BusUtil.java

package YOUR_PACKAGE;

import android.os.Handler;
import android.os.Looper;
import com.squareup.otto.Bus;

public class BusUtil
{
    private static final Handler mainThread = new Handler(Looper.getMainLooper());

    /**
     * making sure your bus update goes into the main thread
     * @see <a href="http://square.github.io/otto/" target="_blank">Otto</a>
     **/
    public static void postOnMain( final Bus bus, final Object event) {

        mainThread.post(new Runnable() {
            @Override
            public void run() {
                bus.post(event);
            }
        });
    }
}