Android 侦听器在活动中工作但不在片段中

Question

I have an activity and two fragments. Im trying to get a clicked item from an arraylist. In my fragmentA I have a interface:

public interface GroupListener {
        public String onGroupSelected(String groupName);
}

and

    @Override
    public void onAttach(@NonNull Context context) {
        super.onAttach(context);

        try {
            groupListener = (GroupListener) context;
        } catch (ClassCastException e)
        { 
            throw new ClassCastException(context.toString() + " must implement the interface" +
                    "called GroupListener!");
        }
    }

This gets the postion from an item clicked in a list:

    public void onListItemClick(@NonNull ListView l, @NonNull View v, int position, long id) {
        groupListener.onGroupSelected((String) getListAdapter().getItem(position));
    }

I then have the listner in my activity and in fragmentB which looks the same:

   @Override
    public String onGroupSelected(String groupName) {
        System.out.println("in onGroup  in Activity");
        return groupName;
    } 

   @Override
    public String onGroupSelected(String groupName) {
        System.out.println("in onGroup  in fragmentB");
        return groupName;
    } 

But when i click an item only the listener in my activity is activated, not the one in my fragment. What is it that im missing?

Answer 1

The one in FragmentB will not fire, since you are only communicating with the activity from fragment A.

In your activity do something like this:

Override
    public String onGroupSelected(String groupName) {
        System.out.println("in onGroup  in Activity");
        FragmentB frag = //find your fragment using fragment manager
        frag.onGroupSelected(groupName);
        return groupName;
    } 

This is how you call methods inside fragment from an activity

Answer 2

It is a little late to answer but I found a way that works for me. As listener will first get by activity, you can define destination fragment in the Main activity and then call a method in the destination fragment and do what you want:
In the main Activity listener

DestinationFragment fragment = (DestinationFragment) getSupportFragmentManager().findFragmentById(R.id.destination_fragment);
fragment.sampleListener(bundle);

In the destination fragment define sampleListener and write your code.