Android rxJava 错误处理与改造

Question

我正在使用较新的 RX java 而不是

Observable.create(new Observable.OnSubscribeFunc<T>() {...});

这是使用的：（由于弃用）

Observable.create(new Observable.OnSubscribe<T>() {...});

（这可能很重要，因为大多数示例、教程、探索都使用旧的...）

好吧，让我们看看我的问题。我有一个 Java 类，其中的相关部分：

private interface ApiManagerService {

    @FormUrlEncoded
    @POST("/login")
    User getUser(@Field("username") String userName, @Field("password") String password);

}


private static RestAdapter restAdapter = new RestAdapter.Builder()
    .setEndpoint(HOST)
    .setLogLevel(RestAdapter.LogLevel.FULL)
    .build();

private static ApiManagerService apiManager = restAdapter.create(ApiManagerService.class);

public static Subscription login(final String userName, final String password, Observer<User> observer) {
    return Observable.create(new Observable.OnSubscribe<User>() {
        @Override
        public void call(Subscriber<? super User> subscriber) {
            try {

                User user = apiManager.getUser(userName, password);

                subscriber.onNext(user);
                subscriber.onCompleted();

            } catch (RetrofitError e) {
                subscriber.onError(e);
            } catch (Throwable e) {
                subscriber.onError(e);
            }
        }
    }

    ).subscribeOn(Schedulers.io())
     .retry(3)
     .observeOn(AndroidSchedulers.mainThread())
     .subscribe(observer);
}

如果一切正常，这段代码几乎可以完美运行。但是如果我犯了一个故意的错误，比如我关闭了 WiFi .. 而不是改造得到 "UnKnownHostException"... 因为它应该发生在改造调用 (getUser) 中try catch 块。但不是将错误处理到 onError(Throwable t) --> 我可以处理的地方，它只是使应用程序崩溃。所以这就像错误永远不会到达 catch 块一样。奇怪的是，HTTP 错误（如 404、401 等）被捕获，由 onError(...) 得到，一切都很好。

从 .retry(3) 开始，一切都在崩溃前进行了 3 次，但没有一次进入 catch 子句。

编辑 1

LogCat 输出：

    01-08 16:19:31.576  15285-16162/asd.bdef.gh D/Retrofit﹕ ---- ERROR https://testapi.com/api/login
    01-08 16:19:31.606  15285-16162/asd.bdef.gh D/Retrofit﹕ java.net.UnknownHostException: Unable to resolve host "testapi.com": No address associated with hostname
                at java.net.InetAddress.lookupHostByName(InetAddress.java:394)
                at java.net.InetAddress.getAllByNameImpl(InetAddress.java:236)
                at java.net.InetAddress.getAllByName(InetAddress.java:214)
                at com.squareup.okhttp.internal.Network.resolveInetAddresses(Network.java:29)
                at com.squareup.okhttp.internal.http.RouteSelector.resetNextInetSocketAddress(RouteSelector.java:259)
                at com.squareup.okhttp.internal.http.RouteSelector.nextProxy(RouteSelector.java:233)
                at com.squareup.okhttp.internal.http.RouteSelector.nextUnconnected(RouteSelector.java:159)
                at com.squareup.okhttp.internal.http.RouteSelector.next(RouteSelector.java:133)
                at com.squareup.okhttp.internal.http.HttpEngine.connect(HttpEngine.java:314)
                at com.squareup.okhttp.internal.http.HttpEngine.sendRequest(HttpEngine.java:237)
                at com.squareup.okhttp.internal.huc.HttpURLConnectionImpl.execute(HttpURLConnectionImpl.java:423)
                at com.squareup.okhttp.internal.huc.HttpURLConnectionImpl.connect(HttpURLConnectionImpl.java:105)
                at com.squareup.okhttp.internal.huc.HttpURLConnectionImpl.getOutputStream(HttpURLConnectionImpl.java:239)
                at com.squareup.okhttp.internal.huc.DelegatingHttpsURLConnection.getOutputStream(DelegatingHttpsURLConnection.java:218)
                at com.squareup.okhttp.internal.huc.HttpsURLConnectionImpl.getOutputStream(HttpsURLConnectionImpl.java:25)
                at retrofit.client.UrlConnectionClient.prepareRequest(UrlConnectionClient.java:68)
                at retrofit.client.UrlConnectionClient.execute(UrlConnectionClient.java:37)
                at retrofit.RestAdapter$RestHandler.invokeRequest(RestAdapter.java:321)
                at retrofit.RestAdapter$RestHandler.access0(RestAdapter.java:220)
                at retrofit.RestAdapter$RestHandler.invoke(RestAdapter.java:265)
                at retrofit.RxSupport.run(RxSupport.java:55)
                at java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:390)
                at java.util.concurrent.FutureTask.run(FutureTask.java:234)
                at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1080)
                at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:573)
                at retrofit.Platform$Android.run(Platform.java:142)
                at java.lang.Thread.run(Thread.java:841)
    01-08 16:19:31.606  15285-16162/asd.bdef.gh D/Retrofit﹕ ---- END ERROR
    01-08 16:19:31.977  15285-15285/asd.bdef.gh D/AndroidRuntime﹕ Shutting down VM
    01-08 16:19:31.977  15285-15285/asd.bdef.gh W/dalvikvm﹕ threadid=1: thread exiting with uncaught exception (group=0x41c9d8b0)
    01-08 16:19:31.977  15285-15285/asd.bdef.gh E/AndroidRuntime﹕ FATAL EXCEPTION: main

给定的api地址不是真实地址，但真实地址是可达的。我刚刚关闭了 WiFi 以测试错误处理。

还有一个用例：如果我添加到 observable .onExceptionResumeNext([2nd observable]) 而不是它转到第二个 observable，它不会崩溃。但这不是解决问题的方法。

编辑 2

ApiManager.login(userName, pass, new Observer<User>() {
    @Override
    public void onCompleted() { }

    @Override
    public void onError(Throwable e) {
        DialogManager.showBasicErrorDialog(getApplicationContext(), e.getLocalizedMessage());
        logger.showLog("Login Not ok");
        e.printStackTrace();
    }

    @Override
    public void onNext(User user) {
        logger.showLog("login ok, user: " + user.getName().toString());
        {...}
    }

});

编辑 3

FATAL EXCEPTION: main
rx.exceptions.OnErrorFailedException: Error occurred when trying to propagate error to Observer.onError
        at rx.observers.SafeSubscriber._onError(SafeSubscriber.java:175)
        at rx.observers.SafeSubscriber.onError(SafeSubscriber.java:97)
        at rx.internal.operators.NotificationLite.accept(NotificationLite.java:144)

{...}

Caused by: java.lang.NullPointerException: Attempt to read from field 'rx.functions.Action0 rx.schedulers.TrampolineScheduler$TimedAction.action' on a null object reference
        at rx.schedulers.TrampolineScheduler$InnerCurrentThreadScheduler.enqueue(TrampolineScheduler.java:85)

在此先感谢您的帮助。

Answer 1

你不必使用 Retrofit 构建自己的 Observable，因为 Retrofit 可以直接 return Observable:

http://square.github.io/retrofit/

Retrofit also integrates RxJava to support methods with a return type of rx.Observable

@GET("/user/{id}/photo") Observable getUserPhoto(@Path("id") int id);

（您不必自己处理错误）

你能post你崩溃的堆栈跟踪吗？正如我和您的想法一样，您的应用程序不应该崩溃。

Answer 2

看起来你可能运行一个问题已经在 RxJava 1.0 中得到修复：

TrampolineScheduler NullPointerException

Android rxJava 错误处理与改造

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