Android Studio Activity LifeCycle
Syntax
The Activity Lifecycle comprises of the following methods:
void onCreate(Bundle savedInstanceState)
void onStart()
void onResume()
void onPause()
void onStop()
void onDestroy()
Example
public class MainActivity extends AppCompatActivity {
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
Log.d("Lifecycle", "onCreate invoked");
}
@Override
protected void onStart() {
super.onStart();
Log.d("Lifecycle", "onStart invoked");
}
@Override
protected void onResume() {
super.onResume();
Log.d("Lifecycle", "onResume invoked");
}
@Override
protected void onPause() {
super.onPause();
Log.d("Lifecycle", "onPause invoked");
}
@Override
protected void onStop() {
super.onStop();
Log.d("Lifecycle", "onStop invoked");
}
@Override
protected void onDestroy() {
super.onDestroy();
Log.d("Lifecycle", "onDestroy invoked");
}
}
Output
When you open the activity in your app, the following console log output will be shown:
onCreate invoked
onStart invoked
onResume invoked
When you press the back button, the following console log output will be shown:
onPause invoked
onStop invoked
onDestroy invoked
Explanation
The Android Activity Lifecycle is a set of states that an activity goes through from its creation to its destruction. An activity can be in one of four states: running, paused, stopped, or destroyed.
The lifecycle methods are invoked automatically by the Android operating system as an activity transitions between these states. The onCreate() method is always the first method called when an activity is launched.
The onStart() and onResume() methods are invoked when the activity becomes visible to the user.
The onPause() method is called when the activity is partially visible and loses focus.
The onStop() method is called when the activity is no longer visible to the user.
Finally, the onDestroy() method is called when the activity is destroyed and removed from memory.
Use
Understanding the Activity Lifecycle is essential for developing Android applications. It ensures that the app runs smoothly and efficiently, and also helps to prevent memory leaks and other errors.
Developers can also use the Android Lifecycle components to manage the lifecycle of their activities more effectively. These components include LifecycleObserver, LifecycleOwner, and LifecycleRegistry.
Important Points
- Always call the superclass method when overriding any lifecycle method.
- Don't rely on the onDestroy() method to release resources, as it may not always be called.
- Be aware that the activity can be destroyed at any time, so always save important data before the activity is destroyed.
- It is important to maintain a proper app control flow while handling different activity states.
Summary
In this article, we covered the syntax, example, and explanation of the Android Activity Lifecycle. We also discussed how to use the Lifecycle components and listed some important points to keep in mind while designing your app's architecture. A clear understanding of the Activity Lifecycle is essential for developing robust and efficient Android applications.