I am new to android and I have a scenario where I want to get get data from multiple api. Let suppose api_a, api_b, api_c, api_d. These api are independent of each other but I want to show data from these api in a mix Recycler View (horizontal and vertical). So I want to make these api call in such a manner so that I can get every api data at a time so that i can display in recycler view. I already using retrofit 2 but for that I had to chain them one by one which is very lengthy and I think this is not a feasible approach. I know little bit about RX JAVA ,but I only know how to make one request at a time. Please help
There are at least 2 ways to achieve this -
1) Using RxJava Zip operator (for parallel requests)
Get all the observables
Observable<ResponseType1> observable1 = retrofit.getApi_a();
Observable<ResponseType2> observable2 = retrofit.getApi_b();
Observable<ResponseType3> observable3 = retrofit.getApi_c();
Zip the observables to get a final observable
Observable<List<String>> result =
Observable.zip(observable1.subscribeOn(Schedulers.io()), observable2.subscribeOn(Schedulers
.io()), observable3.subscribeOn(Schedulers.io()), new Function3<ResponseType1, ResponseType2, ResponseType3, List<String>>() {
@Override
public List<String> apply(ResponseType1 type1, ResponseType2 type2, ResponseType3 type3) {
List<String> list = new ArrayList();
list.add(type1.data);
list.add(type2.data);
list.add(type3.data);
return list;
}
});
now subscribe on the resultant observable
result.observeOn(AndroidSchedulers.mainThread())
.subscribeWith(new Observer<List<String>>() {
@Override
public void onSubscribe(Disposable d) {
}
@Override
public void onNext(List<String> s) {
Log.d(TAG, "s is the list with all the data");
}
@Override
public void onError(Throwable e) {
Log.e(TAG, e.getMessage());
}
@Override
public void onComplete() {
}
});
2) Using RxJava flatMap() operator. (To request serially one after another)
This is simple chaining of requests
List<String> result = new ArrayList<>();
Disposable disposable = retrofit.getApi_a()
.subscribeOn(Schedulers.io())
.flatMap((Function<ResponseType1, ObservableSource<ResponseType2>>) response1 -> {
result.add(response1.data);
return retrofit.getApi_b();
})
.flatMap((Function<ResponseType2, ObservableSource<ResponseType3>>) response2 -> {
result.add(response2.data);
return retrofit.getApi_c();
})
.map(response3 -> {
result.add(response3.data);
return response3;
})
.observeOn(AndroidSchedulers.mainThread())
.subscribeWith(new DisposableObserver<Response3>() {
@Override
public void onNext(Response3 response3) {
Log.d(TAG, "result variable will have all the data");
}
@Override
public void onError(Throwable e) {
Log.e(TAG, e.getMessage());
}
@Override
public void onComplete() {
}
});
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