RxJava 2 creates lists in a new thread
Developers!
I’m trying to use RxJava in a real project, but it seems I’m not understanding the correct logic. I need to create a list of objects in a new thread. Send this list to the observer when finished. What I found is:
LinkedList<IntroSliderElement> list = new LinkedList<>();
list.add(new IntroSliderElement(0, "test 0", 0));
list.add(new IntroSliderElement(1, "test 1", 1));
list.add(new IntroSliderElement(2, "test 2", 2));
Observable<LinkedList<IntroSliderElement>> listObserv = Observable.just(list);
listObserv
.subscribeOn(Schedulers.io())
.observeOn(AndroidSchedulers.mainThread())
.subscribe(new Observer<List<IntroSliderElement>>() {
@Override
public void onSubscribe(Disposable d) {
}
@Override
public void onNext(List<IntroSliderElement> value) {
view().render(new IntroModel.OnFirstSliderElement((LinkedList<IntroSliderElement>) value));
}
@Override
public void onError(Throwable e) {
}
@Override
public void onComplete() {
}
});
But it’s easy to see that list is created and executed in the main thread, so how do you create it in a whole new thread using rxJava?
Solution
What you want is probably Observable.fromCallable() .
Observable.fromCallable(() -> {
init your list here
yourList = ....
Observable.fromIterable(yourList);
});
The internal code is executed when the subscription occurs.
Thus, you can perform subscriptions on your favorite threads.
Observable.create() will be executed immediately, regardless of whether the subscription occurs or not, which is why it is recommended to use it sparingly.
As Artem Zinnatullin’s post states:
Don’t use Observable.create() if you can, it’s very easy to shoot yourself in the foot! (and then shoot again for each new subscriber!)