RxJava：CountDownLatch 永不停止

Question

最近在学习RxJava。我们都知道CountDownLatch数到zero就会停止。好吧，但是当我在下面运行代码时， CountDownLaych 永远不会停止！我尝试运行与 Java 项目相同的代码，可以停止！

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);

    final CountDownLatch latch = new CountDownLatch(5);
    Observable
            .interval(1, TimeUnit.SECONDS)
            .subscribe(new Action1<Long>() {
                @Override
                public void call(Long counter) {
                    latch.countDown();
                    long count = latch.getCount();
                    Log.d(TAG, "call get -> " + counter + ", latch count -> " + count);
                }
            });

    try {
        latch.await();
    } catch (InterruptedException e) {
        e.printStackTrace();
    }
}

在 Android Studio 中，这些代码将输出如下：

D/MainActivity: call get -> 0, latch count -> 4
D/MainActivity: call get -> 1, latch count -> 3
D/MainActivity: call get -> 2, latch count -> 2
D/MainActivity: call get -> 3, latch count -> 1
D/MainActivity: call get -> 4, latch count -> 0
D/MainActivity: call get -> 5, latch count -> 0
D/MainActivity: call get -> 6, latch count -> 0
D/MainActivity: call get -> 7, latch count -> 0
....

Answer 1

根据 the documentation，锁存器不会在零时停止计数。相反：

If the current count equals zero then nothing happens.

尝试将您的 try 块修改为如下所示：

Log.d(TAG, "call await");
latch.await();
Log.d(TAG, "released");

我相信你会看到当你的闩锁达到零时线程被释放。如果您希望您的 Observable 在这种情况发生时停止发射，那么您将不得不取消订阅它。

RxJava：CountDownLatch 永不停止

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