使用 Retrofit 2 和 RxJava 的 concatMap() 中的 NetworkOnMainThreadException

Question

在我的应用程序中，我尝试使用 RxJava 在用户搜索新电影并从网络服务检索电影数据时做出反应。为了做到这一点，我想使用 concatMap 将获取新电影查询的操作连接到向网络服务请求电影。这样做我得到一个 NetworkOnMainThread 异常，我不明白原因..

 createSearchViewObservable(searchView)
            .subscribeOn(Schedulers.io())
            .observeOn(AndroidSchedulers.mainThread())
            .concatMap(new Func1<String, Observable<MoviesWrapper>>() {
                @Override
                public Observable<MoviesWrapper> call(String title) {
                    RestMovieSource repo = new RestMovieSource();
                   return repo.searchMovieByTitle(title);
                }
            })
            .subscribe(new Subscriber<MoviesWrapper>() {
                @Override
                public void onCompleted() {

                }

                @Override
                public void onError(Throwable e) {
                    e.printStackTrace();
                    Toast.makeText(getContext(), e.getCause().getMessage(), Toast.LENGTH_SHORT).show();
                }

                @Override
                public void onNext(MoviesWrapper moviesWrapper) {
                    for (Movie movie : moviesWrapper.getResults()) {
                        Toast.makeText(getContext(), movie.getTitle(), Toast.LENGTH_SHORT).show();
                    }
                }
            });

D/OkHttp: --> GET /3/search/movie?api_key=xxxx&query=Jurassic%20World HTTP/1.1
D/OkHttp: --> END GET

  android.os.NetworkOnMainThreadException
      at android.os.StrictMode$AndroidBlockGuardPolicy.onNetwork(StrictMode.java:1147)
      at java.net.InetAddress.lookupHostByName(InetAddress.java:418)
      at java.net.InetAddress.getAllByNameImpl(InetAddress.java:252)
      at java.net.InetAddress.getAllByName(InetAddress.java:215)
      at com.squareup.okhttp.Dns.lookup(Dns.java:39)
      at com.squareup.okhttp.internal.http.RouteSelector.resetNextInetSocketAddress(RouteSelector.java:184)
      at com.squareup.okhttp.internal.http.RouteSelector.nextProxy(RouteSelector.java:153)
      at com.squareup.okhttp.internal.http.RouteSelector.next(RouteSelector.java:95)
      at com.squareup.okhttp.internal.http.HttpEngine.createNextConnection(HttpEngine.java:345)
      at com.squareup.okhttp.internal.http.HttpEngine.connect(HttpEngine.java:328)
      at com.squareup.okhttp.internal.http.HttpEngine.sendRequest(HttpEngine.java:246)
      at com.squareup.okhttp.Call.getResponse(Call.java:276)
      at com.squareup.okhttp.Call$ApplicationInterceptorChain.proceed(Call.java:234)
      at com.squareup.okhttp.logging.HttpLoggingInterceptor.intercept(HttpLoggingInterceptor.java:180)
      at com.squareup.okhttp.Call$ApplicationInterceptorChain.proceed(Call.java:223)
      at com.squareup.okhttp.Call.getResponseWithInterceptorChain(Call.java:196)
      at com.squareup.okhttp.Call.execute(Call.java:79)
      at retrofit.OkHttpCall.execute(OkHttpCall.java:116)
      at retrofit.RxJavaCallAdapterFactory$CallOnSubscribe.call(RxJavaCallAdapterFactory.java:111)
      at retrofit.RxJavaCallAdapterFactory$CallOnSubscribe.call(RxJavaCallAdapterFactory.java:88)
      at rx.Observable.call(Observable.java:162)
      at rx.Observable.call(Observable.java:154)
      at rx.Observable.call(Observable.java:162)
      at rx.Observable.call(Observable.java:154)
      at rx.Observable.unsafeSubscribe(Observable.java:8171)
      at rx.internal.operators.OperatorConcat$ConcatSubscriber.subscribeNext(OperatorConcat.java:172)
      at rx.internal.operators.OperatorConcat$ConcatSubscriber.onNext(OperatorConcat.java:136)
      at rx.internal.operators.OperatorConcat$ConcatSubscriber.onNext(OperatorConcat.java:79)
      at rx.internal.operators.OperatorMap.onNext(OperatorMap.java:54)
      at rx.internal.operators.OperatorObserveOn$ObserveOnSubscriber.pollQueue(OperatorObserveOn.java:202)
      at rx.internal.operators.OperatorObserveOn$ObserveOnSubscriber.call(OperatorObserveOn.java:162)
      at rx.internal.schedulers.ScheduledAction.run(ScheduledAction.java:55)
      at android.os.Handler.handleCallback(Handler.java:739)
      at android.os.Handler.dispatchMessage(Handler.java:95)
      at android.os.Looper.loop(Looper.java:135)
      at android.app.ActivityThread.main(ActivityThread.java:5221)
      at java.lang.reflect.Method.invoke(Native Method)
      at java.lang.reflect.Method.invoke(Method.java:372)
      at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:899)
      at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:694)

Answer 1

只需在 concatMap():

之后调用 subscribeOn()

createSearchViewObservable(searchView)
        .concatMap(new Func1<String, Observable<MoviesWrapper>>() {
            @Override
            public Observable<MoviesWrapper> call(String title) {
                RestMovieSource repo = new RestMovieSource();
                return repo.searchMovieByTitle(title);
            }
        })
        .subscribeOn(Schedulers.io())
        .observeOn(AndroidSchedulers.mainThread())
        .subscribe(new Subscriber<MoviesWrapper>() {
            @Override
            public void onCompleted() {

            }

            @Override
            public void onError(Throwable e) {
                e.printStackTrace();
                Toast.makeText(getContext(), e.getCause().getMessage(), Toast.LENGTH_SHORT).show();
            }

            @Override
            public void onNext(MoviesWrapper moviesWrapper) {
                for (Movie movie : moviesWrapper.getResults()) {
                    Toast.makeText(getContext(), movie.getTitle(), Toast.LENGTH_SHORT).show();
                }
            }
        });

Answer 2

我解决了为从 concatMap() 返回的可观察对象定义 subscribeOn 和 observeOn 的问题。外面的 subscribeOn/observeOn 仅特定于来自 createSearchViewObservable(searchView) 的第一个可观察对象。

 createSearchViewObservable(searchView)
        .subscribeOn(Schedulers.io())
        .observeOn(AndroidSchedulers.mainThread())
        .concatMap(new Func1<String, Observable<MoviesWrapper>>() {
            @Override
            public Observable<MoviesWrapper> call(String title) {
                RestMovieSource repo = new RestMovieSource();
               return repo.searchMovieByTitle(title)
                      .subscribeOn(Schedulers.io())  
                      .observeOn(AndroidSchedulers.mainThread());;
            }
        })
        .subscribe(...)

Answer 3

ConcatMap 或 flatMap 将生成一个新的 observable，它从旧的 observable 获取数据。因此，您将调度程序设置为旧的可观察对象，而不是新的。

使用 Retrofit 2 和 RxJava 的 concatMap() 中的 NetworkOnMainThreadException

NetworkOnMainThreadException in concatMap() with Retrofit 2 and RxJava

android

rx-java

retrofit