Android Lifecycle

The Android lifecycle is a series of states through which an Android application progresses during its execution. Understanding these states is essential for managing resources efficiently and ensuring a smooth user experience.

Lifecycle Overview

An Android app has multiple components, with Activity and Fragment being the most common. Each of these components has a defined lifecycle managed by the Android operating system.

Activity Lifecycle

The activity lifecycle consists of the following methods:

1. onCreate()

   • Called when the activity is first created.
   • Used for initialization, such as setting the layout and initializing variables.

2. onStart()

   • Called when the activity becomes visible to the user.

3. onResume()

   • Called when the activity starts interacting with the user.
   • The app is now in the foreground and the user can interact with it.

4. onPause()

   • Called when the system is about to resume another activity.
   • Use this method to pause operations such as animations or sensor updates.

5. onStop()

   • Called when the activity is no longer visible to the user.

6. onRestart()

   • Called when the activity is being restarted after being stopped.

7. onDestroy()

   • Called before the activity is destroyed.
   • Use this method to release resources and clean up tasks.

Activity lifecycle

• App Launch → onCreate, onStart, onResume
• App Minimize → onPause, onStop | App Restore → onRestart, onStrat, onResume
• Open Another Activity → onPause, onStop | Back → onRestart, onStart, onResume
• App Orientation Change → onPause, onStop, onDestroy, onCraete, onStart, onResume

Lifecycle Diagram

Fragment Lifecycle

Fragments have a similar but slightly extended lifecycle compared to activities:

1. onAttach()

   • Called when the fragment is associated with its activity.

2. onCreate()

   • Called to initialize the fragment.

3. onCreateView()

   • Called to create and return the fragment's UI.

4. onViewCreated()

   • Called after the fragment's view is created.

5. onStart()

   • Called when the fragment becomes visible.

6. onResume()

   • Called when the fragment starts interacting with the user.

7. onPause()

   • Called when the fragment is no longer interacting with the user.

8. onStop()

   • Called when the fragment is no longer visible.

9. onDestroyView()

   • Called when the fragment's view is destroyed.

10. onDestroy()

    • Called when the fragment is being destroyed.

11. onDetach()

    • Called when the fragment is detached from its activity.

Lifecycle Diagram

Best Practices

• Always release resources such as database connections, threads, or listeners in onStop() or onDestroy().
• Save the state of the activity in onSaveInstanceState() to restore it later.
• Use ViewModel or LiveData to manage data efficiently and persist it across configuration changes.
• Avoid lengthy operations on the main thread. Use background threads or AsyncTask for such tasks.

Additional Resources

• Android Developer Documentation: Activity Lifecycle
• Android Developer Documentation: Fragment Lifecycle

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Happy coding! 🎉