Update selected state of navigation drawer after back press

Question

Whats the proper way to handle the selected state of the navigation drawer after back press?

I have a navigation drawer with n entries (in a listview) like the SDK sampl

Answer 1

today I had the same strugle. I solved it by implementing an Interface FragmentToActivity in every Fragment and in my one and only MainActivity.

Interface:

public interface FragmentToActivity {
    public void SetNavState(int id);
}

Fragments:

@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
                         Bundle savedInstanceState) {
    ((FragmentToActivity) getActivity()).SetNavState(R.id.nav_myitemid); //just add this line
}

MainActivity:

@Override
public void SetNavState(int id) {
    NavigationView nav = (NavigationView) findViewById(R.id.nav_view);
    nav.setCheckedItem(id);
}

And if you have no idea, where R.id.nav_myitemid comes from, here is my activity_main_drawer.xml: