public void onAttach(Activity activity) {
        onAttach(activity);
 
        // This makes sure that the container activity has implemented
        // the callback interface. If not, it throws an exception
        try {
             mListener = (AdapterListener) activity;
        } catch (Exception e) {
             throw new Exception(activity.ToString()
                  + " must implement OnHeadlineSelectedListener");
        }
   }
        /// <summary>
        /// Make sure the activity has implemented OnFragmentUpdateListener
        /// </summary>
        /// <param name='activity'>
        /// Our activity
        /// </param>
        public override void OnAttach(Activity activity)
        {
            base.OnAttach(activity);

            try
            {
                mCallback = activity as OnFragmentUpdateListener;
            }
            catch(InvalidCastException ex)
            {
                throw new InvalidCastException(activity.ToString() + " must implement OnFragmentUpdateListener");
            }
        }