rxandroid asks to run on ui thread even though it is subscribed on AndroidSchedulers.mainThread()

Question

I have written a subscriber that will get triggered when google map's OnCameraChangeListener is triggered.

Observable.create(new Observable.OnSubscribe<LatLng>()
    {
        @Override
        public void call(Subscriber<? super LatLng> subscriber)
        {
            if (!subscriber.isUnsubscribed())
            {
                mMap.setOnCameraChangeListener(cameraPosition ->
                        subscriber.onNext(cameraPosition.target));
            }
        }
    }).subscribeOn(AndroidSchedulers.mainThread())
            .observeOn(AndroidSchedulers.mainThread())
            .onErrorResumeNext(Observable.<LatLng>empty())
            .debounce(1, TimeUnit.SECONDS)
            .subscribe(position -> {
                if (position.latitude != 0 && position.longitude != 0)
                {
                    updateLocationMarker(position);
                }
            });

I am updating the location marker as below:

private void updateLocationMarker(LatLng center)
{
    locationMarkertext.setText("Lat:" + center.latitude + " Long:" + center.longitude);
    //locationMarkerLayout.setVisibility(View.VISIBLE);
}

Even though my code says to run on AndroidSchedulers.mainThread() I get this error:

Caused by: rx.exceptions.OnErrorNotImplementedException: Only the original thread that created a view hierarchy can touch its views.

Can some one please help me understand what is the problem with my approach

Answer 1

The operator debounce by default runs on the computation scheduler where it will deliver the events flowing through. You have to parameterize it with the main thread scheduler:

.debounce(1, TimeUnit.SECONDS, AndroidSchedulers.mainThread())

In addition, depending on where you create your notification source, you may not need observeOn and subscribeOn at all.