@Override
    public void onDetach() {
        super.onDetach();

        // Reset the active callbacks interface to the dummy implementation.
        mCallbacks = sDummyCallbacks;
    }
Mandatory empty constructor for the fragment manager to instantiate the
fragment (e.g. upon screen orientation changes).
Example/src/com/tonicartos/stickygridheadersexample/ItemListFragment.java