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 listeners = new Vector();

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 currentListeners = null;

synchronized (this) {

currentListeners = (Vector) 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 {

@Override

public 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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作者：teamlet

来源：CSDN

原文：https://blog.csdn.net/teamlet/article/details/42618733

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