Google Eventbus简单使用

    eventbus是Google Guava的事件订阅-发布组件。其特点是简单易用，需要编写的代码量很小，也不需要继承。

Pom依赖

<dependencies>
    <dependency>
        <groupId>com.google.guava</groupId>
        <artifactId>guava</artifactId>
        <version>20.0</version>
    </dependency>
</dependencies>

一. EventBus

　　google eventbus并没有强制要求使用单例的EventBus，而是可以自行创建，你可以在一个容器内拥有多个EventBus实例，当然也可以自行将其配置为单例。下面的代码是将EventBus配置成单例的

package study.yan.google.eventbus.demo;

import com.google.common.eventbus.EventBus;

public class EventBusCenter {
    private static EventBus eventBus = new EventBus();

    private EventBusCenter() {
    }

    public static EventBus getInstance(){
        return eventBus;
    }

    public static void register(Object object){
        eventBus.register(object);
    }

    public static void unregister(Object object){
        eventBus.unregister(object);
    }

    public static void post(Object object){
        eventBus.post(object);
    }
}

二. Observer

　　只需要在类的方法上加上@Subscribe注解即可

package study.yan.google.eventbus.demo;

import com.google.common.eventbus.Subscribe;

public class AdviceObserver1 {
    @Subscribe
    public void ff1(AdviceObserverEventArgs args) {
        System.out.println("ff2：" + args);
    }
}

package study.yan.google.eventbus.demo;

import com.google.common.eventbus.Subscribe;

public class AdviceObserver2 {
    @Subscribe
    public void ff1(AdviceObserverEventArgs args) {
        System.out.println("ff1：" + args);
    }
}

三. Publish

　　调用eventBus的post方法来发布一个事件

package study.yan.google.eventbus.demo;

public class Program {
    public static void main(String[] args) {
        DataObserver1 dataObserver1 = new DataObserver1();
        DataObserver2 dataObserver2 = new DataObserver2();

        EventBusCenter.register(dataObserver1);
        EventBusCenter.register(dataObserver2);

        EventBusCenter.post("a string");
        EventBusCenter.post(1);

        System.out.println("==============");

        EventBusCenter.unregister(dataObserver1);
        EventBusCenter.post("a string");
        EventBusCenter.post(1);

    }
}