1、定義一個 ValueChangedEvent
ValueChangedEvent用於在設置屬性值的時候，觸發事件。
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、定義監聽接口 ValueChangeListener
ValueChangeListener 提供屬性值變化的接口。
package org.teamlet;
public interface ValueChangeListener extends java.util.EventListener {
public abstract void performed(ValueChangeEvent e);
}
3、事件的產生者
EventProducer提供了監聽容器listenerRegister，負責消費者的注冊。
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、注冊器
ListenerRegister負責注冊和分發事件。
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、事件的消費者
EventConsumer實現ValueChangedListener，當EventProducer 發送事件時，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
來源：CSDN
原文：https://blog.csdn.net/teamlet/article/details/42618733
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