RxJava：observeOn、subscribeOn 和 doFinally，在 IO 和 UI 线程之间切换

Question

我运行遇到一个问题，我的可观察对象在 IO 线程上订阅并在 android 主（UI）线程上观察，但 doFinally运算符在 IO 线程上是运行，它需要在 UI 线程上是运行。

用例与这个medium article几乎完全一样。

我基本上想在 Observable 被订阅时显示 ProgressBar 并在 Observable 终止或完成时隐藏 ProgressBar。

我收到的错误是：java.lang.IllegalStateException: 当前线程必须有循环程序！

任何人都可以帮我将 doFinally 操作移回具有循环程序的 UI 线程吗？还是我遗漏了一些其他信息？

编辑用例工作流程是：

-> 启动 Activity

-> 初始化

-> 执行可观察流

-> 开始新的 Activity 并完成当前的 activity

-> 新 activity

-> 开始原始 activity 并完成

-> 重复初始化

非常感谢。

详情：

RxJava 2.0.7
RxAndroid 2.0.1
Android sdk 最小 14 和目标 25

示例代码

listUseCase.execute(null)
            .doOnSubscribe(new Consumer<Disposable>() {
                @Override
                public void accept(@NonNull Disposable disposable) throws Exception {
                    getView().showLoading(true);
                }
            })
            .doFinally(new Action() {
                @Override
                public void run() throws Exception {
                    getView().showLoading(false);
                }
            })
            .subscribeOn(schedulerProvider.io())
            .observeOn(schedulerProvider.main())
            .subscribe(
                    new Consumer<List<AccountEntity>>() {
                        @Override
                        public void accept(@NonNull List<AccountEntity> accountEntities) throws Exception {
                            getView().setAccounts(accountEntities);
                        }
                    },
                    new Consumer<Throwable>() {
                        @Override
                        public void accept(@NonNull Throwable throwable) throws Exception {
                            if (isViewAttached()) {
                                getView().showError(throwable.getMessage());
                            }
                        }
                    }
            );

堆栈跟踪：

FATAL EXCEPTION: RxCachedThreadScheduler-1
  Process: com.example.android.demo.customerfirst.alpha, PID: 16685
  java.lang.IllegalStateException: The current thread must have a looper!
      at android.view.Choreographer.initialValue(Choreographer.java:96)
      at android.view.Choreographer.initialValue(Choreographer.java:91)
      at java.lang.ThreadLocal$Values.getAfterMiss(ThreadLocal.java:430)
      at java.lang.ThreadLocal.get(ThreadLocal.java:65)
      at android.view.Choreographer.getInstance(Choreographer.java:192)
      at android.animation.ValueAnimator$AnimationHandler.<init>(ValueAnimator.java:600)
      at android.animation.ValueAnimator$AnimationHandler.<init>(ValueAnimator.java:575)
      at android.animation.ValueAnimator.getOrCreateAnimationHandler(ValueAnimator.java:1366)
      at android.animation.ValueAnimator.end(ValueAnimator.java:998)
      at android.graphics.drawable.AnimatedVectorDrawable.stop(AnimatedVectorDrawable.java:439)
      at android.widget.ProgressBar.stopAnimation(ProgressBar.java:1523)
      at android.widget.ProgressBar.onVisibilityChanged(ProgressBar.java:1583)
      at android.view.View.dispatchVisibilityChanged(View.java:8643)
      at android.view.View.setFlags(View.java:9686)
      at android.view.View.setVisibility(View.java:6663)
      at android.widget.ProgressBar.setVisibility(ProgressBar.java:1563)
      at com.example.android.demo.customerfirst.featuresstore.list.ProductListActivity.showLoading(ProductListActivity.java:121)
      at com.example.android.demo.customerfirst.featuresstore.list.ProductListPresenterMediator.run(ProductListPresenterMediator.java:56)
      at io.reactivex.internal.operators.observable.ObservableDoFinally$DoFinallyObserver.runFinally(ObservableDoFinally.java:144)
      at io.reactivex.internal.operators.observable.ObservableDoFinally$DoFinallyObserver.onComplete(ObservableDoFinally.java:94)
      at io.reactivex.internal.observers.DisposableLambdaObserver.onComplete(DisposableLambdaObserver.java:73)
      at io.reactivex.internal.observers.DeferredScalarDisposable.complete(DeferredScalarDisposable.java:84)
      at io.reactivex.internal.operators.observable.ObservableFromCallable.subscribeActual(ObservableFromCallable.java:52)
      at io.reactivex.Observable.subscribe(Observable.java:10700)
      at io.reactivex.internal.operators.observable.ObservableDoOnLifecycle.subscribeActual(ObservableDoOnLifecycle.java:33)
      at io.reactivex.Observable.subscribe(Observable.java:10700)
      at io.reactivex.internal.operators.observable.ObservableDoFinally.subscribeActual(ObservableDoFinally.java:45)
      at io.reactivex.Observable.subscribe(Observable.java:10700)
      at io.reactivex.internal.operators.observable.ObservableSubscribeOn.run(ObservableSubscribeOn.java:39)
      at io.reactivex.Scheduler.run(Scheduler.java:138)
      at io.reactivex.internal.schedulers.ScheduledRunnable.run(ScheduledRunnable.java:59)
      at io.reactivex.internal.schedulers.ScheduledRunnable.call(ScheduledRunnable.java:51)
      at java.util.concurrent.FutureTask.run(FutureTask.java:237)
      at java.util.concurrent.ScheduledThreadPoolExecutor$ScheduledFutureTask.access1(ScheduledThreadPoolExecutor.java:152)
      at java.util.concurrent.ScheduledThreadPoolExecutor$ScheduledFutureTask.run(ScheduledThreadPoolExecutor.java:265)
      at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1112)
      at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:587)
      at java.lang.Thread.run(Thread.java:818)

Answer 1

您需要做的就是将 observeOn 移到链上。 observeOn 方法更改调用 onNext、onError 和 onCompleted 的线程，这是内部操作和副作用的工作方式（通过 lift）

listUseCase.execute(null)
            .subscribeOn(schedulerProvider.io()) // Move subscribe on here
            .observeOn(schedulerProvider.main()) // Change threads here
            .doOnSubscribe(new Consumer<Disposable>() {
                @Override
                public void accept(@NonNull Disposable disposable) throws Exception {
                    getView().showLoading(true); // This should be on the main thread also
                }
            })
            .doFinally(new Action() {
                @Override
                public void run() throws Exception {
                    getView().showLoading(false);
                }
            })

            .subscribe(
                    new Consumer<List<AccountEntity>>() {
                        @Override
                        public void accept(@NonNull List<AccountEntity> accountEntities) throws Exception {
                            getView().setAccounts(accountEntities);
                        }
                    },
                    new Consumer<Throwable>() {
                        @Override
                        public void accept(@NonNull Throwable throwable) throws Exception {
                            if (isViewAttached()) {
                                getView().showError(throwable.getMessage());
                            }
                        }
                    }
            );

Answer 2

出现此问题是因为在 activity 为 finished/destroyed 时我没有处理订阅。

现在每个 activity/view 都会告诉演示者它们何时停止或销毁，并且演示者会处理订阅。

这似乎解决了我的问题。

 @Override
public void initialize() {
    if (!isViewAttached()) {
        throw new ViewNotAttachedException();
    }
    disposable = listUseCase.execute(null)
            .subscribeOn(schedulerProvider.io()) // Move subscribe on here
            .observeOn(schedulerProvider.main()) // Change threads here
            .doOnSubscribe(new Consumer<Disposable>() {
                @Override
                public void accept(@NonNull Disposable disposable) throws Exception {
                    getView().showLoading(true); // This should be on the main thread also
                }
            })
            .doFinally(new Action() {
                @Override
                public void run() throws Exception {
                    getView().showLoading(false);
                }
            })
            .subscribe(
                    new Consumer<List<AccountEntity>>() {
                        @Override
                        public void accept(@NonNull List<AccountEntity> accountEntities) throws Exception {
                            getView().setAccounts(accountEntities);
                        }
                    },
                    new Consumer<Throwable>() {
                        @Override
                        public void accept(@NonNull Throwable throwable) throws Exception {
                            if (isViewAttached()) {
                                getView().showError(throwable.getMessage());
                            }
                        }
                    }
            );
}

@Override
public void dispose() {
    if (disposable != null) {
        disposable.dispose();
    }
}

Answer 3

也许为时已晚。但是请查看有关 doFinally 的文档 here 他们明确地说“

Calls the specified action after this Observable signals onError or onCompleted or gets disposed by the downstream.

这意味着 doFinally 它无论如何都会被调用，并且不保证你有一个有效的上下文。

我不使用 doFinally 这个东西。我总是设置 loading(false) onNext 或 onError。不漂亮但有效。

RxJava：observeOn、subscribeOn 和 doFinally，在 IO 和 UI 线程之间切换

RxJava: observeOn, subscribeOn, and doFinally, switching between IO and UI thread

java

android

rx-java2