In the below example I have created Activity life cycle. Activity start's with a call on onCreate() callback method. There is a sequence of callback methods that start's an activity and a sequence of callback methods. See the below example for detail.

. onCreate() - called before the first components of the application starts

. onStart()- Called when the activity is becoming visible to the user.

. onPause() - Called when the system is about to start resuming a previous activity. This is
typically used to commit unsaved changes to persistent data, stop animations and other things
that may be consuming CPU, etc. 

. onStop()- Called when the activity is no longer visible to the user, because another
activity has been resumed and is covering this one. This may happen either
because a new activity is being started, an existing one is being brought in front of
this one, or this one is being destroyed.

. onDestory()-The final call you receive before your activity is destroyed. This can happen either because the activity is finishing (someone calledfinish() on it.
Program-

public class FindnerdActivity extends Activity {

  @Override
  protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    notify("onCreate");
  }

  @Override
  protected void onPause() {
    super.onPause();
    notify("onPause");
  }

  @Override
  protected void onResume() {
    super.onResume();
    notify("onResume");
  }

  @Override
  protected void onStop() {
    super.onStop();
    notify("onStop");
  }

  @Override
  protected void onDestroy() {
    super.onDestroy();
    notify("onDestroy");
  }

  @Override
  protected void onRestoreInstanceState(Bundle savedInstanceState) {
    super.onRestoreInstanceState(savedInstanceState);
    notify("onRestoreInstanceState");
  }

  @Override
  protected void onSaveInstanceState(Bundle outState) {
    super.onSaveInstanceState(outState);
    notify("onSaveInstanceState");
  }

  private void notify(String methodName) {
    String name = this.getClass().getName();
    String[] strings = name.split("\\.");
    Notification noti = new Notification.Builder(this)
     .setContentTitle(methodName + " " + strings[strings.length - 1]).setAutoCancel(true)
     .setSmallIcon(R.drawable.ic_launcher)
     .setContentText(name).build();
    NotificationManager notificationManager = 
        (NotificationManager) getSystemService(NOTIFICATION_SERVICE);
    notificationManager.notify((int) System.currentTimeMillis(), noti);
  }

}