Creating a mobile application is not just writing code, but a complex process of interaction between many tools, each of which solves its own problems. When beginners ask what exactly apps for Android are written in, they often expect to hear one name, but the reality is much richer. Android ecosystem based on several key components: a programming language, an integrated development environment (IDE) and a set of libraries that together turn lines of code into a working .apk or .aab file.
The foundation of the entire system for a long time remained the Dalvik virtual machine, and then its successor ART (Android Runtime), which allow you to run bytecode on a wide variety of devices, from budget smartphones to powerful tablets. This is why developers can choose different languages, knowing that the operating system will be able to “understand” them and run them. It is important to understand that the choice of tool is often dictated not only by the personal preferences of the programmer, but also by business requirements, the need for cross-platform or the specifics of the graphical interface.
In this article we will look in detail at which languages are native, which frameworks allow you to write code for iOS and Android at once, and also consider the environments in which the magic of creating applications happens. You will find out why Google has shifted its focus to Kotlin, and whether it is worth learning today Java to start your career.
Native programming languages: the basis of the ecosystem
Native development involves creating applications that run directly on the device’s operating system, using its native APIs and capabilities. This ensures maximum performance and access to all hardware features such as cameraGPS, accelerometer and Bluetooth. For the Android platform, there have historically been two main directions that have dominated the industry for more than ten years.
The first and for a long time the only official language was Java. It is a powerful, strongly typed language in which much of the Android operating system itself and millions of apps on Google Play are written. Despite the emergence of new competitors, Java remains the de facto standard for many corporate projects and banking systems, where stability and the presence of a huge number of proven libraries are important. The Java code is compiled into bytecode, which is then executed by the ART virtual machine.
The second, and now priority, language is Kotlin. JetBrains created it as a more modern and concise alternative to Java, eliminating many of the shortcomings of its predecessor's verbosity. In 2019, Google announced a transition to strategy Kotlin-first, which means: new APIs and tools are primarily optimized for this language. Kotlin is fully compatible with Java, which allows it to be gradually introduced into older projects, and has built-in protection against null-pointer exceptions, which makes applications more stable.
⚠️ Attention: Despite the popularity of Kotlin, knowledge of Java is still required when supporting legacy code (old projects). Many large companies have millions of lines of code in Java, and no one will completely rewrite them in the coming years.
The choice between these two languages for native development is now shifting towards Kotlin, especially for new projects. However, basic understanding the principles of the Java machine and object-oriented programming remain a critical skill for any Android developer, regardless of the chosen syntax.
Cross-platform frameworks and hybrid development
If native development requires writing separate code for Android and iOS, then cross-platform solutions allow you to create a single code base that works on both platforms. This significantly saves time and budget, allowing teams of 2-3 people to release full-fledged products. However, this comes at the cost of performance or the size of the final application file.
One of the most popular tools today is Flutter from Google. It uses the Dart programming language and its own rendering engine, which allows for high frame rates (60/120 FPS) and smooth animation. Flutter applications are compiled into native code, which makes them very fast. Another giant is React Native from Facebook, which is based on JavaScript and allows you to use ready-made web components, adapting them for mobile platforms.
There are other solutions, such as Xamarin (now part of .NET MAUI), which uses C#, or Ionic, which It is essentially a website packaged in an application shell. The choice of a specific framework depends on the tasks:
- 🚀 Flutter —ideal for beautiful, custom interfaces and startups where you need to quickly enter two markets.
- 🌐 React Native —the best choice for teams with experience in web development and projects based on the JavaScript ecosystem.
- 🏢 .NET MAUI (Xamarin) —preferable for the corporate sector where the infrastructure is already used Microsoft.
- 🎮 Unity / Godot is the only right choice if you are creating a mobile game and not a utilitarian application.
Why can cross-platform applications be heavier?
Native applications use only those libraries that the system needs. Cross-platform ones often carry an entire “engine” or “bridge” for communication with the OS, which increases the size of the installation file, sometimes up to 20-50 MB even for a simple application.
Integrated development environments (IDE)
Writing code “in Notepad” is possible, but extremely ineffective. To be productive, you need powerful tools that suggest syntax, find errors, and help manage project resources. The development environment is a programmer’s workplace, and the speed and comfort of work depends on its choice.
The undisputed leader and official recommendation of Google is Android Studio. This environment is built on IntelliJ IDEA and is tailored specifically to the needs of mobile development. It includes a device emulator, memory profiler, network analyzer and visual interface editor. Installing Android Studio is the first step any aspiring developer should take.
For those who prefer cross-platform development or work with other languages, there are alternatives. Visual Studio Code is a lightweight and fast editor that, with the help of plugins, turns into a powerful tool for Flutter or React Native. JetBrains IntelliJ IDEA (Ultimate paid version) also supports Android, but Android Studio (based on the Community version) is usually free and contains all the necessary plugins out of the box.
Do not install multiple versions of Android Studio at the same time on one machine unless necessary. They may conflict over emulators and system variables. If you need to test on different versions of the IDE, use portable versions.
Build systems and dependency management
A modern application is not one file with code, but a complex structure consisting of hundreds of libraries, resources (images, fonts) and configuration files. To assemble a working file from this “constructor”, you need assembly systems. In the Android world, the Gradle system has become the de facto standard for managing dependencies, library versions, and the compilation process. It is he who downloads the necessary packages from repositories (for example, Maven Central) and implements them into the project. The configuration occurs in files Gradle.
Gradle manages dependencies, library versions, and the compilation process. It is he who downloads the necessary packages from repositories (for example, Maven Central) and implements them into the project. Configuration happens in files build.gradle (or build.gradle.kts for Kotlin DSL), where all the necessary modules are written. Understanding how Gradle works is necessary to solve compilation errors that often arise when updating library versions.
In addition to Gradle, in some specific cases (for example, when developing system software or a kernel) it can be used CMake or NDK Build to compile native code in C/C++. However, for 95% of applications for creating user interfaces and logic, Gradle is used.
| Tool | Main function | Configuration language | Difficulty of learning |
|---|---|---|---|
| Gradle | Project assembly, management dependencies | Groovy / Kotlin DSL | High |
| Maven | Dependency management (less often for assembly) | XML | Medium |
| CMake | Building native code (C/C++) | CMakeLists.txt | Very high |
| Bazel | Building large monolithic projects (Google) | Starlark | Extreme |
Testing and debugging applications
Writing code is only half the battle. The app must work stably on thousands of different smartphone models with different screens and OS versions. To do this, developers use emulators and real devices. Android Virtual Device (AVD) allows you to run a virtual phone directly on your computer, simulating a specific model, for example, Pixel 6 with Android 14.
However, an emulator cannot completely replace a real test. It doesn't take into account battery, actual GPS signal, or network behavior when switching from Wi-Fi to 4G. That's why professionals always test final builds on physical devices. For remote testing, there are cloud farms, such as Firebase Test Lab, where you can run an application through hundreds of use cases.
The debugging process allows you to step through your code, stop it at certain lines, and view variable values in real time. This is the main method for finding logical errors. The Android Studio toolkit provides powerful tools for analyzing memory (Memory Profiler) and processor (CPU Profiler), which helps to find “leaks” and optimize the application.
☑️ Checklist before app release
Publishing and distribution
When the application is written, tested and debugged, it needs to be delivered to the user. The main distribution channel is the store Google Play. To publish, the developer must register a Google Play Console account (one-time fee $25) and prepare all the necessary metadata: screenshots, descriptions, privacy policies.
An important step is the creation of a release build. Previously, the format .apkwas used, but now Google requires the format Android App Bundle (.aab). This format allows the store to automatically optimize the application for the user's specific device, removing unnecessary resources (for example, images for screens that the user does not have), which reduces the download size.
⚠️ Attention: Google Play rules are constantly changing. Before publishing, be sure to check the app Policies section in the Developer Console. Violation of the rules (for example, regarding data collection or advertising) can lead to account blocking forever without the possibility of recovery.
There are alternative stores, such as Amazon Appstore, Galaxy Store (for Samsung) or Huawei AppGallery. To reach a global audience, it often makes sense to publish not only on Google Play, but also in these stores, although this requires additional customization of builds.
The Android App Bundle (.aab) format has been a mandatory standard for new applications on Google Play since August 2021. Old APK files for new downloads are no longer accepted.
Frequently asked questions (FAQ)
Do you need to know mathematics to write apps for Android?
To create standard applications (stores, social networks, utilities), basic school mathematics and logic are enough thinking. Higher mathematics is only required when developing complex 3D graphics, physics engines for games, or machine learning algorithms.
Is it possible to write code for Android in Python?
There is no direct way, since Android does not have built-in support for Python. However, there are wrapper frameworks such as Kivy or BeeWarethat allow you to write code in Python and compile it into an APK. But such applications often work slower than native ones and have limited access to the system API.
How long does it take to learn how to create simple applications?
With intensive training (4-6 hours a day), basic skills in the Kotlin language and working with Android Studio can be mastered in 2-3 months. Creating the first full-fledged, working application will take another 1-2 months of practice.
Do you need a powerful computer for Android development?
It is advisable to have at least 16 GB of RAM, since the emulator and IDE consume a lot of resources. It is better to have a processor with 4 cores or higher. On weak machines (8 GB RAM), development is possible, but compilation will be slow, which reduces productivity.