java中的事件处理_让小球上下左右移动

package com.event1;
//通过上下左右键，来控制一个小球的位置

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

public class CircleRun extends JFrame{

	MyPanel mp=null;
	
	public static void main(String[] args) {
		CircleRun cr=new CircleRun();		
	}
	public CircleRun(){
		mp=new MyPanel();
		this.add(mp);
		
		this.addKeyListener(mp);
		
		this.setSize(400,300);
		this.setVisible(true);
		this.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);		
	}	
}

//定义自己的面板
class MyPanel extends JPanel implements KeyListener{
	int x=10;
	int y=10;
	
	public void paint(Graphics g){
		super.paint(g);
		g.fillOval(x, y, 10, 10);
	}

	
	//键的一个值被输出	
	@Override
	public void keyTyped(KeyEvent e) {	
		
	}

	//键被按下
	@Override
	public void keyPressed(KeyEvent e) {
		//System.out.println("键被按下"+e.getKeyCode());
		if(e.getKeyCode()==KeyEvent.VK_DOWN){
			//System.out.println("12");
			y++;
		}else if(e.getKeyCode()==KeyEvent.VK_UP){
			y--;
		}else if(e.getKeyCode()==KeyEvent.VK_LEFT){
			x--;
		}else if(e.getKeyCode()==KeyEvent.VK_RIGHT){
			x++;
		}		
		//调用repaint()函数，来重绘界面
		this.repaint();
	}	
	//键被释放
	@Override
	public void keyReleased(KeyEvent e) {		
	}	
}