我想问一下就是监听器都设置好了，为什么面板里面的小球动不了

Question

import java.awt.BorderLayout;
import java.awt.Color;
import java.awt.Graphics;
import java.awt.event.KeyEvent;
import java.awt.event.KeyListener;

import javax.swing.*;
class paint extends JPanel implements KeyListener{
int x=15;
int y=15;
public void paint(Graphics s){
s.fillOval(x, y, 15, 15);
}

    @Override
    public void keyTyped(KeyEvent e) {
        // TODO Auto-generated method stub
        switch(e.getKeyCode())  
        {  
            case KeyEvent.VK_UP:  
                y--;  
                //调用repaint()函数，重新绘制小球位置  
                this.repaint();  
                break;  
            case KeyEvent.VK_DOWN:  
                y++;  
                //调用repaint()函数，重新绘制小球位置  
                this.repaint();  
                break;  
            case KeyEvent.VK_LEFT:  
                x--;  
                //调用repaint()函数，重新绘制小球位置  
                this.repaint();  
                break;  
            case KeyEvent.VK_RIGHT:  
                x++;  
                //调用repaint()函数，重新绘制小球位置  
                this.repaint();  
                break;  
        }  

    }

    @Override
    public void keyPressed(KeyEvent e) {
        // TODO Auto-generated method stub

    }

    @Override
    public void keyReleased(KeyEvent e) {
        // TODO Auto-generated method stub

    }
}

public class controlBall{

public static void main(String[] args) {
    JFrame jf=new JFrame();
    jf.setSize(200,200);
    paint x=new paint();
    jf.add(x);
    jf.addKeyListener(x);
    jf.setVisible(true);


}

}

Answer 1

存在两个问题：
1 你应该重写paintComponent方法，否则你的面板上没有绘制圆点。
2 你应该实现的是keyPressed方法，而不是keyTyped方法。修正代码如下：

 @Override
    public void keyPressed(KeyEvent e) {
        // TODO Auto-generated method stub
        switch (e.getKeyCode()) {
        case KeyEvent.VK_UP:
            y--;
            // 调用repaint()函数，重新绘制小球位置
            this.repaint();
            break;
        case KeyEvent.VK_DOWN:
            y++;
            // 调用repaint()函数，重新绘制小球位置
            this.repaint();
            break;
        case KeyEvent.VK_LEFT:
            x--;
            // 调用repaint()函数，重新绘制小球位置
            this.repaint();
            break;
        case KeyEvent.VK_RIGHT:
            x++;
            // 调用repaint()函数，重新绘制小球位置
            this.repaint();
            break;
        }

    }

    @Override
    protected void paintComponent(Graphics g) {
        // TODO Auto-generated method stub
        super.paintComponent(g);

        g.fillOval(x, y, 15, 15);
    }

运行结果：

键盘上下都会改变黑点的位置，OK。赶紧采纳结题吧。