android - How to communicate between two child Fragments inside a Nested Fragment -

i can communicate between 2 fragments of activity callback interface. following way, have implemented interface in parentfragment communicate.

but in case of activity, using -

 @override     public void onattach(activity activity) {         super.onattach(activity);         try {             mcallback = (onheadlineselectedlistener) activity;         } catch (classcastexception e) {             throw new classcastexception(activity.tostring()                     + " must implement onheadlineselectedlistener");         }     } 

and in current case, using mcallback = (onheadlineselectedlistener) getparentfragment(); instead of mcallback = (onheadlineselectedlistener) activity;. working well. approach okay? or should thread instead onattach()?

the cast thing ensure object instance of class implements given interface (in case onheadlineselectedlistener). it's irrelevant @ point type of object activity, fragment or else. long implements interface need, fine.