View of a Fragment becoming null at the time of onSaveInstanceState() callback

Question

I have a Fragment(used support library) like this

public class ItemDetailsFragment extends Fragment {
    private ListView itemsListView;

    @Override
    public void onViewCreated(View view, Bundle savedInstanceState) {
        super.onViewCreated(view, savedInstanceState);
        itemsListView = (ListView) view.findViewById(R.id.listMode);
    }

    @Override
    public void onSaveInstanceState(Bundle outState) {
        super.onSaveInstanceState(outState);
        ItemsAdapter adapter = (ItemsAdapter) itemsListView.getAdapter();
        ArrayList<String> items = adapter.getItems();
        outState.putStringArrayList("some_key", items);
    }
}

Note that itemsListView is initialized properly. and when I set Adapter to this ListView, ListView is showing items properly. but when I call

 itemsListView.getAdapter();

in onSaveInstanceState callback, I am getting NPE and I recognized that itemsListView is null while debugging. I am confident that I am not assigning itemsListView to null through out the Fragment. More over, I am getting this NPE error only sometimes but I am unable to say when it is.

Where the error might be? why itemsListView is becoming null only some times?

Thanks to all...

Answer 1

There is a note in Android documentation on onSaveInstanceState fragments:

This corresponds to Activity.onSaveInstanceState(Bundle) and most of the discussion there applies here as well. Note however: this method may be called at any time before onDestroy(). There are many situations where a fragment may be mostly torn down (such as when placed on the back stack with no UI showing), but its state will not be saved until its owning activity actually needs to save its state.

It makes using onSaveInstanceState methods for fragments rather tricky.