RxJava：如何表达doOnFirst（）？

问题描述

我正在使用RxJava，我有一个 Observable ，里面有多个项目。我想要做的是在第一项上运行函数A，在所有这些项上运行函数B，在 Observable 完成时运行函数C：

I am using RxJava and I have an Observable with multiple items inside. What I would like to do is run function A on the first item, function B on all of them and function C when the Observable is completed:

-----1-----2-----3-----|-->
     |     |     |     |
     run A |     |     |
     |     |     |     |
     run B run B run B |
                       |
                       run C

有一种聪明的方式用lambda函数表达这个吗？我已经有了以下解决方案，但它看起来很难看，我怀疑有更好的方法可以做到这一点：

is there a clever way of expressing this with lambda functions? I have the following solution already, but it looks ugly and I suspect that there is a better way to do this:

observable.subscribe(
        new Action1<Item>() {
            boolean first = true;

            @Override
            public void call(Item item) {
                if (first) {
                    runA(item);
                    first = false;
                }
                runB(fax1);
            }
        },
        throwable -> {},
        () -> runC());

推荐答案

我想我找到了一个简单的解决方案我自己：

I guess I've found an easy solution for this myself:

Observable<Integer> observable = Observable.just(1, 2, 3).share();
observable.take(1).subscribe(this::runA);
observable.subscribe(
    this::runB,
    throwable -> {},
    this::runC);

这是单线程的，它似乎也可以工作多线程，但我不得不承认我到目前为止，我对此并不太自信。

This works single-threaded and it seems to work multi-threaded too, but I have to admit I'm not too confident about that so far.

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