Return Callable from retrofit method on android

Question

This is my method on Retrofit:

@GET("comments")
Callable<List<Comments>> getCommentsRx();

I have created Thread class for Rxjava stuff :

public static <T> Disposable async(Callable<List<T>> task, Consumer<List<T>> finished, Consumer<Throwable> onError) {
        return async(task, finished, onError, Schedulers.io());
    }

public static <T> Disposable async(Callable<List<T>> task, Consumer<List<T>> finished,
                                   Consumer<Throwable> onError, Scheduler scheduler) {
    finished = finished != null ? finished
            : (a) -> {
    };
    onError = onError != null ? onError
            : throwable -> {
    };

    return Single.fromCallable(task)
            .subscribeOn(scheduler)
            .observeOn(AndroidSchedulers.mainThread())
            .subscribe(finished, onError);
}

I have loadjson method to fetch data from network:

private void loadJson(Consumer<List<Comments>> finished) {

    Threading.async(() -> fetchingServer(),finished,null);
}

private List<Comments> fetchingServer() {
    JsonplaceholderService service =
            ServiceGenerator.createService(JsonplaceholderService.class);

    try {
        return service.getCommentsRx().call();
    } catch (Exception e) {
        e.printStackTrace();
    }
    return null;
}

but i got error in fetchingServer method.

java.lang.IllegalArgumentException: Unable to create call adapter for java.util.concurrent.Callable> for method JsonplaceholderService.getCommentsRx

Answer 1

Retrofit doesn't have adapters for Callable and you can't use it in your @GET method.

You can use:

1. RxJava2 Observable, Flowable, Single, Completable & Maybe,

2. Java 8 CompletableFuture

3. Retrofit Call

So, you can do something like this:

@GET("comments")
Observable<List<Comments>> getCommentsRx(); //rx observable, not java.util.observable

In your client:

  service.getCommentsRx()
        .subscribeOn(scheduler)
        .observeOn(AndroidSchedulers.mainThread())
        .subscribe(finished, onError)