Rxjava2 doOnComplete

doOnComplete操作符的作用是在调用onComplete后执行。

Observable.create(new ObservableOnSubscribe<String>() {
            @Override
            public void subscribe(@NotNull ObservableEmitter<String> emitter) throws Exception {
                emitter.onNext("1");
                emitter.onComplete();
            }
        }).doOnComplete(new Action() {
            @Override
            public void run() throws Exception {
                System.out.println("doOnComplete");
            }
        }).subscribe(new Observer<String>() {
            @Override
            public void onSubscribe(@NotNull Disposable d) {
                System.out.println("onSubscribe");
                mDisposable = d;
            }

            @Override
            public void onNext(@NotNull String s) {
                System.out.println("onNext " + s);
            }

            @Override
            public void onError(@NotNull Throwable e) {
                System.out.println("onError");
            }

            @Override
            public void onComplete() {
                System.out.println("onComplete");
            }
        });

输出

onSubscribe
onNext 1
doOnComplete
onComplete

看看源码

  public final Observable<T> doOnComplete(Action onComplete) {
        return doOnEach(Functions.emptyConsumer(), Functions.emptyConsumer(), onComplete, Functions.EMPTY_ACTION);
    }
    
  private Observable<T> doOnEach(Consumer<? super T> onNext, Consumer<? super Throwable> onError, Action onComplete, Action onAfterTerminate) {
        ...
        return RxJavaPlugins.onAssembly(new ObservableDoOnEach<T>(this, onNext, onError, onComplete, onAfterTerminate));
    }  

当我们调用onComplete时， onComplete.run();就会执行，并且是在下游收到onComplete事件之前调用。

public void onComplete() {
            ...
            try {
                onComplete.run();
            } catch (Throwable e) {
                Exceptions.throwIfFatal(e);
                onError(e);
                return;
            }

            done = true;
            downstream.onComplete();

           ...
        }