Android App Lifecycle

Introduction

The Android app lifecycle is a series of states that an application goes through from when it is created to when it is destroyed. Understanding these states is crucial for managing resources and creating a smooth user experience.

Lifecycle Methods

Android apps are primarily managed through the Activity and Fragment classes. The main lifecycle methods are:

• onCreate(): Called when the activity is first created.
• onStart(): Called when the activity becomes visible to the user.
• onResume(): Called when the activity starts interacting with the user.
• onPause(): Called when the activity is partially obscured or when another activity comes to the foreground.
• onStop(): Called when the activity is no longer visible to the user.
• onDestroy(): Called before the activity is destroyed.
• onRestart(): Called when the activity is being restarted after being stopped.

public class MainActivity extends AppCompatActivity {
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
    }

    @Override
    protected void onStart() {
        super.onStart();
        // Code to run when the activity is visible
    }

    @Override
    protected void onResume() {
        super.onResume();
        // Code to run when the activity starts interacting with the user
    }

    @Override
    protected void onPause() {
        super.onPause();
        // Code to run when another activity is in the foreground
    }

    @Override
    protected void onStop() {
        super.onStop();
        // Code to run when the activity is no longer visible
    }

    @Override
    protected void onDestroy() {
        super.onDestroy();
        // Code to run before the activity is destroyed
    }
}
                

Best Practices

To manage the app lifecycle effectively, consider the following best practices:

• Release resources in onPause() or onStop() to save memory.
• Use the onSaveInstanceState() method to save UI state when the activity is paused or stopped.
• Keep the onCreate() method lightweight by initializing resources only when needed.
• Handle configuration changes (like screen rotation) to avoid activity recreation.

FAQ