android-sdk

android-sdk Best Practices (Java)

This guide outlines the essential practices for building robust, performant, and maintainable Android applications using Java, adhering to modern standards and leveraging the AndroidX ecosystem.

1. Code Organization and Structure

1.1 Modular Architecture (MVVM) Adopt a clean, modular architecture, with MVVM (Model-View-ViewModel) as the standard. This promotes separation of concerns, testability, and scalability.

❌ BAD: Tight Coupling

// Activity directly fetching data and updating UI
public class UserProfileActivity extends AppCompatActivity {
    private TextView userName;
    // ... other UI elements

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_user_profile);
        userName = findViewById(R.id.user_name);
        // Direct network call on UI thread (or poorly managed background thread)
        new Thread(() -> {
            String name = fetchUserNameFromNetwork(); // Blocking call
            runOnUiThread(() -> userName.setText(name));
        }).start();
    }
    // ...
}

✅ GOOD: MVVM with Repository Pattern

// ui/UserProfileActivity.java
public class UserProfileActivity extends AppCompatActivity {
    private UserProfileViewModel viewModel;
    private TextView userName;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_user_profile);
        userName = findViewById(R.id.user_name);

        viewModel = new ViewModelProvider(this).get(UserProfileViewModel.class);
        viewModel.getUserName().observe(this, name -> {
            userName.setText(name);
        });
    }
}

// ui/UserProfileViewModel.java
public class UserProfileViewModel extends AndroidViewModel {
    private UserRepository userRepository;
    private MutableLiveData<String> userName = new MutableLiveData<>();

    public UserProfileViewModel(@NonNull Application application) {
        super(application);
        this.userRepository = new UserRepository(application); // Injected via Hilt in real app
        loadUserName();
    }

    public LiveData<String> getUserName() {
        return userName;
    }

    private void loadUserName() {
        // Use ExecutorService or RxJava for background work
        Executors.newSingleThreadExecutor().execute(() -> {
            String name = userRepository.fetchUserName();
            userName.postValue(name); // Post value to main thread
        });
    }
}

// data/UserRepository.java
public class UserRepository {
    // In a real app, this would interact with Room, Retrofit, etc.
    public String fetchUserName() {
        // Simulate network call
        try { Thread.sleep(2000); } catch (InterruptedException e) {}
        return "John Doe";
    }
}