Communicate between different instances of same fragment

Question

The problem as follows. Let us have 3 tabs with fragments:

• Tab 1 (Fragment A). Needs to send data to Tab 2.
• Tab 2 (Fragment B). Needs to receive data from Tab 1.
• Tab 3 (Fragment B). Already contains data.

As you see Tab 3 and Tab 2 contain the same Fragment but different instances.

How do I send data (not via arguments) to exactly Tab 2?

What I've tried:

1. Set the unique ID for Fragment B via arguments when they were created.
2. Register same Local Broadcast Receiver for both instances of Fragment B
3. Send data from Fragment A to Fragment B with its ID
4. In Fragment B onReceive() check if recevied ID equals ID of Fragment

But unfortunately broadcast was sent to Tab 3 only.

---

EDIT: some more information.

Those tabs are hosted inside another fragment with ViewPager. Thats due to combination of NavigationDrawer which has fragment with ViewPager and Tabs mentioned in question.

Answer 1

I'd suggest to introduce EventBus in your app.

To add dependency - add compile 'de.greenrobot:eventbus:2.4.0' into your list of dependencies.

Then, you just subscribe your third tab's fragment to listen to event from the first fragment.

Something like this: in Fragment B

@Override
public void onAttach(Activity activity) {
    super.onAttach(activity);
    eventBus.register(this);
}

@Override
public void onDetach() {
    eventBus.unregister(this);
    super.onDetach();
}

@SuppressWarnings("unused") // invoked by EventBus
public void onEventMainThread(NewDataEvent event) {
    // Handle new data
}

NewDataEvent.java

public class NewDataEvent extends EventBase {
    public NewDataEvent() {}
}

And in Fragment A just send the event:

protected EventBus eventBus;
....
eventBus = EventBus.getDefault();
....
eventBus.post(new NewDataEvent());

(and to avoid handling event in 2nd tab - just pass extra parameter during instantiation of fragment, if it has to listen to the event)

Answer 2

Are the fragments hosted in one activity? Then you could implement an interface on your hosting activity.

YourActivity implements MyInterface {
...
}

And in your fragments you define this:

@Override
public void onAttach(final Activity context) {
  myInterface = (MyInterface) context;
}

And when you click something in your fragment then call myInterface.doSomething(parameter);. And then your activity can delegate to another fragment.