Passing interface to Fragment

Question

Let's consider a case where I have Fragment A and Fragment B.

B declares:

public interface MyInterface {     public void onTrigger(int position); } 

A implements this interface.

When pushing Fragment B into stack, how should I pass reference of Fragment A for it in Bundle so A can get the onTrigger callback when needed.

My use case scenario is that A has ListView with items and B has ViewPager with items. Both contain same items and when user goes from B -> A before popping B it should trigger the callback for A to update it's ListView position to match with B pager position.

Thanks.

Answer 1

Passing interface to Fragment 

I think you are communicating between two Fragment

In order to do so, you can have a look into Communicating with Other Fragments

public class FragmentB extends Fragment{     MyInterface mCallback;      // Container Activity must implement this interface     public interface MyInterface {         public void onTrigger();     }      @Override     public void onAttach(Activity activity) {         super.onAttach(activity);          // This makes sure that the container activity has implemented         // the callback interface. If not, it throws an exception         try {             mCallback = (MyInterface ) activity;         } catch (ClassCastException e) {             throw new ClassCastException(activity.toString()                     + " must implement MyInterface ");         }     }      ... } 

Answer 2

For Kotlin 1.0.0-beta-3595

interface SomeCallback {}  class SomeFragment() : Fragment(){      var callback : SomeCallback? = null //some might want late init, but I think this way is safer      override fun onCreateView(inflater: LayoutInflater?, container: ViewGroup?, savedInstanceState: Bundle?): View? {         callback = activity as? SomeCallback //returns null if not type 'SomeCallback'          return inflater!!.inflate(R.layout.frag_some_view, container, false);     } }