如何正确处理RxJava(Android)内部的onError? [英] How to properly handle onError inside RxJava (Android)?
问题描述
我正在获取设备上已安装应用程序的列表.这是一项昂贵的操作，所以我为此使用了Rx:
I'm getting a list of installed apps on the device. It's a costly operation, so I'm using Rx for that:
Observable<List> observable = Observable.create(subscriber -> {
List result = getUserApps();
subscriber.onNext(result);
subscriber.onError(new Throwable());
subscriber.onCompleted();
});
observable
.map(s -> {
ArrayList<String> list = new ArrayList<>();
ArrayList<Application> applist = new ArrayList<>();
for (Application p : (ArrayList<Application>) s) {
list.add(p.getAppName());
applist.add(p);
}
return applist;
})
.subscribeOn(Schedulers.newThread())
.observeOn(AndroidSchedulers.mainThread())
.doOnError(throwable -> L.e(TAG, "Throwable " + throwable.getMessage()))
.subscribe(s -> createListView(s, view));
但是，我的问题是处理错误.通常，用户启动此屏幕，等待应用程序加载，选择最佳应用程序并转到下一页.但是，当用户快速更改UI时-NullPointer导致应用程序崩溃.
However, my problem is with handling errors. Normally, user launches this screen, waits for apps to load, selects what is best and goes to next page. However, when user quickly changes the UI - app crashes with NullPointer.
好的，所以我实现了这个 onError .但是它仍然不起作用，在上述用例中，它引发了我这个问题:
Okay, so I implemented this onError. However it still doesn't work, and with above usecase it throws me this:
04-15 18:12:42.530 22388-22388/pl.digitalvirgo.safemob E/AndroidRuntime﹕ FATAL EXCEPTION: main
java.lang.IllegalStateException: Exception thrown on Scheduler.Worker thread. Add `onError` handling.
at rx.internal.schedulers.ScheduledAction.run(ScheduledAction.java:52)
at android.os.Handler.handleCallback(Handler.java:730)
at android.os.Handler.dispatchMessage(Handler.java:92)
at android.os.Looper.loop(Looper.java:176)
at android.app.ActivityThread.main(ActivityThread.java:5419)
at java.lang.reflect.Method.invokeNative(Native Method)
at java.lang.reflect.Method.invoke(Method.java:525)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1046)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:862)
at dalvik.system.NativeStart.main(Native Method)
Caused by: rx.exceptions.OnErrorNotImplementedException
at rx.Observable$31.onError(Observable.java:7134)
at rx.observers.SafeSubscriber._onError(SafeSubscriber.java:154)
at rx.observers.SafeSubscriber.onError(SafeSubscriber.java:111)
at rx.internal.operators.OperatorDoOnEach$1.onError(OperatorDoOnEach.java:70)
at rx.internal.operators.NotificationLite.accept(NotificationLite.java:147)
at rx.internal.operators.OperatorObserveOn$ObserveOnSubscriber.pollQueue(OperatorObserveOn.java:177)
at rx.internal.operators.OperatorObserveOn$ObserveOnSubscriber.access$000(OperatorObserveOn.java:65)
at rx.internal.operators.OperatorObserveOn$ObserveOnSubscriber$2.call(OperatorObserveOn.java:153)
at rx.internal.schedulers.ScheduledAction.run(ScheduledAction.java:47)
at android.os.Handler.handleCallback(Handler.java:730)
at android.os.Handler.dispatchMessage(Handler.java:92)
at android.os.Looper.loop(Looper.java:176)
at android.app.ActivityThread.main(ActivityThread.java:5419)
at java.lang.reflect.Method.invokeNative(Native Method)
at java.lang.reflect.Method.invoke(Method.java:525)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1046)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:862)
at dalvik.system.NativeStart.main(Native Method)
Caused by: java.lang.Throwable
at pl.digitalvirgo.safemob.fragments.wizard.ApplicationsFragment.lambda$getAppList$25(ApplicationsFragment.java:267)
at pl.digitalvirgo.safemob.fragments.wizard.ApplicationsFragment.access$lambda$2(ApplicationsFragment.java)
at pl.digitalvirgo.safemob.fragments.wizard.ApplicationsFragment$$Lambda$3.call(Unknown Source)
at rx.Observable$1.call(Observable.java:145)
at rx.Observable$1.call(Observable.java:137)
at rx.Observable.unsafeSubscribe(Observable.java:7304)
at rx.internal.operators.OperatorSubscribeOn$1$1.call(OperatorSubscribeOn.java:62)
at rx.internal.schedulers.ScheduledAction.run(ScheduledAction.java:47)
at java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:390)
at java.util.concurrent.FutureTask.run(FutureTask.java:234)
at java.util.concurrent.ScheduledThreadPoolExecutor$ScheduledFutureTask.access$201(ScheduledThreadPoolExecutor.java:153)
at java.util.concurrent.ScheduledThreadPoolExecutor$ScheduledFutureTask.run(ScheduledThreadPoolExecutor.java:267)
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1080)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:573)
at java.lang.Thread.run(Thread.java:841)
我应该如何正确处理此问题?
How should I properly handle this problem?
推荐答案
.doOnError()是运算符，而不是 Subscriber 的一部分.
.doOnError() is an operator, and is not as such a part of the Subscriber.
因此，具有 .doOnError()并不算作已实现的 onError().
Therefore, having a .doOnError() does not count as an implemented onError().
关于其中一条评论中的问题，当然可以使用lambda.
About the question in one of the comments, of course it is possible to use lambdas.
在这种情况下，只需替换
In this case simply replace
.doOnError(throwable -> L.e(TAG, "Throwable " + throwable.getMessage()))
.subscribe(s -> createListView(s, view))
使用
.subscribe(s -> createListView(s, view),
throwable -> L.e(TAG, "Throwable " + throwable.getMessage()))
这篇关于如何正确处理RxJava(Android)内部的onError?的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！
