How to get LifecycleOwner in a Fragment?

Question

I need to get the LifecycleOwner to pass it in my FirestoreRecyclerViewOption but Fragment doesn't implement Lifecycle.

So, how to get that?

My Fragment implements LifecycleOnwer as shown in the following code example,

public class ListRestFragment extends Fragment implements LifecycleOwner 

after in the onCreateMethod,

  lifecycleRegistry = new LifecycleRegistry(this);
        lifecycleRegistry.setCurrentState(Lifecycle.State.CREATED);

and to finish

@Override
    public void onStart() {
        super.onStart();
        lifecycleRegistry.setCurrentState(Lifecycle.State.STARTED);
    }

    @NonNull
    @Override
    public Lifecycle getLifecycle() {
        return lifecycleRegistry;
    }

I follow this example but it doesn't work

Attempt to invoke virtual method 'androidx.lifecycle.Lifecycle$State androidx.lifecycle.Lifecycle.getCurrentState()' on a null object reference

I need it to edit My FirestoreRecyclerViewOption and setLifeCycleOwner because it is always null and I have an NullPointer everytime.

Mme

Are you using the deprecated framework Fragments? All Support Library / AndroidX fragments implement LifecycleOwner already. – Stale

@Stale my app is build on Api 19. – Mme

Okay, so what Fragments are you using? Support Library Fragments support back to API 14 – Stale

@Stale I use androidx.fragment.app – Mme

Then they already implement LifecycleOwner as per the documentation. – Stale

@Stale thanks – Mme

Answer 1

Update: Actually it is better to use getViewLifeCycleOwner if you are using views in your observers. Because the view might not exist when the LiveData gets updated and you want to change the view(e.g. changing visibility of a view) which causes crashes.

The fragment itself is the LifecycleOwner you are looking for. You can use keyword "this" as a reference to the fragment.

Read this: "Lifecycle is a class that holds the information about the lifecycle state of a component (like an activity or a fragment) and allows other objects to observe this state."

And: "LifecycleOwner is a single method interface that denotes that the class has a Lifecycle."

Teaspoon

getViewLifecycleOwner() not "this" – Markel

Answer 2

In fragments you can use getViewLifecycleOwner() method to get the lifeCycleOwner.

Disconcerted

This should the the answer – Markel