Kotlin Can'；t在dispose（）之后使用相同的DisposableObserver和subscribeWith两次

代码（Kotlin）非常简单，但我不明白，为什么不能再次使用相同的对象订阅

val x = Observable.interval(1L, TimeUnit.SECONDS, Schedulers.io())
    .map {
        println("emitting=$it")
        it.toString()
    }.publish().autoConnect()

val o = object : DisposableObserver<String>() {
    override fun onComplete() {}
    override fun onNext(t: String) = println("O:=$t")
    override fun onError(e: Throwable) {}
}
println("---------- subscribe ----------")
val s2 = x.subscribeWith(o)

sleepSeconds(2)
println("---------- dispose ----------")
s2.dispose()

sleepSeconds(2)
println("---------- subscribe again ----------")
x.subscribeWith(o) //<<-- This doesn't work!!!!

sleepSeconds(5)

---

当我创建类DisposableObserver的新实例时，它工作得很好

DisposableObserver

设计为只能订阅一次。当您在DisposableObserver的引擎盖下查看时，您将看到AtomicReference

上游

，它在observer订阅时保存了当前的DisposableObserver

public abstract class DisposableObserver<T> implements Observer<T>, Disposable {

    final AtomicReference<Disposable> upstream = new AtomicReference<Disposable>();

    @Override
    public final void onSubscribe(@NonNull Disposable d) {
        if (EndConsumerHelper.setOnce(this.upstream, d, getClass())) {
            onStart();
        }
    }
// rest of code

这就是为什么您不能使用相同的DisposableObserver实例重新订阅，但可以使用新实例

public abstract class DisposableObserver<T> implements Observer<T>, Disposable {

    final AtomicReference<Disposable> upstream = new AtomicReference<Disposable>();

    @Override
    public final void onSubscribe(@NonNull Disposable d) {
        if (EndConsumerHelper.setOnce(this.upstream, d, getClass())) {
            onStart();
        }
    }
// rest of code

public static boolean setOnce(AtomicReference<Disposable> upstream, Disposable next, Class<?> observer) {
        ObjectHelper.requireNonNull(next, "next is null");
        if (!upstream.compareAndSet(null, next)) { 
            next.dispose();  // dispose next if there is set upstream previously 
            if (upstream.get() != DisposableHelper.DISPOSED) {
                reportDoubleSubscription(observer);
            }
            return false;
        }
        return true;  
    }