Is there any way to get a Scheduler from OnSubscribe function?

Hello.

My Observable is very simple and looks like:

Observable.create(new Observable.OnSubscribe<Content>() {
    @Override
    public void call(final Subscriber<? super Content> subscriber) {
        final ContentObserver observer = new ContentObserver() {
            @Override
            public void onContentChanged() {
                subscriber.onNext(loadContent());
            }
        };

        subscriber.add(Subscriptions.create(new Action0() {
            @Override
            public void call() {
                unregisterContentObserver(observer);
            }
        }));

        registerContentObserver(observer);
        subscriber.onNext(loadContent());
    }
});

loadContent is a heavy operation and have to be executed on the background thread (which is provided by the Scheduler that I pass to subscribeOn method).

PROBLEM onContentChanged is always invoked from the UI thread and this cannot be changed, so I need to reschedule loadContent call to the background thread, but I failed to find a way to get a current Scheduler.

What is the right way to do it?

[Ghedeon]

I think @benjchristensen nailed it. I believe Schedulers.current() could be very useful for wrapping some non-rx code that is switching threads for some reason. Happens on Android often, when callback is called on main thread. Consider this example:

private static class MyOnSubscribe implements ObservableOnSubscribe<Foo> {
    @Override
    public void subscribe(ObservableEmitter<Foo> emitter) throws Exception {
        // worker thread
        callbackManager.registerCallback( //some sdk method that always delivers on main
                new Callback() {
                    @Override
                    public void onSuccess(@NonNull Foo result) {
                        // Main Thread. How to move onSuccess() back to worker?
                        emitter.onSuccess(result);
                    }
                }
         ...
        );
    }
}

Yes, I can just leave it as it is, let it deliver on main and fix it later with observeOn. But it just feels right to do it here, rather than outside.

EDIT: onSubscribe --> observeOn

[lwasyl]

Sorry for digging up the thread, but we’re facing the same issue as OP – callback is called on a different thread than the subscription, and we’d like to emit value on the original subscribeOn scheduler anyway. Did anything change with RxJava2? I don’t believe https://github.com/ReactiveX/RxJava/issues/941#issuecomment-125480042 is sufficient if we really care about going back to the same scheduler without having to inject it manually. I can also open a new issue if that’s more appropriate