Java event事件监听属性值变化 demo

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1、定义一个 ValueChangedEvent

ValueChangedEvent用于在设置属性值的时候，触发事件。

 package org.teamlet;import java.util.EventObject;public class ValueChangeEvent extends EventObject {/** *  */private static final long serialVersionUID = 767352958358520268L;private int value;public ValueChangeEvent(Object source) {this(source, 0);}public ValueChangeEvent(Object source, int newValue) {super(source);value = newValue;}public int getValue() {return value;}}

2、定义监听接口 ValueChangeListener

ValueChangeListener 提供属性值变化的接口。

 package org.teamlet;public interface ValueChangeListener extends java.util.EventListener {public abstract void performed(ValueChangeEvent e);}

3、事件的产生者

EventProducer提供了监听容器listenerRegister，负责消费者的注册。

 package org.teamlet;public class EventProducer {ListenerRegister register = new ListenerRegister();private int value;public int getValue() {return value;}public void setValue(int newValue) {if (value != newValue) {value = newValue;ValueChangeEvent event = new ValueChangeEvent(this, value);fireAEvent(event);}}public void addListener(ValueChangeListener a) {register.addListener(a);}public void removeListener(ValueChangeListener a) {register.removeListener(a);}public void fireAEvent(ValueChangeEvent event) {register.fireAEvent(event);}}

4、注册器

ListenerRegister负责注册和分发事件。

 package org.teamlet;import java.util.Vector;public class ListenerRegister {private Vector<ValueChangeListener> listeners = new Vector<ValueChangeListener>();public synchronized void addListener(ValueChangeListener a) {listeners.addElement(a);}public synchronized void removeListener(ValueChangeListener a) {listeners.removeElement(a);}@SuppressWarnings("unchecked")public void fireAEvent(ValueChangeEvent evt) {Vector<ValueChangeListener> currentListeners = null;synchronized (this) {currentListeners = (Vector<ValueChangeListener>) listeners.clone();}for (int i = 0; i < currentListeners.size(); i++) {ValueChangeListener listener = (ValueChangeListener) currentListeners.elementAt(i);listener.performed(evt);}}}

5、事件的消费者

EventConsumer实现ValueChangedListener，当EventProducer 发送事件时，接收事件。

 package org.teamlet;public class EventConsumer implements ValueChangeListener {@Overridepublic void performed(ValueChangeEvent e) {System.out.println("value changed, new value = " + e.getValue());}}

6、使用

 package org.teamlet;public class Main {public static void main(String[] args) {EventProducer producer = new EventProducer();producer.addListener(new EventConsumer());producer.setValue(2);}}

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