Answer by Shinoo Goyal for How do I fix 'android.os.NetworkOnMainThreadException'?

RxAndroid is another better alternative to this problem and it saves us from hassles of creating threads and then posting results on Android UI thread. We just need to specify threads on which tasks need to be executed and everything is handled internally.

Observable<List<String>> musicShowsObservable = Observable.fromCallable(new Callable<List<String>>() { 

  @Override 
  public List<String> call() { 
    return mRestClient.getFavoriteMusicShows(); 
  }
});

mMusicShowSubscription = musicShowsObservable
.subscribeOn(Schedulers.io())
.observeOn(AndroidSchedulers.mainThread())
.subscribe(new Observer<List<String>>() {

    @Override 
    public void onCompleted() { }

    @Override 
    public void onError(Throwable e) { }

    @Override 
    public void onNext(List<String> musicShows){
        listMusicShows(musicShows);
    }
});

1. By specifiying (Schedulers.io()),RxAndroid will run getFavoriteMusicShows() on a different thread.

2. By using AndroidSchedulers.mainThread() we want to observe this Observable on the UI thread, i.e. we want our onNext() callback to be called on the UI thread