Invoke the listener method reference on the current activity

HeadLineFragment.java

  public class HeadLineFragment extends ListFragment {
   @Override
   public void onListItemClick(ListView l, View v, int p, long i) {
     // Send the event to the host activity
     // we should probably check if the activity is finishing|destroyed|rotating
     mCallback.onArticleSelected(getActivity(), p);
   }
  }