Combine data from multiple API calls using retrofit and RxJava (Android)

Question

What I'd like to do is access data at a few different URLs, combine this data, and then work with it in my app. I'm having no trouble getting all of the data I need, but what I can't figure out is how to combine the data into a single list and know when all of the API calls are done (all of the data is in the list).

Here's the loop where I make my API calls:

for(String diningCourt: diningCourts){
        menuApi.getMenu(diningCourt, date)
                .subscribeOn(Schedulers.newThread())
                .observeOn(AndroidSchedulers.mainThread())
                .subscribe(responseData -> {

                     //I want to add responseData to a list with 
                     //the results from the rest of the calls 

                });
    }

What's the correct way to collect the data? I've tried using a static class variable to store the results but I only end up with data from one of the API calls. Any suggestions would be greatly appreciated.

Michael Greifeneder · Accepted Answer · 2018-01-02 20:12:13Z

1

We use "combineLatest" see http://reactivex.io/documentation/operators/combinelatest.html With this operator both calls are executed and you get a result, when both calls have finished.

Observable.combineLatest(observable1, observable2, (result1, result2) -> { //use both results })

answered Jan 2, 2018 at 20:12

Michael Greifeneder

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2 Comments

Lucas Over a year ago

I'm having some trouble getting it to work. Is there something I need to do to the observables? Currently I have this and I can't get the print statement to show:

Observable.combineLatest(observables.get(0), observables.get(1), (result1, result2) -> {             System.out.println("HERE");             return null;         });

(where observables is a list of Observable objects generated by the retrofit calls)

Michael Greifeneder Over a year ago

You have to subscribe to the observable. Otherwise the items are not pulled from the source.

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