Question

我正在为RxJava2奋斗。我想对列表的每个项目执行功能。此功能：

public void function(final Result result) {

    FirebaseFirestore.getInstance().collection(COLLECTION_NAME).document(result.getId()).get().addOnSuccessListener(new OnSuccessListener<DocumentSnapshot>() {
        @Override
        public void onSuccess(DocumentSnapshot documentSnapshot) {
            // do some operation
        }
    });
}

此功能是异步的，并使用FirebaseFirestore。

因此，我尝试使用列表上的RxJava2来为每个项目调用该函数：

Observable.fromIterable(resultList)
                    .concatMap(result -> Observable.fromCallable(new Callable<String>() {
                        @Override
                        public String call() throws Exception {
                            function(result);
                            return "ok";
                        }
                    }))
                    .subscribe(r -> {
                        // do some operation when all firebase async tasks are done
                    });

concatMap起作用，并且为列表的每个项目调用该函数。问题是当完成所有Firebase异步任务时，我需要回调。

任何帮助将不胜感激。

Answer 1

我将尝试画一个可能的解决方案：

public class Callback implements OnSuccessListener<DocumentSnapshot> {
     private final ObservableEmitter<DocumentSnapshot> emitter;
     private final boolean last;

     public Callback(boolean lastvalue, ObservableEmitter<DocumentSnapshot> e) {
        this.last = lastvalue;
        this.emitter = e;
     }

     @Override
     public void onSuccess(DocumentSnapshot value) {
         emitter.onNext(value);
         if (last) {
             emitter.onComplete();
         }
     }
}


Observable<DocumentSnapshot> observable = Observable.create(new ObservableOnSubscribe<DocumentSnapshot>() {
        @Override
        public void subscribe(ObservableEmitter<DocumentSnapshot> e) throws Exception {
            int i = 1;
            for (Result result : resultList) {
                /* callback object now knows which is the last request so it can emit the onComplete */
                Callback callbackInstance = new Callback(resultList.size() == i, e);
                i++;
                FirebaseFirestore.getInstance().collection(COLLECTION_NAME)
                            .document(result.getId()).get().addOnSuccessListener(callbackInstance);
                }
            }
        });

然后，当订阅者的onComplete动作被点击时，对Firebase的所有请求都应完成。

RxJava2：对列表中的每个项目执行异步功能，然后等待回调

1 个答案: