java监听器演示样例

监听器的原理是观察者模式。就像明星（事件源）聚拢了一群粉丝（观察者）。当明星有啥举动的时候会通过粉丝们报道出去。

订阅信息、计算器button都是该原理的应用。

以下写了一个监听器的小样例：

package listener;

import java.util.EventObject;

/**

 * 定义事件对象,用于标记当前进行的动作。必须继承EventObject。

 * @author zyj

 *

 */

public class StateEvent extends EventObject {





private static final long serialVersionUID = 5323292975415079206L;



private Enum<ActionEnum> action;



public StateEvent(Object source, Enum<ActionEnum> action) {

super(source);

this.action = action;

}





public Enum<ActionEnum> getAction() {

return action;

}





public void setAction(Enum<ActionEnum> action) {

this.action = action;

}



}

package listener;

public enum ActionEnum {

wake,sleep;

}

package listener;

import java.util.EventListener;

/**

 * 定义监听接口，负责监听StateEvent事件。

必须继承EventListener。

* @author zyj

 *

 */

public interface StateListener extends EventListener {

void handleState(StateEvent event);

}

package listener;

public class WakeListener implements StateListener {



@Override

public void handleState(StateEvent event) {

if(event.getAction() != null && event.getAction().equals(ActionEnum.wake)){

System.out.println("你醒了。");

}

}



}

package listener;

public class SleepListener implements StateListener {



@Override

public void handleState(StateEvent event) {

if(event.getAction() != null && event.getAction().equals(ActionEnum.sleep)){

System.out.println("你睡了！");

}

}



}

package listener;

import java.util.ArrayList;

import java.util.List;



public class StateManager {

private List<StateListener> list = new ArrayList<StateListener>();



public boolean addListener(StateListener listener){

if(listener == null)

return false;

return list.add(listener);

}



public boolean removeListener(StateListener listener){

if(listener == null)

return false;

return list.remove(listener);

}



private void notifyAllListeners(StateEvent event){

for(StateListener listener : list){

listener.handleState(event);

}

}



public void wake(){

StateEvent event = new StateEvent(this, ActionEnum.wake);

notifyAllListeners(event);

}



public void sleep(){

StateEvent event = new StateEvent(this, ActionEnum.sleep);

notifyAllListeners(event);

}



}

package listener;

public class ListenerTest {

public static void main(String[] args) {

StateManager manager = new StateManager();

manager.addListener(new WakeListener());

manager.addListener(new SleepListener());

manager.wake();

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

manager.sleep();

}

}