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javaandroidgreenrobot-eventbus

EventBus confusion

I'm trying to send a list of objects from ActivityTwo to MainActivity

I have followed EventBus's get started page and called register() and unregister() methods from onStart and onStop, then i used EventBus.getDefault().post() to send the data.

On MainActivity I do not get anything unless I remove the unregister() call from onStop().

My question is, am I using it correctly? should I be calling unregister() in onDestroy()? if so, why are they calling it from onStop if it will not pick up anything if the activity is stopped

MainActivity

@Subscribe(threadMode = ThreadMode.MAIN)
public void onMessageEvent(YoutubeData event) {

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

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

ActivityTwo

private void sendYoutubeData() {
        if(youtubeData != null){

          EventBus.getDefault().post(youtubeData);
          finish();
      }

 }
Solution

  • If you want to receive the event in MainActivity when it's not visible, yes, you should place your register() and unregister() respectively in onCreate() and onDestroy().

    If there's no listeners for your event, it will never be received, EXCEPT if it's a sticky event, in which case you will be able to receive it when registering. More information about Sticky Events here