Luca S. Luca S. - 3 months ago 46
Android Question

NetworkOnMainThreadException in concatMap() with Retrofit 2 and RxJava

In my app I'm trying to use RxJava to react when the user search for a new movie and retrieve movie data from a webservice.
In order to do this I thought to use concatMap to concatenate the action of getting the new movie query to requesting the movie to the webservice.
Doing this I get a NetworkOnMainThread exception and I don't understand the reason..

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$1.lookup(Dns.java:39)
at com.squareup.okhttp.internal.http.RouteSelector.resetNextInetSocketAddress(RouteSelector.java:184)
at com.squareup.okhttp.internal.http.RouteSelector.nextProxy(RouteSelector.java:153)
at com.squareup.okhttp.internal.http.RouteSelector.next(RouteSelector.java:95)
at com.squareup.okhttp.internal.http.HttpEngine.createNextConnection(HttpEngine.java:345)
at com.squareup.okhttp.internal.http.HttpEngine.connect(HttpEngine.java:328)
at com.squareup.okhttp.internal.http.HttpEngine.sendRequest(HttpEngine.java:246)
at com.squareup.okhttp.Call.getResponse(Call.java:276)
at com.squareup.okhttp.Call$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$2.call(Observable.java:162)
at rx.Observable$2.call(Observable.java:154)
at rx.Observable$2.call(Observable.java:162)
at rx.Observable$2.call(Observable.java:154)
at rx.Observable.unsafeSubscribe(Observable.java:8171)
at rx.internal.operators.OperatorConcat$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$1.onNext(OperatorMap.java:54)
at rx.internal.operators.OperatorObserveOn$ObserveOnSubscriber.pollQueue(OperatorObserveOn.java:202)
at rx.internal.operators.OperatorObserveOn$ObserveOnSubscriber$2.call(OperatorObserveOn.java:162)
at rx.internal.schedulers.ScheduledAction.run(ScheduledAction.java:55)
at android.os.Handler.handleCallback(Handler.java:739)
at android.os.Handler.dispatchMessage(Handler.java:95)
at android.os.Looper.loop(Looper.java:135)
at android.app.ActivityThread.main(ActivityThread.java:5221)
at java.lang.reflect.Method.invoke(Native Method)
at java.lang.reflect.Method.invoke(Method.java:372)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:899)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:694)

Answer

I solved the problem defining subscribeOn and observeOn for the returning observable from the concatMap(). The subscribeOn/observeOn outside are specific only to the first observable from createSearchViewObservable(searchView).

 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(...)
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