如何在RxJava2中的自定義Observable中獲得觀察者的處置動作的通知

Question

在此線程中 ，提出了一個有關如何觀察取消訂閱事件的問題，以便您可以在取消訂閱之后清理並刪除該監聽器。 但是，在RxJava2中，上述線程的方法不再起作用。

def myObservable = Observable.create({ aEmitter ->
    val listener = {event -> 
      aEmitter.onNext(event);                
    }
    existingEventSource.addListener(listener)

    // Fails since aEmitter doesn't have an add() method nor does Subscriptions exist.
    aEmitter.add(Subscriptions.create(() -> existingEventSource.removeListener(listener)));
})

在RxJava2中解決此問題的正確方法是什么？

Answer 1

請查看stringObservable Observable，如何處理訂閱。

public class MyTest {
  @Mock private MyService mock;

  @Before
  public void setUp() throws Exception {
    MockitoAnnotations.initMocks(this);
  }

  @Test
  public void nam3e() {
    ArrayList<Listener> listeners = new ArrayList<>();

    doAnswer(
            invocation -> {
              Object[] args = invocation.getArguments();
              Listener arg = (Listener) args[0];

              listeners.add(arg);

              return null;
            })
        .when(mock)
        .addListener(any());

    Observable<String> stringObservable =
        Observable.create(
            e -> {
              Listener listener =
                  s -> {
                    e.onNext(s);
                  };

              mock.addListener(listener);

              e.setCancellable(
                  () -> {
                    mock.removeListener(listener);
                  });
            });

    TestObserver<String> test = stringObservable.test();

    Listener listener = listeners.get(0);
    listener.onNext("Wurst");

    test.assertNotComplete().assertValue("Wurst");
    verify(mock, times(1)).addListener(any());

    test.dispose();

    verify(mock, times(1)).removeListener(any());
  }

  public interface MyService {
    void addListener(Listener listener);

    void removeListener(Listener listener);
  }

  @FunctionalInterface
  public interface Listener {
    void onNext(String s);
  }
}