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?

By default Otto uses the MAIN thread (see thread enforcement: http://square.github.com/otto/). Are you trying to post FROM another thread? Include example code and your stack trace. — Charlie Collins, Mar 15 '13 at 12:18
Another way of achieving this is to use `runOnUiThread`, provided there is access to an Activity. Not very clean but will do the job. — ticofab, Jun 18 '15 at 10:55

score 122 · Accepted Answer · edited Jan 04 '17 at 23:25

122

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.

edited Jan 04 '17 at 23:25

Victor Häggqvist

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answered Mar 15 '13 at 13:09

Andy Dennie

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3

Thanks. So as of now, does **Bus bus2 = new Bus(ThreadEnforcer.MAIN);** resolve it? – Thuy Trinh Feb 28 '14 at 16:27
3

For me `ThreadEnforcer.MAIN` did not resolve it, but the code provided here. – Konrad Reiche May 20 '14 at 09:16
@platzhirsch from the doc: _If you are not concerned on which thread interaction is occurring, instantiate a bus instance with ThreadEnforcer.ANY_ – gderaco Jul 06 '14 at 15:31
@gdrc Thanks for catching up on this. After looking into the source code it became clear. I thought `ThreadEnforcer.ANY` is the default. – Konrad Reiche Jul 06 '14 at 17:57
2

Why are you using a wrapper and a subclass? Very confusing. – Matt Logan Oct 28 '14 at 20:54
Any idea if this would work on a `Wear` device using `WearableListenerService`? – theblang Oct 29 '14 at 00:55
why isn't this built into the library? Its a pretty common use case. – stevebot Jan 20 '15 at 21:58
Not sure, but this code causes an out of memory error for me. – Simon Aug 21 '15 at 19:03
what is best approach to handle if `event` is null? – Hesam Oct 05 '15 at 17:11

score 20 · Answer 2 · edited Apr 11 '14 at 13:14

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.

My answer implemented an interface which was part of Otto at the time, but has since been removed (and someone edited my answer to make it extend rather than implement); that's why it looks odd now. In my example I wanted to wrap another bus that was not limited to being used on the main thread only. — Andy Dennie, Apr 29 '14 at 19:03

score 3 · Answer 3 · edited Dec 08 '21 at 12:25

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());
                    }
                });

edited Dec 08 '21 at 12:25

Nimantha

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answered Nov 25 '16 at 04:06

Jiyeh

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score 2 · Answer 4 · answered Apr 04 '16 at 10:55

2

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

answered Apr 04 '16 at 10:55

drlobo

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score 0 · Answer 5 · answered Apr 14 '16 at 10:31

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));
        }
    }
}

score 0 · Answer 6 · edited Dec 08 '21 at 12:15

0

I did it simply:

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

        });

edited Dec 08 '21 at 12:15

Nimantha

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answered Jan 19 '17 at 14:01

Shailendra Madda

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score -1 · Answer 7 · answered Apr 22 '15 at 21:55

-1

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.

answered Apr 22 '15 at 21:55

Carsten

1

1

It's unlikely that this is a usable answer. The OP says "... to Activity ...", which implies to me that the processing needs to be done on the UI or main thread. – RenniePet Nov 22 '15 at 06:33

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

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