• 直接上代码 ，三个类

import rx.Observable;
import rx.functions.Func1;
import rx.subjects.PublishSubject;
import rx.subjects.SerializedSubject;
import rx.subjects.Subject;

/**
 * @author xzj
 * @date 2016/8/24 14:00.
 */
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 send(Object o, String tag) {
        mRxBusObserverable.onNext(new RxBusObject(tag, o));
    }

//    public Observable<Object> toObserverable() {
//        return mRxBusObserverable;
//    }

    public <T> Observable<T> toObservable(final Class<T> eventType, final String tag) {
        return mRxBusObserverable.filter(new Func1<Object, Boolean>() {
            @Override
            public Boolean call(Object o) {
                if (!(o instanceof RxBusObject)) return false;
                RxBusObject ro = (RxBusObject) o;
                return eventType.isInstance(ro.getObj()) && tag != null
                        && tag.equals(ro.getTag());
            }
        }).map(new Func1<Object, T>() {
            @Override
            public T call(Object o) {
                RxBusObject ro = (RxBusObject) o;
                return (T) ro.getObj();
            }
        });
    }

    /**
     * 判断是否有订阅者
     */
    public boolean hasObservers() {
        return mRxBusObserverable.hasObservers();
    }
}

/**
 * @author xzj
 * @date 2016/8/24 14:22.
 */
public class RxBusObject {
    private String tag;
    private Object obj;

    public RxBusObject(String tag, Object obj) {
        this.tag = tag;
        this.obj = obj;
    }

    public String getTag() {
        return tag;
    }

    public void setTag(String tag) {
        this.tag = tag;
    }

    public Object getObj() {
        return obj;
    }

    public void setObj(Object obj) {
        this.obj = obj;
    }

    public static RxBusObject newInstance(String tag, Object obj) {
        return new RxBusObject(tag, obj);
    }
}

/**
 * @author xzj
 * @date 2016/8/24 14:24.
 */

import rx.Subscriber;

/**
 * 请使用此类来subscribe RxBus返回的Observable以简化onError与onCompleted函数.
 */
public abstract class RxBusSubscriber<T> extends Subscriber<T> {
    @Override
    public void onCompleted() {
        completed();
    }

    @Override
    public void onError(Throwable e) {
        error(e);
    }

    @Override
    public void onNext(T t) {
        receive(t);
    }

    public abstract void receive(T data);
    public void error(Throwable e) {
        e.printStackTrace();
    }
    public void completed() {}

}

• 用法

Paste_Image.png

一个简单的例子
就是上下两个fragment，change按钮是在fragment里的，点击随机生成一个color发给下面的fragment2，下面的fragmeng2收到了，更改背景

public class MyFragment extends Fragment {
    @Nullable
    @Override
    public View onCreateView(LayoutInflater inflater, @Nullable ViewGroup container, @Nullable Bundle savedInstanceState) {
        View view = inflater.inflate(R.layout.layout_fragment, null);
        Button btn = (Button) view.findViewById(R.id.btn);

        btn.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                Random random = new Random();
                int color = Color.argb(random.nextInt(256), random.nextInt(256), random.nextInt(256), random.nextInt(256));
                RxBus.getInstance().send(color,"color");
            }
        });
        return view;
    }
}

public class MyFragment2 extends Fragment {

    private Subscription subscribe;

    @Nullable
    @Override
    public View onCreateView(LayoutInflater inflater, @Nullable ViewGroup container, @Nullable Bundle savedInstanceState) {
        final View view = inflater.inflate(R.layout.layout_fragment2, null);
        //标记发过来的是个int，tag是“color”，和被观测者send（）方法里参数能匹配上，才会被这里观测到
        subscribe = RxBus.getInstance().toObservable(Integer.class, "color") 
                .subscribe(new RxBusSubscriber<Integer>() {
                    @Override
                    public void receive(Integer data) {
                        view.setBackgroundColor(data);
                    }
                });
        return view;
    }

    @Override
    public void onDestroyView() {
        super.onDestroyView();
        if (!subscribe.isUnsubscribed()) {
            subscribe.unsubscribe();
        }
    }
}