觀察者:

public interface EventObserver<T> {

    void notifyData(T bean);
}

被觀察者:

public class EventObservable<T> {

    private List<EventObserver<T>> list = new ArrayList<>();
    public void register(EventObserver<T> eventObserver) {
        if (list == null || eventObserver == null
 
)
            return;
        synchronized (this) {
            if (!list.contains(eventObserver))
                list.add(eventObserver);
}
    }

    public void unregister(EventObserver<T> eventObserver) {
        if (list == null || list.size() == 0 || eventObserver == null)
            return;
 
        synchronized (this) {
            if (list.contains(eventObserver))
                list.remove(eventObserver);
}
    }

    public void notifyData(T bean) {
        if (list == null || list.size() == 0 || bean == null)
            return;
        for (EventObserver<T> eventObserver : list
 
) {
            eventObserver.notifyData(bean);
}
    }
}

測試bean:

public class EventBean {

    private String event;
    public EventBean() {
    }

    public EventBean(String event) {
        this.event = event;
}

    public String getEvent() {
        return event;
}

    public void setEvent(String event) {
        this.event = event;
}

    @Override
public String toString() {
        return "EventBean{" +
                "event='" + event + '\'' +
                '}';
}
}

使用方法:

EventObservable<EventBean> eventObservable = new EventObservable<>();
EventObserver<EventBean> eventObserver = new EventObserver<EventBean>() {
    @Override
public void notifyData(EventBean bean) {
        //do something
}
};
eventObservable.register(eventObserver);
eventObservable.notifyData(new EventBean("event"));