Java事件机制范例

java事件机制的参与者：

event object：事件对象，时间产生时具体的“事件”，一般作为listener的方法参数使用。

event source：事件源，接收事件的实体。

event listener：事件监听器类。当有对应的event object产生时，调用相应的方法进行处理。

事件对象：

/**
 * 事件对象类
 * 		继承EventObject类
 */
public class DoorEvent extends EventObject{
	private static final long serialVersionUID = 6734613668785304327L;
	
	private String state;
	
	public DoorEvent(Object source, String state) {
		super(source);
		this.state = state;
	}
	
	public String getState() {
		return state;
	}
	
	public void setState(String state) {
		this.state = state;
	}
}

事件监听器：

/**
 * 事件监听器接口类
 * 		继承EventListener接口
 */
public interface DoorEventListener extends EventListener{
	public void fireEvent(DoorEvent event);
}

/**
 * 开门事件监听器类
 */
public class DoorOpenEventListener implements DoorEventListener {
	@Override
	public void fireEvent(DoorEvent event) {
		if("open".equals(event.getState())){
			System.out.println("Door opened");
		}
	}
}

/**
 * 关门事件监听器类
 */
public class DoorCloseEventListener implements DoorEventListener {
	@Override
	public void fireEvent(DoorEvent event) {
		if("close".equals(event.getState())){
			System.out.println("Door closed!");
		}
	}
}

事件源：

/**
 * 事件源类
 */
public class DoorManager {
	private Set<DoorEventListener> listeners = new HashSet<DoorEventListener>();
	
	/**
	 * 注册事件
	 */
	public void addListener(DoorEventListener listener){
		listeners.add(listener);
	}
	
	/**
	 * 删除事件
	 */
	public void removeListener(DoorEventListener listener){
		listeners.remove(listener);
	}
	
	/**
	 * 通知所有注册的事件
	 * @param event 事件对象
	 */
	private void notifyListeners(DoorEvent event){
		Iterator<DoorEventListener> it = listeners.iterator();
        while (it.hasNext()) {
        	DoorEventListener listener = (DoorEventListener) it.next();
            listener.fireEvent(event);
        }
	}
	
	public void openDoor(){
		DoorEvent event = new DoorEvent(this, "open");
        notifyListeners(event);
	}
	
	public void closeDoor(){
		DoorEvent event = new DoorEvent(this, "close");
        notifyListeners(event);
	}
	
	public static void main(String[] args) {
		DoorManager dm = new DoorManager();
		dm.addListener(new DoorOpenEventListener());
		dm.addListener(new DoorCloseEventListener());
		
		dm.openDoor();
		dm.closeDoor();
	}
}