be executed when clicked. This could be displaying a message, switching to another screen, or a mathematical calculation.

button.setOnClickListener {
textView.text = "Hello, world!"
}

This small piece of code changes the text in the field when clicked. Application logic is built from many such simple interactions. Variables, loops and conditional statements are used to work with data. It is important to remember about the Activity life cycle: methods onStart, onPause, onStop are called by the system at certain moments, and useful logic can also be written there, for example, saving data.

• 🔍 Use findViewById or synthetic properties to access UI elements.
• 🧠 Learn basic constructs: if/else, when, for, while.
• 📦 Use SharedPreferences or Room database to store data.
• 🌐 To work with the network, connect the Retrofit library or use the standard HttpClient.

Build, test and publish

Once the code is written and tested on the emulator, it's time to create the installation file. From the Android Studio menu, select Build → Build Bundle(s) / APK(s) → Build APK(s). The system will compile the project and create a file with the extension .apk. This file can be transferred to the phone and installed manually by enabling developer mode.

However, for distribution among users, it is better to use the Google Play store. To do this, you need to create a developer account (one-time fee of $25) and prepare a release version of the application. Unlike the debug version, the release version must be signed with a special digital key that confirms authorship.

The publishing process includes filling out the application card: description, screenshots, icon, category and privacy policy. Google moderation can take anywhere from a few days to a week. Be prepared for the fact that the application may be rejected due to violation of rules or technical errors.

Remember that the first application is rarely perfect. Errors, crashes, and design flaws are a normal part of the learning process. The main thing is to launch the project, get feedback and start working on the second version.

Frequent questions for beginners (FAQ)