如何在RxJava2中等待可能的项目列表完成？

Question

如果我对如何使用RxJava2缺乏基本的了解，请提前道歉，因为在我看来，这应该是非常基本的东西。我已经因为不成功的Google搜索而绞尽脑汁，所以欢迎任何资源推荐。为了清晰起见，我选择使用解决方法代码的“净化”表示。

我有一个RxJava2函数asyncCallForList（），它返回一个也许

每个项目所需的完整数据位于另一个数据库位置，使用另一个函数asyncCallForItem（uid）检索，该函数返回一个

所需的功能是在填充列表中的所有对象后更新我的UI。

在附加到初始的doOn成功（）中循环遍历生成的数组列表很容易

这得到了期望的结果，但感觉是错误的做法——我怀疑有一种更优雅的RxJava2解决方案。基本上，我创建了一个自定义的可观察的，在其中循环列表中的项目，并获得每个项目的完整数据。但是，我不是每次填充CustomClass项时都更新UI，而是增加计数器，然后检查计数器是否超过或等于初始列表大小。当这个条件满足时，我调用可观察发射器的onComplete（）方法，并在那里更新UI。

private void fetchRemoteDataAndUpdateUi() {

    //Counter reset to zero before any asynchronous calls are made.
    int count = 0;

    Maybe<ArrayList<CustomClass>> itemList = asyncCallForList();
    Consumer<ArrayList<CustomClass>> onListReturnedSuccess;

    onListReturnedSuccess = new Consumer<ArrayList<CustomClass >>() {
        @Override
        public void accept(ArrayList<CustomClass> list) throws Exception {
            //Custom observable created here, in which the resulting array list is processed.
            listObservable = Observable.create(new ObservableOnSubscribe<CustomClass>() {
                @Override
                public void subscribe(final ObservableEmitter<CustomClass> e) throws Exception {
                    for (CustomClass customClass : list) {
                        final CustomClass thisCustomClass = customClass;
                        //Call to get full data on list item called here.
                        asyncCallForItem(customClass.getUid())
                                .doOnSuccess(new Consumer<CustomClass>() {
                                    @Override
                                    public void accept(CustomClass customClass) throws Exception {
                                        thisCustomClass.update(customClass);
                                        e.onNext(thisCustomClass);
                                        count++;
                                        if (count >= list.size()) {
                                            e.onComplete();
                                        }
                                    }
                                }).subscribe();
                    }
                }
            });

            listObservable
                    .observeOn(AndroidSchedulers.mainThread())
                    .subscribeOn(Schedulers.io())
                    .subscribe(new Observer<CustomClass>() {
                        @Override
                        public void onSubscribe(Disposable d) {
                        }

                        @Override
                        public void onNext(CustomClass customClass) {
                            //Here I add the populated CustomClass object to an ArrayList field that is utilised by the UI.
                            listForUi.add(customClass);
                        }

                        @Override
                        public void onError(Throwable e) {

                        }

                        @Override
                        public void onComplete() {
                            //Here the UI is finally updated once all CustomClass objects have been populated.
                            updateUi();
                        }
                    });
        }
    };


    //Kick everything off.
    itemList.doOnSuccess(onListReturnedSuccess).subscribe();
}




Answer 1

flatMapit！

asyncCallForList()
.subscribeOn(Schedulers.io())
.flatMapSingle(list ->
    Flowable.fromIterable(list)
    .flatMapMaybe(item -> 
        asyncCallForItem(item.id)
        .subscribeOn(Schedulers.io())
        .doOnSuccess(response -> {
            // copy state from the original item
            response.text = item.text;
        })
    , 1) // number of concurrent item calls
    .toList()
)
.observeOn(AndroidSchedulers.mainThread())
.subscribe(successList -> { /* update UI */ }, error -> { /* report error */ });