The modern mobile market continues to grow, and the demand for qualified specialists capable of creating high-quality applications remains high. Despite the emergence of new versions of the operating system, understanding the architecture Android 9 Pie (API 28) is fundamental for any novice programmer. This version has made significant changes to battery management and working with notifications, which makes it an excellent base for learning the principles of development.
Many beginners mistakenly believe that to get started they need to immediately master the latest tools, ignoring stable and time-tested solutions. However, it is on the basis Android 9 that one can clearly see the evolution of approaches to security and code optimization. In this guide, we'll walk you through every step from setting up your development environment to publishing your finished product.
Your journey to creating your own apps starts with choosing the right tools and understanding how the Google ecosystem works. Don't be afraid of complexity: with consistent study of the material, even a person without a technical background will be able to write their first code. The main thing is patience and practice.
Choosing a programming language and preparing the environment
The first step towards creating applications is choosing a programming language. For a long time, it was the de facto standard, in which a significant part of the legacy code in large companies is written. However, since 2017, Google has officially announced Java, in which a significant part of the legacy code in large companies is written. However, since 2017, Google has officially announced Kotlin preferred language for Android development. To work with Android 9, it is recommended to use Kotlin, as it has a more concise syntax and built-in protection against errors associated with null values.
In addition to choosing a language, it is critical to install the correct development environment. The industry standard is Android Studiobased on the IntelliJ IDEA platform. It provides all the necessary tools: from a visual interface editor to a powerful memory profiler. The distribution should be downloaded exclusively from the official website of the developers to avoid malicious embeds.
The installation process may take some time, since the IDE requires downloading additional components, including Android SDK (Software Development Kit). It is the SDK that contains the libraries, emulators and debugging tools necessary to compile and run your code on a device or virtual machine.
⚠️ Attention: When installing Android Studio, make sure that you have at least 8 GB of free space on your disk. Caching libraries and emulator images takes up a significant amount of memory, and a lack of memory can lead to compilation errors.
After installation, you need to set up environment variables so that debugging commands work from the terminal. For Windows users this is done through system settings, and for macOS and Linux users this is done by editing the shell configuration file. Correctly setting the folder path platform-tools will save you hours of troubleshooting in the future.
☑️ Preparing the workspace
Setting up the project and working with Android Studio
Creating a new project in the development environment is not just a matter of clicking the “New Project” button, but a process of defining the architecture of the future application. When you launch the New Project Wizard, you will be prompted to select the minimum SDK version. For training purposes and compatibility with a wide range of devices, the optimal choice would be API 28corresponding to Android 9.
The Android Studio interface may seem overloaded for a beginner, but the main panels have a clear purpose. The code editor window occupies a central place, on the left there is a project panel with a file structure, and at the bottom there is a window Logcat for tracking system logs. Understanding where to look for runtime errors is a key developer skill.
It is important to immediately pay attention to the version control system. C Git integration is built into the IDE, which allows you to save a history of code changes and roll back to working versions in case of unsuccessful edits. Ignoring this tool in the early stages often results in lost days of work when important files are accidentally deleted.
Use keyboard shortcuts for navigation. For example, double Shift opens a search throughout the entire project, which significantly speeds up working with large code bases.
The Android project structure has a strict hierarchy. The source code is in the folder java, resources (images, strings, layouts) are in the folder res, and the application manifest, which describes its components and access rights, lies in the root of the module app. Violation of this structure can lead to the fact that the compiler simply does not see your resources.
Architecture fundamentals and application components
An Android application consists of four main types of components, each of which plays its own role in the app life cycle. Understanding the difference between them is essential to creating a stable and responsive interface. The main component is Activity, which is a single screen with a user interface.
In addition to activities, there are services (Services), which perform lengthy operations in the background without user interaction. Also important are broadcast receivers (Broadcast Receivers), which respond to system events, and content providers (Content Providers), which manage access to data between applications.
The life cycle of an activity is the sequence of states through which the screen passes: from creation (onCreate) to destruction (onDestroy). Android 9 has tightened the requirements for background activity, so the developer must intelligently handle onPause and onStopmethods to preserve application state when minimized.
⚠️ Warning: Never perform long operations, such as network queries or database reads, on the main thread (UI Thread). This will lead to an error
Application Not Responding (ANR)and application crash.
For interaction between components, a special object is used - Intent. It acts as a message that passes data from one activity to another or starts a service. Correct use of explicit and implicit intents allows you to create a modular application architecture.
What is a Manifest file?
AndroidManifest.xml is the passport of your application. It declares all activities, services, access rights to hardware (camera, Internet) and the minimum version of Android on which the app can run. Without correctly configuring this file, the application will not install.
Creating an interface and working with layouts
The user interface in Android is described using XML files located in the directory res/layout. Although the visual editor allows you to drag and drop elements with the mouse, professional developers prefer to write markup code manually or use modern tools like Jetpack Compose (although for Android 9, classic XML is still relevant).
Various layouts serve as the basis for building the interface (Layouts). The most popular are ConstraintLayout, which allows you to create complex interfaces without nesting, and LinearLayout for sequential arrangement of elements. Choosing the right container affects screen rendering performance.
All text lines and sizes must be placed in separate resource files (strings.xml and dimens.xml). This rule localization allows you to easily adapt the application to different languages and screens of different devices without rewriting the layout code.
| UI element | Purpose | Usage example |
|---|---|---|
| TextView | Text display | Headings, product descriptions |
| Button | Interactive button | Submit form, go to screen |
| ImageView | Graphics display | Avatars, logos, photos |
| RecyclerView | List of elements | News feed, contacts |
When working with graphics, it is important to consider the pixel density of the screen. All sizes in layouts must be specified in units dp (density-independent pixels), and fonts - in sp (scale-independent pixels). This ensures that your application will look equally good on a small smartphone and on a large tablet.
Data storage and working with network
Most modern applications require saving user data or downloading information from the Internet. For local storage of simple settings, a mechanism SharedPreferencesis used, which is a storage of key-value pairs. For more complex data structures, a database is used SQLite or an abstraction above it - Room.
Networking in Android 9 has undergone important changes in terms of security. By default, the system blocks unencrypted HTTP traffic, requiring the use of the protocol HTTPS. If your application needs to communicate with a legacy server, you will have to explicitly allow cleartext traffic in the manifest settings, which is not recommended for production.
To perform network requests, the library Retrofit in conjunction with OkHttphas become an industry standard. They allow you to asynchronously receive data in JSON format and automatically convert it into Java or Kotlin objects. Synchronous requests on the main thread are still prohibited and will crash the application.
⚠️ Attention: Starting with Android 9, access to non-public fields via reflection is limited. If you use libraries that rely on the system's hidden API, your application may become unstable or fail to launch at all.
When working with databases, it is important to remember schema migration. When updating an application version, the table structure may change, and if a migration script is not provided, the user will lose all of his data during the update. The Room library helps automate this process through annotations.
Debugging, testing and publishing
Writing code is only half the battle. The second, no less important part is finding and correcting errors. The tool Logcat allows you to see in real time all messages from the system and your application. The ability to filter logs by tags and severity levels (Error, Warning, Debug) is critical for quickly diagnosing problems.
Before releasing the application, it is necessary to conduct testing on various devices. The Android Studio emulator allows you to simulate different screen configurations and OS versions, but nothing can replace testing on a real one. Connect the device via USB, enable developer mode and start debugging directly. Android smartphone. Connect the device via USB, enable developer mode and start debugging directly.
When the application is ready, the stage of publication in the Google Play Console begins. You will need to create a developer account, prepare graphic materials (icons, screenshots) and fill out a description. The moderation process can take from several hours to several days, depending on the complexity of the application and compliance with the rules of the store.
Regular testing on real devices reveals 80% of errors that emulators miss, especially those related to the operation of the camera and sensors.
Do not forget about optimizing the size of the APK file. Using image compression formats, removing unused resources, and splitting code by processor architecture (ABI splits) will help make your application easier and faster for users to download.
Do you need to know mathematics to develop for Android?
For most standard applications (news, social networks, utilities), deep knowledge of higher mathematics is not required. Logic and understanding of algorithms is enough. However, if you plan to develop games, graphics applications, or complex financial calculators, knowledge of linear algebra and geometry will be a big advantage.
How long does it take to learn Android from scratch?
With intensive training (4-6 hours a day), a basic level that allows you to create simple applications is achieved in 3-4 months. For a Junior level developer ready to work in a team, it usually takes 6 to 12 months of practice and studying architectural patterns.
Is it possible to develop on Android 9 on a weak computer?
Yes, it is possible, but with limitations. The emulator is very demanding on RAM (16 GB recommended). On a computer with 8 GB of RAM, it is recommended to use a physical device for debugging and disable unnecessary plugins in Android Studio to save resources.
What is the difference between APK and AAB?
APK is an installation package that can be transferred as a file. AAB (Android App Bundle) is a new publishing format on Google Play that allows the store to generate optimized APKs for a user's specific device, reducing the download file size.
Is it worth learning Java or Kotlin right away?
It is recommended to start with Kotlin right away. It is fully compatible with Java, but requires less code, is more secure, and is supported by Google as a preferred language. Knowledge of Java will be useful later for reading old projects, but starting with Kotlin will be more effective.