上下左右移动小球

import java.awt.Color;
import java.awt.event.*;
import java.awt.event.KeyListener; //必须要有这句话，且没办法自动import好奇怪
 
//import com.sun.glass.events.KeyEvent;不可以是这句
//import java.awt.event.*;  //必须要有这句话，且没办法自动import好奇怪
 
import java.awt.*;
 
public class MyBall{
	public static void main(String args[]){
		Frame w=new Frame();
		w.setSize(300,400);
		w.setBackground(Color.black);
		MyPanel mp=new MyPanel();
		w.add(mp);
	  //注册事件
		w.addKeyListener(mp);
		mp.addKeyListener(mp);	
		w.setVisible(true);
	}
}
class MyPanel extends Panel implements KeyListener{
//KeyListener鼠标右键"source-override implements methods
	int x=30;
	int y=30;
	public void paint(Graphics g){
		g.setColor(Color.WHITE);
		g.fillOval(x, y, 20, 20);	
	}
	@Override
	public void keyPressed(KeyEvent arg0){
		if(arg0.getKeyCode()==KeyEvent.VK_LEFT){
		   x--;
		}
		if(arg0.getKeyCode()==KeyEvent.VK_UP){
			y--;
		}
		if(arg0.getKeyCode()==KeyEvent.VK_RIGHT){
		     x++;	
		}	
		if(arg0.getKeyCode()==KeyEvent.VK_DOWN){
			 y++;	
			}	
		
		repaint();
	}
	@Override
	public void keyReleased(KeyEvent arg0){
	
	}
	@Override
	public void keyTyped(KeyEvent arg0){
		
	}
	  
	//public void keyReleased(KeyEvent arg0){
	//}
	//public void keyTyped(KeyEvent argo){
	//}
	
 }

 

另外一个正确代码

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) {		
	}	
}

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作者：hoho_12 
来源：优快云 
原文：https://blog.youkuaiyun.com/hoho_12/article/details/52004939 
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