public class RxBus {
    private final Subject<Object, Object> bus;
    // PublishSubject只会把在订阅发生的时间点之后来自原始Observable的数据发射给观察者
    private RxBus() {
        bus = new SerializedSubject<>(PublishSubject.create());
    }

    public static RxBus getDefault() {
        return RxBusHolder.sInstance;
    }

    private static class RxBusHolder {
        private static final RxBus sInstance = new RxBus();
    }

    // 提供了一个新的事件
    public void post(Object o) {
        bus.onNext(o);
    }

    // 根据传递的 eventType 类型返回特定类型(eventType)的 被观察者
    public <T> Observable<T> toObservable(Class<T> eventType) {
        return bus.ofType(eventType);
    }
}

void registerEvent() {
        Subscription rxSubscription = RxBus.getDefault().toObservable(NightModeEvent.class)
                .compose(RxUtil.<NightModeEvent>rxSchedulerHelper())
                .map(new Func1<NightModeEvent, Boolean>() {
                    @Override
                    public Boolean call(NightModeEvent nightModeEvent) {
                        return nightModeEvent.getNightMode();
                    }
                })
                .subscribe(new Observer<Boolean>() {
                    @Override
                    public void onCompleted() {

                    }

                    @Override
                    public void onError(Throwable e) {
                        mView.showError("切换模式失败ヽ(≧Д≦)ノ");
                    }

                    @Override
                    public void onNext(Boolean aBoolean) {
                        mView.useNightMode(aBoolean);
                    }
                });
        addSubscrebe(rxSubscription);
    }

  public static <T> Observable.Transformer<T, T> rxSchedulerHelper() {    //compose简化线程
        return new Observable.Transformer<T, T>() {
            @Override
            public Observable<T> call(Observable<T> observable) {
                return observable.subscribeOn(Schedulers.io())
                        .observeOn(AndroidSchedulers.mainThread());
            }
        };
    }