我在设备上获得已安装应用的列表。这是一项代价高昂的操作，因此我使用Rx：
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));
然而，我的问题是处理错误。 通常，用户启动此屏幕，等待加载应用程序，选择最佳选择并转到下一页。但是，当用户快速更改UI时，应用程序会与NullPointer崩溃。
好的，所以我实现了这个onError。但是它仍然无法正常工作，并且在上面的用例中它会让我失望：
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)
我该如何正确处理这个问题？
答案 0 :(得分：14)
.doOnError()是一个运营商，并不是Subscriber的一部分。
因此，拥有.doOnError()并不算作已实施的onError()。
关于其中一条评论中的问题，当然可以使用lambdas。
在这种情况下，只需替换
.doOnError(throwable -> L.e(TAG, "Throwable " + throwable.getMessage()))
.subscribe(s -> createListView(s, view))
与
.subscribe(s -> createListView(s, view),
throwable -> L.e(TAG, "Throwable " + throwable.getMessage()))
答案 1 :(得分：12)
我的看法是：你可能正在使用
中的Action1.subscribe(s -> createListView(s, view));
您需要将其替换为具有抽象方法onError的Subscriber或Observer。此方法将从subscriber.onError(new Throwable());
EDIT:我就是这样做的。仔细观察后，我认为代码中的主要问题是即使没有错误也会调用subscriber.onError的早期部分。您可能不需要map因为您在技术上按原样传递数据而无需操作。但我留下它以防以后需要它。
Observable.create(new Observable.OnSubscribe<Application>() {
@Override
public void call(Subscriber<? super Application> subscriber) {
List result = getUserApps();
if (result != null){
for (Application app : result){
subscriber.onNext(app);
}
subscriber.onComplete();
}else{
subscriber.onError(new IOException("no permission / no internet / etc"));
//or if this is a try catch event you can pass the exception
}
}
})
.subscribeOn(Schedulers.io())//the thread *observer* runs in
.observeOn(AndroidSchedulers.mainThread())//the thread *subscriber* runs in
.map(new Func1<Application, String>() {
// Mapping methods are where data are manipulated.
// You can simply skip this and
//do the same thing in Subscriber implementation
@Override
public String call(Application application) {
return application.getName();
}
}).subscribe(new Subscriber<String>() {
@Override
public void onCompleted() {
Toast.makeText(context, "completed", Toast.LENGTH_SHORT).show();
//because subscriber runs in main UI thread it's ok to do UI stuff
//raise Toast, play sound, etc
}
@Override
public void onError(Throwable e) {
Log.e("getAppsError", e.getMessage());
//raise Toast, play sound, etc
}
@Override
public void onNext(String s) {
listAdapter.add(s);
}
});
答案 2 :(得分：5)
以下是新手回复（因为我是javarx的新手，最后解决了这个问题）：
以下是您的实施：
Observable.create(new Observable.OnSubscribe<RegionItem>() {
@Override
public void call(Subscriber<? super RegionItem> subscriber) {
subscriber.onError(new Exception("TADA !"));
}
})
.doOnNext(actionNext)
.doOnError(actionError)
.doOnCompleted(actionCompleted)
.subscribe();
在之前的实现中，当我订阅时，我触发了错误流程......我得到了一个应用程序崩溃。
问题是您必须从subscribe（）调用中管理错误。 “doOnError（...）”只是一种帮助，可以克隆错误并为您提供一个新的位置，以便在发生错误后执行某些操作。但它没有处理错误。
所以你必须改变你的代码：
Observable.create(new Observable.OnSubscribe<RegionItem>() {
@Override
public void call(Subscriber<? super RegionItem> subscriber) {
subscriber.onError(new Exception("TADA !"));
}
})
.subscribe(actionNext, actionError, actionCompleted);
不确定真正的解释，但这就是我解决它的方法。希望它会有所帮助。