How do you do continuations with RxJava Observables?

android, java, rx-android, rx-java

Solution

I think you need API flatMap

eg:

Observable.create(new Observable.OnSubscribe<String>() {
        @Override
        public void call(Subscriber<? super String> subscriber) {
            subscriber.onNext("imageUrl");
        }
    }).flatMap(new Func1<String, Observable<Bitmap>>() {
        @Override
        public Observable<Bitmap> call(String imageUrl) {
            return getBitmapAsync(imageUrl);
        }
    }).subscribe(new Action1<Bitmap>() {
        @Override
        public void call(Bitmap o) {
            imageView.setImageBitmap(image);
        }
    });

Problem

So I have one async operation `A` that depends on a second, `B`. How do I make B a continuation of A as you would have with the then function Javascript Promises, or with ContinueWith in .NET TPL? Let's take a scenarion from Android where I have two service endpoints: - One for fetching a URL for an image - One for fetching the image itself Code: ``` private void loadImage(final ImageView imageView) { Observable<String> stringObs = getImageUrlAsync(); stringObs.subscribe(new Action1<String> () { @Override public void call(String imageUrl) { // First async operation done Observable<Bitmap> bitmapObs = getBitmapAsync(imageUrl); bitmapObs.subscribe(new Action1<Bitmap>() { @Override public void call(Bitmap image) { // second async operation done imageView.setImageBitmap(image); } }); } }); } ``` I would like not to have these two operations nested code-wise, but be in a format that reads more like it acts - sequentially. I've been unable to find anything about continuations with regards to Observables in RxJava/RxAndroid. Can anyone please help?

Original source