Fragment lifecycle events in LifeCycleAware Fragment

Question

I have a lifecycle aware fragment and a LifecycleObserver class

        public class MyFragment extends Fragment {
            @Override
            public void onCreate(@Nullable Bundle savedInstanceState) {
                super.onCreate(savedInstanceState);
                new MyObserver(this);

            }

            @Nullable
            @Override
            public View onCreateView(LayoutInflater inflater, @Nullable ViewGroup container, Bundle savedInstanceState) {
                return inflater.inflate(R.layout.activity_main, container, false);
            }
        }

Following is my Observer class where it logs all the fragment events propery

        public class MyObserver implements LifecycleObserver {
            private static final String TAG = "MyObserver";
            public MyObserver(LifecycleOwner lifecycleOwner) {
                lifecycleOwner.getLifecycle().addObserver(this);
            }

            @OnLifecycleEvent(Lifecycle.Event.ON_CREATE)
            public void onCreate(){
                Log.d(TAG, "onCreate: ");
            }

            @OnLifecycleEvent(Lifecycle.Event.ON_PAUSE)
            public void onPause(){
                Log.d(TAG, "onPause: ");
            }

            @OnLifecycleEvent(Lifecycle.Event.ON_DESTROY)
            public void onDestroy(){
                Log.d(TAG, "onDestroy: ");
            }

            @OnLifecycleEvent(Lifecycle.Event.ON_START)
            public void onStart(){
                Log.d(TAG, "onStart: ");
            }

        }

I want to listen to fragment specific lifecycle events like onDestroyView and onActivityCreated but these events are not there in

Lifecycle.Event. It contains only activity events. How can I listen for fragment events in my observer

Poundfoolish

Were you able to find anything about this? – Yeah

I am also trying to figure this out. Did you find a solution? – Wieren

Any way to achieve this using a lifecycle observer? The answers below can be implemented without lifecycle observer by writing our own custom methods and calling from fragments. – Cholera

Answer 1

You can observe the fragment's viewLifecycleOwner lifecycle.

viewLifecycleOwner.lifecycle.addObserver(yourObserverHere)

Then the fragment's onDestroyView lifecyle method is tied to the @OnLifecycleEvent(Lifecycle.Event.ON_DESTROY) annotated method.

Note that the fragment's viewLifecycleOwner is only available between onCreateView and onDestroyView lifecycle methods.

Rovner

@OnLifecycleEvent(Lifecycle.Event.ON_DESTROY) called when the fragment is destroyed not in destroyview – Multiplier

@Multiplier it depends on which lifecycle, the fragment lifecycle or the fragment's view lifecycle. – Rovner

Needs clarification – Multiplier

@Multiplier Please read about getViewLifecycleOwner() method and you will understand it. – Rovner

@Multiplier check my answer for more details regarding ON_DESTROY – Incandescence

Answer 2

Just a supplement to Basim Alamuddin's answer：

As you can see in the resource codes, @OnLifecycleEvent(Lifecycle.Event.ON_DESTROY) is also called when you add an observer to viewLifecycleOwner: viewLifecycleOwner.lifecycle.addObserver(this)

// androidx.fragment.app.Fragment

void performDestroyView() {
    if (mView != null) {
        mViewLifecycleOwner.handleLifecycleEvent(Lifecycle.Event.ON_DESTROY);
    }
    onDestroyView();

void performDestroy() {
    mLifecycleRegistry.handleLifecycleEvent(Lifecycle.Event.ON_DESTROY);
    onDestroy();

Incandescence

Answer 3

Well, according to this, literally onDestroyView will be called after onStop. So, If you need the logic to run before onDestroyView or detecting it, i think it's is best to call it or detect in the fragment's onStop() method. In your case, i think you need to implement Lifecycle.Event.ON_STOP & Lifecycle.Event.ON_START for onActivityCreated.

Hope it helps you.

Bucaramanga

developer.android.com/guide/fragments/lifecycle – Quaky

Answer 4

Fragment Life Cycle

onCreateView()

Called to create the view hierarchy associated with the fragment.

onDestroyView()

Called when the view hierarchy associated with the fragment is being removed.

Plexor

My question is about Architecture Components – Poundfoolish