RXJava.确定 for 循环中的所有 obervable 何时完成 [英] RXJava. Identify when all obervables inside for loop are finished

问题描述

我想执行以下操作.我有一个交易列表，我想通过为每个交易发出 2 个 api 请求(我正在使用 Retrofit2)来更新这些交易，然后将结果保存到数据库中(使用观察者).经过一番搜索，我决定使用 zip 运算符来组合 2 个请求，但我遇到的问题是我无法确定整个过程何时完成以更新 UI.代码看起来像这样.

I want to perform the following. I have a list of transactions which i want to update by making 2 api requests (i am using retrofit2), for each transactions and then saving the result into a database(using the observer). After some searching i decided to use zip operator to combine the 2 requests but the issue that i'm have is that i cannot identify when the whole process is finished to update the UI. Code looks like this.

for (Transaction realmTransaction : allTransactions) {

        Observable<Map<String, String>> obs1 = getObs1(realmTransaction);

        Observable<Map<String, String>> obs2= getObs2(realmTransaction);

       Observable.zip(obs1, obs2,
                (map1, map2) -> {
                    Map<String, String> combined = new HashMap<>();
// do some processing and return a single map after 
                    return combined;
                })
                .subscribeOn(Schedulers.io())
                .observeOn(Schedulers.computation())
                .observeOn(AndroidSchedulers.mainThread())
                .subscribe(getObserver(realmTransaction));
    }

public Observer<Map<String, String>> getObserver(Transaction t){
return new Observer<Map<String, String>>() {
                    @Override
                    public void onSubscribe(Disposable d) {

                    }

                    @Override
                    public void onNext(Map<String, String> stringStringMap) {
// update database
                    }

                    @Override
                    public void onError(Throwable e) {

                    }

                    @Override
                    public void onComplete() {

                    }
                }
}

我拥有的观察者更新了 realmTransaction 对象的一个​​字段.

The observer that i have updates a field of the realmTransaction object.

我的问题是如何在 for 循环结束时收到通知?

我想在整个过程完成后发送一个事件(可能使用 EventBust)以启动其他方法.

I would like to sent an event (maybe use EventBust) after the whole process has finish to kick off some other method.

谢谢

我还有一个小问题是关于我在 zip 运算符中提供的函数，我如何指定该函数将在哪个线程上运行?我想为此使用计算线程，这就是为什么我将observeOn 两次，但我在任何地方都找不到答案

Also another small question that i have is about the function that i provide inside the zip operator, how can i specify on which thread that function will run on? I would like to use a computation thread for that thats why i put observeOn twice, but I couldnt find an answer anywhere

推荐答案

每当你有 for 循环时，你应该考虑 range、fromArray 或 fromIterable.此外，您可能不需要完整的 subscribe 而是 doOnNext():

Whenever you have a for loop, you should think about range, fromArray or fromIterable. In addition, you may not need the full subscribe but doOnNext():

Observable.fromIterable(allTransactions)
    .flatMap(realmTransaction -> {
        Observable<Map<String, String>> obs1 = getObs1(realmTransaction);

        Observable<Map<String, String>> obs2= getObs2(realmTransaction);

        return Observable.zip(obs1, obs2, (map1, map2) -> {
            Map<String, String> combined = new HashMap<>();
            // do some processing and return a single map after 
            return combined;
        })
        .subscribeOn(Schedulers.io())
        .observeOn(AndroidSchedulers.mainThread())
        .doOnNext(stringStringMap -> handle(stringStringMap, realmTransaction));
   })
   .ignoreElements()
   .subscribe(() -> handleCompleted(), e -> handleError(e));

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