Use scheduling with RxAndroid

Question

I'm using a RxAndroid observable to retrieve some object (String in this case). My service looks like this:

 public Observable<String> getRandomString() {
    return Observable.create(new Observable.OnSubscribe<String>() {
        @Override
        public void call(Subscriber<? super String> subscriber) {

            //code to retrieve result

            subscriber.onNext("this is a string");
            subscriber.onCompleted();

        }
    });
}

I subscribe in my presenter and post the result to the view:

public void loadRandomString() {

    Observable<String> observable = mService.getRandomString();
    observable
            .observeOn(AndroidSchedulers.mainThread())
            .subscribeOn(Schedulers.newThread())
            .subscribe(new Subscriber<String>() {
                @Override
                public void onCompleted() { }

                @Override
                public void onError(Throwable e) {
                    mMainView.onError(e.getLocalizedMessage());
                }

                @Override
                public void onNext(String string) {

                    //do something with string
                }
            });
}

This works fine and all, but I want this operation to be periodically (every x minutes). I could use a Timer or ScheduledThreadPoolExecutor to do this over and over again but i'd like to see if there is some solution within the realm of RxAndroid. I found some old solutions from 2013 but a lot of the code is deprecated at this time. Is this possible using some kind of recursion, or can I achieve this in a more elegant way?

Thanks in advance!

Answer 1

What you probably want is Observable.interval(). It emits on a timed interval. You can then flatmap that into your Observable<String>, like so:

Observable.interval(3, TimeUnit.MINUTES)
    .flatMap(new Func1<Long, Observable<String>>() {
      @Override
      public Observable<String> call(Long ignore) {
        return getRandomString();
      }
    })
    .subscribe(...insert your subscriber here...);

That said - if you're going to be doing this every few minutes, you might be better off looking into AlarmManager or JobScheduler, since chances are users won't be focused on your app for that long of a period of time.

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As an aside, it'd be much easier to use Observable.just("this is a string") than Observable.create().