Google EventBus 使用详解

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EventBus是Google.Guava提供的消息发布-订阅类库，它实现了观察者设计模式，消息通知负责人通过EventBus去注册/注销观察者，最后由消息通知负责人给观察者发布消息。

首先使用 maven 依赖：

<!-- https://mvnrepository.com/artifact/com.google.guava/guava -->        <dependency>            <groupId>com.google.guava</groupId>            <artifactId>guava</artifactId>            <version>19.0</version>        </dependency>

示例代码：

EventBusCenter.java

package com.lance.google.event.bus;import com.google.common.eventbus.EventBus;/** * Created by zhangzh on 2017/1/10. */public class EventBusCenter {    private static EventBus eventBus = new EventBus();    private EventBusCenter() {    }    public static EventBus getInstance() {        return eventBus;    }    public static void register(Object obj) {        eventBus.register(obj);    }    public static void unregister(Object obj) {        eventBus.unregister(obj);    }    public static void post(Object obj) {        eventBus.post(obj);    }}

观察者一

package com.lance.google.event.bus;import com.google.common.eventbus.Subscribe;/** * Created by zhangzh on 2017/1/10. */public class DataObserver1 {    /**     * 只有通过@Subscribe注解的方法才会被注册进EventBus     * 而且方法有且只能有1个参数     *     * @param msg     */    @Subscribe    public void func(String msg) {        System.out.println("String msg: " + msg);    }}

观察者二

package com.lance.google.event.bus;import com.google.common.eventbus.Subscribe;/** * Created by zhangzh on 2017/1/10. */public class DataObserver2 {    /**     * post() 不支持自动装箱功能,只能使用Integer,不能使用int,否则handlersByType的Class会是int而不是Intege     * 而传入的int msg参数在post(int msg)的时候会被包装成Integer,导致无法匹配到     */    @Subscribe    public void func(Integer msg) {        System.out.println("Integer msg: " + msg);    }}

代码测试

Test.java

package com.lance.google.event.bus;/** * Created by zhangzh on 2017/1/10. */public class Test {    public static void main(String[] args) throws InterruptedException {        DataObserver1 observer1 = new DataObserver1();        DataObserver2 observer2 = new DataObserver2();        EventBusCenter.register(observer1);        EventBusCenter.register(observer2);        System.out.println("============   start  ====================");        // 只有注册的参数类型为String的方法会被调用        EventBusCenter.post("post string method");        EventBusCenter.post(123);        System.out.println("============ after unregister ============");        // 注销observer2        EventBusCenter.unregister(observer2);        EventBusCenter.post("post string method");        EventBusCenter.post(123);        System.out.println("============    end           =============");    }}

输出结果:

============   start  ====================String msg: post string methodInteger msg: 123============ after unregister ============String msg: post string method============    end           =============

看使用起来简单吧!

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