Reacting to activity lifecycle in ViewModel

Question

I\'m trying to create an app which will use MVVM architecture and there\'s one thing I quite don\'t understand.

Official Android docs say that\'s not a good idea to refe

Answer 1

If you need to have a ViewModel be lifecycle aware, then you can have it implement LifeCycleObserver and override life cycle events as necessary. Example,

public class MyModel extends ViewModel implements
    LifecycleObserver {

  @OnLifecycleEvent(Lifecycle.Event.ON_STOP)
  protected void onLifeCycleStop() {
      // do something
  }
}

In the activity or fragment then you can add the view model to the activity life cycle owner.

public class MyActivity extends AppCompatActivity {

  protected MyModel mMyModel;

  @Override
  public void onCreate(Bundle savedInstanceState) {
      super.onCreate(savedInstanceState);

      mMyModel = ViewModelProviders
          .of(this)
          .get(MyModel.class);

      getLifecycle().addObserver(mMyModel);
  }
}