package wintys.event;
import javax.swing.event.EventListenerList;
import java.util.Date;
import java.text.DateFormat;
import java.text.SimpleDateFormat;

/**
* Java的事件機制/自定義事件.

運行結果:
do something interesting in source here.
listener detects [event]:wintys.event.MyEvent[source=wintys.event.MySource@18158
59] [occur at]:2009-10-11 16:27:49
listener detects [event]:wintys.event.MyEvent[source=wintys.event.MySource@18158
59] [occur at]:2009-10-11 16:27:49

* @version 2009-10-11
* @author 天堂露珠 (wintys@gmail.com)
* @see http://www.aygfsteel.com/wintys
*/
class MyEventTest{
    public static void main(String[] args){
        MySource source = new MySource();
        MyListener myListener = new MyListener(){
            public void doMyAction(MyEvent e){
                System.out.println("listener detects " + e);
            }
        };
        source.addMyListener(myListener);
        source.addMyListener(myListener);
        source.addMyListener(myListener);
        source.removeMyListener(myListener);

        source.doSomething();
    }
}

/**
* 自定義的事件.
* @version 2009-10-11
* @author 天堂露珠(wintys@gmail.com)
* @see http://www.aygfsteel.com/wintys
*/
class MyEvent extends java.util.EventObject{
    private Date date;//記錄事件發生的時間

    public MyEvent(Object source , Date date){
        super(source);

        this.date = date;
    }

    public String toString(){
        DateFormat df = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");
        String dt = df.format(date);

        return "[event]:" + super.toString() + " [occur at]:" + dt;
    }
}

/**
* 自定義事件監聽器接口.
* @version 2009-10-11
* @author 天堂露珠(wintys@gmail.com)
* @see http://www.aygfsteel.com/wintys
*/
interface MyListener extends java.util.EventListener{
    void doMyAction(MyEvent e);
}

/**
* 自定義事件源.
* @version 2009-10-11
* @author 天堂露珠(wintys@gmail.com)
* @see http://www.aygfsteel.com/wintys
*/
class MySource{
    /**
     * 保存注冊的監聽器列表.
     * 子類可以使用它保存自己的事件監聽器(非MyListener監聽器)列表.
     */
    protected EventListenerList listenerList = new EventListenerList();
    private MyEvent myEvent = null;//fireDoMyAction()使用此變量

    /**
     * 沒有做任何事
     */
    public MySource(){
    }
    /**
     * 添加一個MyListener監聽器
     */
    public void addMyListener(MyListener listener){
        listenerList.add(MyListener.class , listener);
    }

    /**
     * 移除一個已注冊的MyListener監聽器.
     * 如果監聽器列表中已有相同的監聽器listener1、listener2,
     * 并且listener1==listener2,
     * 那么只移除最近注冊的一個監聽器。
     */
    public void removeMyListener(MyListener listener){
        listenerList.remove(MyListener.class , listener);
    }

    /**
     * @return 在此對象上監聽的所有MyListener類型的監聽器
     */
    public MyListener[] getMyListeners(){
        return (MyListener[])listenerList.getListeners(MyListener.class);
    }

    //Winty:Copy directly from javax.swing.event.EventListenerList
    /*Notify all listeners that have registered interest for
       notification on this event type.  The event instance
       is lazily created using the parameters passed into
       the fire method.
     */
    protected void fireDoMyAction() {
         // getListenerList() Guaranteed to return a non-null array
         Object[] listeners = listenerList.getListenerList();
         // Process the listeners last to first, notifying
         // those that are interested in this event
        for (int i = listeners.length-2; i>=0; i-=2) {
            if (listeners[i]==MyListener.class) {
                // Lazily create the event:
                if (myEvent == null)
                    myEvent = new MyEvent(this , new Date());
                ((MyListener)listeners[i+1]).doMyAction(myEvent);
            }
        }
    }

    /**
     * 做一些事件源應該做的有意義的事，然后通知監聽器.
     * 這里只是一個示例方法.
     * 例如:MySource如果是一個按鈕，則doSomething()就可以命名為click(),
     * 當用戶點擊按鈕時調用click()方法.
     */
    public void doSomething() {
        System.out.println("do something interesting here.");

        fireDoMyAction();//通知監聽器
    }
}