public override void OnAttach(Activity activity)
 {
     base.OnAttach(activity);
     try
     {
         mCallbacks = (ListDrawerFragment.IListSelectionCallback)activity;
     }
     catch (InvalidCastException)
     {
         throw new InvalidCastException("Activity must implement NavigationDrawerCallbacks."
                                        );
     }
 }
 public override void OnDetach()
 {
     base.OnDetach();
     mCallbacks = null;
 }
 public override void OnDetach()
 {
     base.OnDetach();
     mCallbacks = null;
 }
 public override void OnAttach(Activity activity)
 {
     base.OnAttach(activity);
     try
     {
         mCallbacks = (ListDrawerFragment.IListSelectionCallback)activity;
     }
     catch (InvalidCastException)
     {
         throw new InvalidCastException("Activity must implement NavigationDrawerCallbacks."
             );
     }
 }