在 Observables 中包装事件监听器 [英] Wrapping event listeners in Observables

问题描述

我看过很多关于如何将有限的事物(如数组或 Iterables)转换为 Observables 的例子，但我不确定我是否理解如何将Observable 用像事件接收器这样的活动且有效无界的东西制作出来.我研究了 RxJava2 文档并提出了这个，以 Android LocationListener 为例.

I've seen a lot of examples of how to turn finite things like arrays or Iterables into Observables, but I'm not sure I understand how to make an Observable out of something live and effectively unbounded like an event receiver. I studied the RxJava2 docs and came up with this, using an Android LocationListener as an example.

是否有更简单和/或更正确的方法来做到这一点?我知道RxBus"概念，但这似乎是一种坚持旧事件总线范式的方式.

Is there a simpler and/or more correct way to do this? I'm aware of the "RxBus" concept, but it seems like a way of clinging to the old event bus paradigm.

final Observable<Location> locationObservable = Observable.create(new ObservableOnSubscribe<Location>() {
    final LocationManager mLocationManager = (LocationManager) getSystemService(LOCATION_SERVICE);

    @Override
    public void subscribe(final ObservableEmitter<Location> emitter) throws Exception {
        final LocationListener listener = new LocationListener() {
            @Override
            public void onLocationChanged(final Location location) {
                emitter.onNext(location);
            }

            @Override
            public void onStatusChanged(final String s, final int i, final Bundle bundle) {
                // TODO ???
            }

            @Override
            public void onProviderEnabled(final String s) {
                // TODO ???
            }

            @Override
            public void onProviderDisabled(final String s) {
                // TODO ???
            }
        };

        mLocationManager.requestLocationUpdates(LocationManager.GPS_PROVIDER, 0, 0, listener);

        emitter.setCancellable(new Cancellable() {
            @Override
            public void cancel() throws Exception {
                mLocationManager.removeUpdates(listener);
            }
        });

        emitter.setDisposable(new Disposable() {
            private AtomicBoolean mDisposed;

            @Override
            public void dispose() {
                if(mDisposed.compareAndSet(false, true)) {
                    mLocationManager.removeUpdates(listener);
                }
            }

            @Override
            public boolean isDisposed() {
                return mDisposed.get();
            }
        });
    }
});

推荐答案

using Observable.create() 确实是一个正确的方法.

using Observable.create() is indeed a correct way.

但是，对于 RxJava2，默认方式是扩展 Observable，您可以查看此答案了解更多详情.

However, with RxJava2 the default way is to extend an Observable, you can see this answer for greater details.

关于您的实施的一些评论:
- 没有必要同时设置Cancellable 和Disposable，因为后者会取消/处理第一个，你可以看到它们之间的区别此处.
- 我认为最好的做法是在开始收听更新之前注册可取消/一次性注册，以防止出现奇怪的边缘情况.

some comments though regarding your implementation:
- there is no point setting both Cancellable and Disposable, as the later one will cancel/dispose the first one, you can see the difference between them here.
- I think it's best practice, to register cancellable/disposable before you start listening to update, in order to prevent weird edge cases races.

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