android - How to pass result from second fragment to first fragment

Question

In my app I have two fragments say fragmentA and FragmentB. When I click on a button in fragmetA, a list is opened in fragmentB. Now when I select an item from list in fragmentB I want the result to be passed to fragmentA. I am using only one TabActivity for all fragments. When list item is selected in fragmentB I am popping out fragmentB from stack so that I can directly go back to fragmentA.

Does anyone knows how to pass result to previous fragment.

Thanks.

Answer 1

Update

Activity is the parent controller and should take responsibility for handling those events raised by its fragments/views, which concern something outside of the scope of fragment/view itself.

A Fragment is to act as a sub-controller of Views it hosts. All the events and communication between its own views, the fragment should handle itself. When there is an event outside of a fragment's scope and responsibilities (like sending data to another fragment), that event should be escalated to its parent controller, the Activity.

Old

From this tutorial : http://developer.android.com/guide/components/fragments.html#CommunicatingWithActivity

Its better to let the activity apply changes to its fragment than passing values directly between fragments. Let your Activity implement a FragmentListener interface with onQuery(Bundle data) and onResult(Bundle data) methods.

Create a FragmentListener varaible in each of your fragments and then override onAttach() of each fragment as:

 public void onAttach(Activity activity) {
    super.onAttach(activity);

    //---register parent activity for events---
    try{
        fragmentListener = (FragmentListener) activity;
    }catch (ClassCastException e)
    {
        throw new ClassCastException("Parent activity must implement interface FragmentListener.");
    }
  }

This will enforce your child fragments to be automatically registered to parent Activity.

Also, remember to release fragmentListener reference in onDetach().

Now you can call your Activity from fragments.

On the other side, your Activity can always search for a fragment using getFragmentManager().findFragmentByTag("fragmentA") or findFragmentById("FragmentA"). If it can find your Fragment, Then it can cast it into your FragmentA class and call its methods. Same can be done with FragmentB or any other fragment..