相信大多数开发者都使用过EventBus或者Otto(我还未实践过)，作为事件总线通信库，如果你的项目已经加入RxJava和EventBus(或Otto)，那不妨用RxBus代替EventBus或者Otto，省去更多库的依赖。

RxJava

之前已经分享过RxJava知识，可以点击RxJava，这里不再细说。

RxBus

假设你已经对RxJava有所了解，再继续往下看。

public class RxBus {
    private static RxBus mRxBus = null;
    /**
     * 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 Subject<Object, Object> mRxBusObserverable = new SerializedSubject<>(PublishSubject.create());
    public static synchronized RxBus getInstance() {
        if (mRxBus == null) {
            mRxBus = new RxBus();
        }
        return mRxBus;
    }
    public void post(Object o) {
    if (hasObservers()) {
        mRxBusObserverable.onNext(o);
		}
    }
    public Observable<Object> toObserverable() {
        return mRxBusObserverable;
    }
    /**
     * 判断是否有订阅者
     */
    public boolean hasObservers() {
        return mRxBusObserverable.hasObservers();
    }
}

代码调用

先模拟一个订阅者，用hasObservers判断是否有订阅者，然后再发送。

public class RxBusActivity extends AppCompatActivity {
    private CompositeSubscription mCompositeSubscription;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_rx_bus);
        rxBusObservers();
        rxBusPost();
    }
    private void rxBusPost() {
        findViewById(R.id.button).setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                RxBus.getInstance().post(HandleEvent.getInstance());
            }
        });
    }
    public void addSubscription(Subscription subscription) {
        if (this.mCompositeSubscription == null) {
            this.mCompositeSubscription = new CompositeSubscription();
        }
        this.mCompositeSubscription.add(subscription);
    }
    private void rxBusObservers() {
        Subscription subscription = RxBus.getInstance()
                .toObserverable()
                .subscribeOn(Schedulers.io())
                .observeOn(AndroidSchedulers.mainThread())
                .subscribe(new Subscriber<Object>() {
                    @Override
                    public void onCompleted() {
                    }
                    @Override
                    public void onError(Throwable e) {
                    }
                    @Override
                    public void onNext(Object event) {
                        if (event instanceof HandleEvent) {
                            //do something
                            Log.d("wxl", "rxBusHandle");
                        }
                    }
                });
        addSubscription(subscription);
    }
    @Override
    protected void onDestroy() {
        super.onDestroy();
        Log.d("wxl", "onDestroy");
        if (this.mCompositeSubscription != null) {
		    //取消注册，以避免内存泄露
            this.mCompositeSubscription.unsubscribe();
        }
    }
}