How to cancel individual network request in Retrofit with RxJava?

Question

I am downloading some files from the network using retrofit and rxjava. In my app, the user may cancel the download.

Pseudo Code:

   Subscription subscription = Observable.from(urls)
            .concatMap(this::downloadFile)
            .subscribe(file -> addFileToUI(file), Throwable::printStackTrace);

Now, If I unsubscribe this subscription, then all requests get canceled. I want to download one by one, that's why used concatMap. How do I cancel particular request?

You will have to change your code, so that you have a separate subscription object per URL, which you then can cancel. — Ridcully, Dec 16 '17 at 10:11

akarnokd · Accepted Answer · 2017-12-16T12:05:30.233

3

There is a mechanism to cancel individual flows by external stimulus: takeUntil. You have to use some external tracking for it though:

ConcurrentHashMap<String, PublishSubject<Void>> map =
     new ConcurrentHashMap<>();


Observable.from(urls)
.concatMap(url -> {
    PublishSubject<Void> subject = PublishSubject.create();
    if (map.putIfAbsent(url, subject) == null) {
        return downloadFile(url)
            .takeUntil(subject)
            .doAfterTerminate(() -> map.remove(url))
            .doOnUnsubscribe(() -> map.remove(url));
    }
    return Observable.empty();
})
.subscribe(file -> addFileToUI(file), Throwable::printStackTrace);

// sometime later

PublishSubject<Void> ps = map.putIfAbsent("someurl", PublishSubject.create());
ps.onCompleted();

edited Dec 16 '17 at 12:05

answered Dec 16 '17 at 11:50

akarnokd

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I could not find doFinally. – krupal.agile Dec 16 '17 at 12:00
Right, you are still on 1.x. Updated my answer. – akarnokd Dec 16 '17 at 12:05
Thanks. How do I determine later in "sometime later"? – krupal.agile Dec 16 '17 at 12:07
1

You wanted to cancel individual downloads, so I guess you already had GUI and infrastructure to do just that: a button in a list of urls or what not. – akarnokd Dec 16 '17 at 12:23

How to cancel individual network request in Retrofit with RxJava?

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