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() {
}
});
For combining multiple Observables you may want to consider the Merge operator.
This would allow you to combine the stream of multiple requests into a single Observable.
Merge will interleave them as they are emitted. If sequence matters, there is also Concat which will emit from each Observable before continuing with the next.
Rx Doc
Merge: http://reactivex.io/documentation/operators/merge.html
Concat: http://reactivex.io/documentation/operators/concat.html
Merge operator combines multiple observable into one
Set up Base URL of API:
Retrofit retrofit = new Retrofit.Builder()
.baseUrl(Constants.BASE_URL)
.addConverterFactory(GsonConverterFactory.create())
.addCallAdapterFactory(RxJava2CallAdapterFactory.create())
.client(oktHttpClient.build())
.build();
Now setup two observables for the two network requests:
Observable<JsonElement> Observable1 = ApiClient.getApiService().getApi_1();
Observable<JsonElement> Observable2 = ApiClient.getApiService().getApi_2();
Now we use RxJava's mergemethod to combine our two Observables:
Observable.merge(Observable1, Observable2 )
.subscribeOn(Schedulers.io())
.observeOn(AndroidSchedulers.mainThread())
.subscribe(new Observer<JsonElement>() {
#Override
public void onSubscribe(Disposable d) {
}
#Override
public void onNext(JsonElement value) {
Log.d("RESPONSE", "onNext:=======" + value);
}
#Override
public void onError(Throwable e) {
}
#Override
public void onComplete() {
Log.d("RESPONSE", "DONE==========");
}
});
Related
I am trying to send an io.reactivex.Flowable from a Spring RestController to an Android application that uses Retrofit and Rxjava. If I use the browser to check what the Rest endpoint returns, I get a series of values as expected but in Android I get only one value and then it calls the onComplete method. What am I missing?
Spring Controller:
#GetMapping("/api/reactive")
public Flowable<String> reactive() {
return Flowable.interval(1, TimeUnit.SECONDS).map(sequence -> "\"Flowable-" + LocalTime.now().toString() + "\"");
}
Retrofit repository:
#GET("reactive")
Flowable<String> testReactive();
Main service:
public useReactive() {
Retrofit retrofit = new Retrofit.Builder()
.baseUrl(Values.BASE_URL)
.addConverterFactory(JacksonConverterFactory.create())
.addCallAdapterFactory(RxJava2CallAdapterFactory.create())
.build();
userRepository = retrofit.create(UserRepository.class);
Flowable<String> reactive = userRepository.testReactive();
Disposable disp = reactive.subscribeOn(Schedulers.io())
.observeOn(AndroidSchedulers.mainThread())
.subscribeWith(new ResourceSubscriber<String>() {
#Override
public void onNext(String s) {
logger.log(Level.INFO, s);
Toast.makeText(authActivity, s, Toast.LENGTH_SHORT).show();
}
#Override
public void onError(Throwable t) {
t.printStackTrace();
}
#Override
public void onComplete() {
logger.log(Level.INFO, "Completed");
Toast.makeText(authActivity, "Completed", Toast.LENGTH_SHORT).show();
}
});
}
Upon calling the useReactive() method, I get only one value "Flowable-..." and then "Completed".
Even though the Retrofit service has return type Flowable<String>, calling testReactive() will only make one HTTP call on the Android device.
The type Flowable is merely for compatibility, in practice it will end up being a Flowable that emits a single value and then terminates.
This is just how Retrofit works.
You would need to find another solution if you want to continually receive new values that are being emitted from the server, perhaps GRPC or polling the server.
I want to implement a logic using RxJava in my android application, which requires three parallel api calls. Only the third api call has a retry logic. If, after having three attempts, the success is achieved then a subsequent call will be made for the fourth api, else only the result of first and second api calls will be passed on to the subscriber.
I tried to achieve this using Zip operator but then got stuck with retry logic for third api call.
Observable<String> observable1 = Observable.just("A","B");
Observable<Integer> observable2 = Observable.just(1,2);
Observable<Boolean> observable3 = Observable.just(Boolean.TRUE, Boolean.FALSE);
Observable.zip(observable1, observable2, observable3, new Function3() {
#Override
public Object apply(String s, Integer integer, Boolean aBoolean) throws Exception {
if (aBoolean==null){
alphabets3.retry(3).doOnComplete(new Action() {
#Override
public void run() throws Exception {
// the result will never be used
}
});
}
return s+integer+aBoolean;
}
}).subscribe(new Observer<Object>() {
#Override
public void onSubscribe(Disposable d) {
}
#Override
public void onNext(Object o) {
Log.e("onNext-->", o.toString());
}
#Override
public void onError(Throwable e) {
}
#Override
public void onComplete() {
}
});
if any Observable failed in the Zip operator, Zip will fail the stream, the only way I know to achieve parallel execution and error handling with Zip, is to add onErrorResumeNext to each Observable, that map the error to a new model to deal with later .. and handling what you want to do in the zip mapping function ... for example
Obsevable.zip(
observable1.onErrorResumeNext{Observable.just(Model(it)},
observable2.onErrorResumeNext{Observable.just(Model(it)},
observable3.retryWhen {t is TimeOutException} //here you can add your retry logic
.onErrorResumeNext(t -> Observable.just(Model(t)),(m1 , m2, m3) -> Result())
I'm currently trying to use RxJava with Retrofit for the first time but can't seem to get anything working for my specific use case:
I begin by calling an API using retrofit to show cinemas near a users location.
I then use the cinema id which the user clicks on to display showtimes for this cinema i.e...
public interface ListingApiService
{
#GET("/get/times/cinema/{id}")
Call<ListingResponse> getShowtimes (#Path("id") String id);
}
Then using the interface....
public void connectAndGetApiData(String id)
{
if (retrofit == null) {
retrofit = new Retrofit.Builder()
.baseUrl(BASE_URL)
.addConverterFactory(GsonConverterFactory.create())
.build();
}
ListingApiService listingApiService = retrofit.create(ListingApiService.class);
Call<ListingResponse> call = listingApiService.getShowtimes(id);
call.enqueue(new Callback<ListingResponse>() {
#Override
public void onResponse(Call<ListingResponse> call, Response<ListingResponse> response)
{
List<Listing> listings = response.body().getListings()
getAndDisplayImage(listings.get(0).getTitle());
recyclerView.setAdapter(new ListingAdapter(listings,R.layout.list_item_listing,getApplicationContext()));
}
#Override
public void onFailure(Call<ListingResponse> call, Throwable t)
{
Log.e(TAG,t.toString());
}
});
}
I then want to call a different API (contextual web search) to display an image of a relevant movie poster (just for a nice visual effect) for each movie listing. I know how to call the API for a single image, but I don't know how to make multiple calls. I've tried using RxJava code found elsewhere on the internet but none of it seems to work as I don't have prior knowledge of how many calls I will be making or what the search term will be. The code i'm using for a single call is:
public interface ListingImageApiService
{
//https://contextualwebsearch-websearch-v1.p.mashape.com/api/Search/ImageSearchAPI?count=1&autoCorrect=false&q=Donald+Trump
#Headers("X-Mashape-Key: apikey")
#GET("/api/Search/ImageSearchAPI?count=5&autoCorrect=false")
Call<ListingImageResponse> getListingImages (#Query("q") String term);
}
public void getAndDisplayImage(String search)
{
if (retrofit2 == null)
{
retrofit2 = new Retrofit.Builder()
.baseUrl(BASE_URL2)
.addConverterFactory(GsonConverterFactory.create())
.build();
}
search = search + " poster";
ListingImageApiService listingImageApiService = retrofit2.create(ListingImageApiService.class);
Call<ListingImageResponse> call = listingImageApiService.getListingImages(search);
call.enqueue(new Callback<ListingImageResponse>() {
#Override
public void onResponse(Call<ListingImageResponse> call, Response<ListingImageResponse> response)
{
System.out.println(response.body().toString());
ListingImage a = new ListingImage();
List<ListingImage> listingImages = response.body().getListingImage();
System.out.println(listingImages.get(0).getUrl());
}
#Override
public void onFailure(Call<ListingImageResponse> call, Throwable t)
{
}
});
}
My question is, how would I use RxJava to make multiple calls using data for the list of movie titles of unknown size (which I can pass to getAndDisplayImage instead of a single string)? I have made several attempts but none seem to work for my use case. Thank you.
This design should solve your problem.
This interface contains the endpoints used in the application.
public interface ListingApiService
{
#GET("/get/times/cinema/{id}")
Observable<List<MovieResponse>> getShowtimes (#Path("id") String id);
#Headers("X-Mashape-Key: apikey")
#GET("/api/Search/ImageSearchAPI?count=5&autoCorrect=false")
Observable<ListingImageResponse> getListingImages (#Query("q") String term);
}
Method which provides the retrofit object to make the call
private API getAPI() {
Retrofit retrofit = new Retrofit.Builder()
.baseUrl("<your API endpoint address")
.addConverterFactory(GsonConverterFactory.create())
.addCallAdapterFactory(RxJava2CallAdapterFactory.create())
.build();
return retrofit.create(API.class);
}
Make the call to get the List<MovieResponse>. This method also converts the List into a individual observable MovieResponse object.
private void getMovieListingsWithImages() {
Observer<MovieResponse> observer = new Observer<MovieResponse>() {
#Override
public void onSubscribe(Disposable d) {
Toast.makeText(getApplicationContext(), "", Toast.LENGTH_SHORT).show();
}
#Override
public void onNext(MovieResponse movieResponse) {
//for each movie response make a call to the API which provides the image for the movie
}
#Override
public void onError(Throwable e) {
Toast.makeText(getApplicationContext(), "Error getting image for the movie", Toast.LENGTH_SHORT).show();
}
#Override
public void onComplete() {
Toast.makeText(getApplicationContext(), "Finished getting images for all the movies in the stream", Toast.LENGTH_SHORT).show();
}
};
getAPI().getShowtimes()
.flatMapIterable(movieResponseList -> movieResponseList) // converts your list of movieResponse into and observable which emits one movieResponse object at a time.
.flatMap(this::getObservableFromString) // method converts the each movie response object into an observable
.subscribeOn(Schedulers.io())
.observeOn(AndroidSchedulers.mainThread())
.subscribe(observer);
}
method which converts the MovieResponse object into an Observable.
private Observable<MovieResponse> getObservableFromString(MovieResponse movieResponse) {
return Observable.just(movieResponse);
}
I use RxAndroid library + Retrofit2.
I Have 2 post requests:
Get all category (return List == each String is category id)
Get ProductsByCategory (return List)
I need load all products and save to DB after start App.
When I create MainFragment I get all Categories:
restApiFactory.getProductService().getCategories(new CategoryRequest(initiatorId))
.subscribeOn(Schedulers.io())
.observeOn(AndroidSchedulers.mainThread())
.subscribe(new CategoriesHandler());
and Handle response:
#Override
public void onNext(CategoryResponse value) {
List<CategoryItem> categoryItems = value.getCategoryItems();
...
}
And then I need send another request(ProductsByCategory ) but I not understand how do it?
I can send it in foreach:
for (CategoryItem categoryItem : categoryItems) {
Observable<Products> product = ProductsByCategory...
}
or maby there is some Observable merge ....
I do not know. In general, how to do this? two requests to the server. one will return the list of id and the second product on these id.
You can achieve this by using flaMap in rxjava
This is example demonstrate snippet how to implement it
api.serviceA()
.flatMap(new Func1<FooA, Observable<FooB>>() {
#Override
public Observable<FooB> call(FooA fooA) {
// code to save data from service A to db
// call service B
return api.serviceB();
}
})
.subscribeOn(Schedulers.io())
.observeOn(AndroidSchedulers.mainThread())
.subscribe(new Subscriber<FooB>() {
#Override
public void onCompleted() {
}
#Override
public void onError(Throwable e) {
}
#Override
public void onNext(FooB fooB) {
// code to save data from service B to db
}
});
You can use an Iterable, call api with CategoryItem and then use toList() in order to obtain a list of ProductsByCategory.
What I want
I wanted to call a
1 webservice that uploads photo to the server and returns the uploaded link.
2 webservice to save the returned link by 1st webservice.
I wanted to combine two observables and get results as same time
My doubt
What happens if my 1st webservice gets fired successfully and 2nd has encountered an error (eg: Network error, Server error etc)
How can I detect that ? and only retry the 2nd webservice
What I can't do
I can't retry both webservice if 2nd one fails, because I will end up in sending duplicate files for the 1st webservice.
My code
// Upload file (photos,documents etc ):
#POST("some link")
#FormUrlEncoded
Observable<UploadFile> uploadFile(#FieldMap HashMap<String, Object> fields);
// Save link (photos,documents etc ):
#POST("some link")
#FormUrlEncoded
Observable<SaveLink> saveLink(#FieldMap HashMap<String, Object> fields);
// Upload file
Observable<UploadFile> observable = retrofitService.uploadFile(map);
subscriptionUploadFile = observable.observeOn(AndroidSchedulers.mainThread())
.subscribeOn(Schedulers.io())
.subscribe(new Subscriber<UploadFile>() {
#Override
public void onCompleted() {
CommonFunction.printDebug(TAG, "completed");
}
#Override
public void onError(Throwable e) {
}
#Override
public void onNext(UploadFile model) {
}
});
// Save link
Observable<SaveLink> observable = retrofitService.saveLink(map);
subscriptionSaveLink = observable.observeOn(AndroidSchedulers.mainThread())
.subscribeOn(Schedulers.io())
.subscribe(new Subscriber<SaveLink>() {
#Override
public void onCompleted() {
CommonFunction.printDebug(TAG, "completed");
}
#Override
public void onError(Throwable e) {
}
#Override
public void onNext(SaveLink model) {
}
});
Dependent continuation is typically done via flatMap where you can apply retry to the second Observable:
uploadFile(map)
.subscribeOn(Schedulers.io())
.flatMap(file -> {
map.put("URL", file.getURL());
return saveLink(map).retry(10);
})
.observeOn(AndroidSchedulers.mainThread())
.subscribe(...);