RxAndroid http request in background using retrofit

Question

To better understand RxAndroid I found this Repo which is full of useful examples using RxAndroid, especially in combination with Retrofit.

So if I look at this part of the repo, I can make an http call by clicking an button which seems to be running in the background right?

What if I have this app which needs to show an activity/fragment and at the same time do some http call on the background and show the data if there is any received?

So for instance I have this fragment with onStart

@Override
public void onStart() {
    super.onStart();

    pomagistoService
            .getAgenda()
            .subscribeOn(Schedulers.newThread())    // <- run in background right?
            .observeOn(AndroidSchedulers.mainThread())
            .subscribe(new Observer<List<Appointment>>() {
                @Override
                public void onCompleted() { }

                @Override
                public void onError(Throwable e) { }

                @Override
                public void onNext(List<Appointment> appointments) {
                    // show data in ListView
                }
            });
}

If I start this fragment a ListView instantaneously contains the data which is received by the http call.

Now the question/wondering I have is: Does this http call run in the background?

I am asking this because of the data which is there immediately when the fragment appears, so I can't really observe it.

@AmitShekhar oke, so let's say the http call takes 5seconds, it won't take 5seconds for the fragment to appear? The fragment just appears (without data)? — Jim Vercoelen
@AmitShekhar yeah yeah I know, am doing that! But because of the call is so fast the data is there before the fragment even had the change to show ;-p — Jim Vercoelen

Daniil Yakovlev Daniil Yakovlev · Accepted Answer · 2017-07-14T10:23:36

Usually, for network request you should use not Schedulers.newThread(), but Schedulers.io(). Also, to get some delay before request is executed and get a chance to see fragment without data try to use .delay(5, TimeUnit.SECONDS) to make 5 seconds delay before call.

RxAndroid http request in background using retrofit

2 Answers