How to get a result from fragment using Navigation Architecture Component?

Question

Let\'s say that we have two fragments: MainFragment and SelectionFragment. The second one is build for selecting some object, e.g. an integer. Ther

Answer 1

According to Google: you should try to use shared ViewModel. Check below example from Google:

Shared ViewModel that will contain shared data and can be accessed from different fragments.

public class SharedViewModel extends ViewModel {
    private final MutableLiveData selected = new MutableLiveData();

    public void select(Item item) {
        selected.setValue(item);
    }

    public LiveData getSelected() {
        return selected;
    }
}

MasterFragment that updates ViewModel:

public class MasterFragment extends Fragment {

    private SharedViewModel model;

    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        model = ViewModelProviders.of(getActivity()).get(SharedViewModel.class);
        itemSelector.setOnClickListener(item -> {
            model.select(item);
        });
    }
}

DetailsFragment that uses shared ViewModel:

public class DetailFragment extends Fragment {
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        SharedViewModel model = ViewModelProviders.of(getActivity()).get(SharedViewModel.class);
        model.getSelected().observe(this, item -> {
           // Update the UI.
        });
    }
}