Android activities and app lifecycle

1. Introduction to activities

   Activity class, manifest declaration, starting activities and the entry-point model.

2. Activity lifecycle

   onCreate, onStart, onResume, onPause, onStop, onDestroy and state transitions.

3. Tasks and back stack

   Launch modes, task affinity, intent flags and the back stack.

4. Saving UI state

   onSaveInstanceState, ViewModel and persistent storage for UI state.

5. Process and app lifecycle

   Process priority, importance hierarchy and how the system kills processes.

6. Handling configuration changes

   Activity recreation on rotation and locale changes, configChanges attribute.

7. Fundamentals of app components

   Activities, services, broadcast receivers and content providers as app entry points.

Each section links to the official page. Titles and summaries by Extra Credit; the docs belong to their authors.