Creating mobile apps for the Google platform is exciting a process that opens access to a huge audience of users around the world. The modern ecosystem offers developers powerful tools and programming languages that allow them to implement ideas of any complexity. Native development today is considered the gold standard, providing maximum performance and access to all device functions.
Language selection Kotlin is not used as the main tool is accidental, because it has been officially recommended by Google since 2019. This language is concise, secure, and fully compatible with existing Java libraries. If you are wondering how to write an Android application in kotlin, then this material will become your guide to the world of mobile development.
Before you start writing code, you need to prepare a working environment and understand the basic concepts. To compile projects, the Gradle build system is used, which manages dependencies and build configuration. Understanding these fundamental things will save you hours of debugging in the future and allow you to focus on the logic of the product.
Preparing the development environment and installing Android Studio
The first and most important step is to install a specialized integrated development environment (IDE). The official tool is considered Android Studio, which is based on the platform IntelliJ IDEA. You can download the current version on the official developer portal, where the latest stable builds for Windows, macOS and Linux are always available.
During the installation process, the system will prompt you to select components, which must include Android SDK (Software Development Kit). This set contains the necessary libraries, emulators and debugging tools. Without a correctly installed SDK, code compilation will be impossible, since the compiler will not find the base classes of the system.
After installation is complete, initial setup of the environment will be required. The menu File → Project Structure checks the JDK version and the path to the SDK. It's also worth making sure you have the latest plugin updates installed, as support for new versions of Android is constantly improving.
It is important to consider that hardware requirements may be high. For comfortable work, it is recommended to have at least 16 GB of RAM and an SSD drive. Running the emulator and compiling the project simultaneously consumes significant CPU resources.
⚠️ Warning: Antivirus apps can sometimes block Gradle or the emulator from working. If strange build errors occur, add the project folder and SDK to the antivirus exceptions.
Creating the first project and file structure
Having launched the development environment, select the option to create a new project through the menu File → New → New Project. In the window that opens, you need to select a template, for example Empty Activity, which will create the minimum required structure to start. This will allow you to avoid unnecessary code and understand the basics yourself.
The key configuration file is build.gradle (Project level) and build.gradle (Module level). The module file contains dependencies and SDK versions. This is where you specify the minimum version of Android on which your application will run through the parameter minSdk.
The folder structure in the project is standardized and includes several important directories. In folder manifests there is a file AndroidManifest.xmlthat describes the application components and the requested permissions. The directory java contains the source code, and res stores resources: images, strings and interface layouts.
☑️ Structure of the new project
The main entry point into the application is the activity class, usually called MainActivity. It contains a method onCreatethat is called by the system when the app starts. This is where the visual interface is tied to the operating logic.
Basics of the Kotlin language for Android
The Kotlin language is famous for its expressiveness and elimination of many problems inherent in Java. One of the key features is working with nullable types, which protects the code from errors NullPointerException. A variable can contain null only if its type is declared with a question mark, for example, String?.
Lambda expressions and functionals are often used to work with the interface. They allow blocks of code to be passed as arguments to functions, making the code more readable. For example, handling a button click is often written as a short-circuit function.
- 📱 Val and Var: use val for immutable variables and var for mutable variables to control the state of the data.
- 🚀 Coroutines: asynchronous programming made easy with built-in support for background coroutines tasks.
- 🧩 Data Classes: special classes for storing data that automatically generate equals, hashCode and toString methods.
Particular attention should be paid to expanding the functionality of existing classes. The extension function mechanism allows you to add new methods to classes from the Android SDK without inheriting them. This is a powerful tool for creating utilities and helper classes.
Why is Kotlin better than Java for beginners?
Kotlin requires less template code (boilerplate), has a more strict type system and built-in support for modern programming paradigms, which reduces the entry barrier.
Interface layout using XML and Jetpack Compose
The traditional way of describing the interface in Android is the XML markup language. Layout files are located in the directory res/layout and represent a hierarchy of View objects. Each element can be assigned a unique ID so that it can then be managed from Kotlin code.
However, modern development is increasingly turning to the declarative approach through the library Jetpack Compose. This tool allows you to create UI directly in Kotlin, eliminating the need for XML. Compose is highly performant and flexible, allowing you to create complex animations and responsive layouts with less code.
When choosing an approach, it is worth considering the requirements of the project. If you need to support very old versions of Android or work with legacy code, XML remains relevant. For new projects, especially startups, it is recommended to immediately study and implement Compose.
| Characteristics | XML Layouts | Jetpack Compose |
|---|---|---|
| Syntax | Individual XML files | Kotlin code |
| Training | Requires knowledge of two languages | Kotlin only |
| Preview | Basic preview | Interactive and fast |
| Status | Manual control | Automatic (State) |
Regardless of the chosen method, it is important to adhere to the principles of adaptability. The interface must display correctly on screens of various sizes and orientations. To do this, use ConstraintLayout in XML or size modifiers in Compose.
Implementing logic and working with components
After creating the interface, you need to associate it with app logic. The classic approach uses a method findViewById to find elements by ID, although in Compose this is done through function parameters. The resulting objects allow you to read user input data and display the results of calculations.
The component Intentis used to navigate between screens. It conveys information about what activity to run and may contain additional data (Extras). Proper activity lifecycle management is critical to maintaining state when rotating the screen or switching applications.
Use ViewBinding or DataBinding instead of findViewById for safer and faster work with XML interfaces in older projects.
Working with background tasks requires the use of coroutines. Running long-running operations, such as downloading data from the network or working with a database, in the main thread will cause the interface to hang and an ANR (Application Not Responding) error.
⚠️ Warning: Never execute network requests in the Main Thread. This will cause the application to crash on devices with Android 11 and higher due to the StrictMode policy.