java中加深對事件處理機制

/*
 * 功能：加深對事件處理機制
 * 1、通過上下左右鍵來控制小球的位置
 * 
 */
package com.t3;

import javax.swing.*;
import java.awt.*;
import java.awt.event.*;

public class Demo3 extends JFrame {

	MyPanel mp=null;

	public static void main(String[] args) {
	
		Demo3 demo=new Demo3();

	}
	public Demo3()
	{
		mp=new MyPanel();
		this.add(mp);
		this.addKeyListener(mp);
		
		
		
		
		
		this.setTitle("會動的小球");
		this.setSize(400	,500);
		this.setLocation(20,20);
		
		this.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
		this.setVisible(true);
		
	}
	
}

//定義自己的面板
class MyPanel extends JPanel implements KeyListener
{
	
	int x=10;
	int y=10;
	public void paint(Graphics g)
	{
		super.paint(g);
		g.setColor(Color.red);
		g.fillOval(x, y, 30, 30);
	
	}

	
	//鍵被按下
	public void keyPressed(KeyEvent e) {
	
		//System.out.println("被按下"+e.getKeyCode());
		
		if(e.getKeyCode()==KeyEvent.VK_DOWN)
		{
			y+=5;
		}
		//調用repaint()函數，重新繪圖
		else if(e.getKeyCode()==KeyEvent.VK_UP)
		{
			
			y-=5;
		}
		else if(e.getKeyCode()==KeyEvent.VK_LEFT)
		{
			
			x-=5;
			
		}
		else if(e.getKeyCode()==KeyEvent.VK_RIGHT)
		{
			x+=5;

		}
		repaint();
	}


	//鍵被釋放
	public void keyReleased(KeyEvent e) {
	
		
	}

	//鍵的一個值被輸出
	public void keyTyped(KeyEvent e) {
	
		
	}
}