How to send event from Service to Activity with Otto event bus?

Question

Simple BusProvider.getInstance().post() bring exception not main thread. How to send event from Service to Activity with Otto event bus?

Answer 1

To post from any thread (main or background) and receive on the main thread, try something like

public class MainThreadBus extends Bus {
  private final Handler mHandler = new Handler(Looper.getMainLooper());

  @Override
  public void post(final Object event) {
    if (Looper.myLooper() == Looper.getMainLooper()) {
      super.post(event);
    } else {
      mHandler.post(new Runnable() {
        @Override
        public void run() {
          MainThreadBus.super.post(event);
        }
      });
    }
  }
}

Note: credit goes to Jake Wharton and "pommedeterresaute" at https://github.com/square/otto/issues/38 for the general approach. I just implemented it with a wrapper class rather than a subclass.

Answer 2

To post from any thread (main or background) and receive on the main thread, use the following MainThreadBus instead of a vanilla Bus

public class MainThreadBus extends Bus {
     private final Handler handler = new Handler(Looper.getMainLooper());

     @Override public void post(final Object event) {
        if (Looper.myLooper() == Looper.getMainLooper()) {
            super.post(event);
        } else {
            handler.post(new Runnable() {
                @Override
                public void run() {
                    MainThreadBus.super.post(event);
                }
            });
        }
    }
}

This is based on Andy Dennie's answer.

There is no need to both extend and wrap a Bus object, do one or the other. In Dennie's answer, which is effectively a wrapper, the Bus base class is just being used like an interface, all the functionality is overwritten.

It would work even if you removed the Bus base class unless you happened to reference the MainThreadBus via a Bus reference.

Answer 3

Or simply do this if you're sure that you're posting from a Non-main thread:

new Handler(Looper.getMainLooper()).post(new Runnable() {
                    @Override
                    public void run() {
                        mBus.post(new myEvent());
                    }
                });

Just as the saying goes, "Keep It Simple and Stupid" :)

Answer 4

bus = new Bus(ThreadEnforcer.ANY); is the clear solution to this problem. Its all you have to do.

Answer 5

Best implementation custom bus class for me

public class AndroidBus extends Bus {
    private final Handler mainThread = new Handler(Looper.getMainLooper());

    @Override
    public void post(final Object event) {
        if (Looper.myLooper() == Looper.getMainLooper()) {
            super.post(event);
        } else {
            mainThread.post(() -> AndroidBus.super.post(event));
        }
    }
}

Answer 6

I did it simply:

Handler handler = new Handler(Looper.getMainLooper());
        handler.post(new Runnable() {
            @Override
            public void run() {
                bus.post(event);
            }

        });

Happy coding.. :)

Answer 7

Just create the BasicBus with ThreadEnforcer.NONE to post event from non-main threads. The mentioned ThreadEnforcer.MAIN is exactly the opposite (and the default), which accepts only posts from the main-thread.