How to pass data between fragments

Question

Im trying to pass data between two fragmens in my program. Its just a simple string that is stored in the List. The List is made public in fragments A, and when the user cli

Answer 1

1- The first way is define an interface

public interface OnMessage{
    void sendMessage(int fragmentId, String message);
}

public interface OnReceive{
    void onReceive(String message);
}

2- In you activity implement OnMessage interface

public class MyActivity implements OnMessage {
   ...
   @Override
   public void sendMessage(int fragmentId, String message){
       Fragment fragment = getSupportFragmentManager().findFragmentById(fragmentId);
       ((OnReceive) fragment).sendMessage();
   }
}

3- In your fragment implement OnReceive interface

public class MyFragment implements OnReceive{
    ...
    @Override
    public void onReceive(String message){
        myTextView.setText("Received message:" + message);
    }
}

This is the boilerplate version of handling message passing between fragments.

Another way of handing data passage between fragments are by using an event bus.

1- Register/unregister to an event bus

@Override
public void onStart() {
    super.onStart();
    EventBus.getDefault().register(this);
}

@Override
public void onStop() {
    EventBus.getDefault().unregister(this);
    super.onStop();
}

2- Define an event class

public class Message{
    public final String message;

    public Message(String message){
        this.message = message;
    }
}

3- Post this event in anywhere in your application

EventBus.getDefault().post(new Message("hello world"));

4- Subscribe to that event to receive it in your Fragment

@Subscribe(threadMode = ThreadMode.MAIN)
public void onMessage(Message event){
    mytextview.setText(event.message);
}

For more details, use cases, and an example project about the event bus pattern.