Rxandroid What's the difference between SubscribeOn and ObserveOn

Question

I am just learning Rx-java and Rxandroid2 and I am just confused what is the major difference between in SubscribeOn and ObserveOn.

Answer 1

If someone finds rx java description hard to understand (as me for example), here is pure java explanation:

subscribeOn()

Observable.just("something")
  .subscribeOn(Schedulers.newThread())
  .subscribe(...);

Is equivalent of:

Observable observable = Observable.just("something");
new Thread(() -> observable.subscribe(...)).start();

Because Observable emits values on subscribe() and here subscribe() goes in the separate thread, the values are also emitted in the same thread as subscribe(). This is why it works "upstream" (influences the thread for the previous operations) and "downstream".

observeOn()

Observable.just("something")
  .observeOn(Schedulers.newThread())
  .subscribe(...);

Is equivalent of:

Observable observable = Observable.just("something")
  .subscribe(it -> new Thread(() -> ...).start());

Here Observable emits values in the main thread, only the listener method is executed in the separate thread.