麻烦高手帮忙看一上，为什么不能监听键盘事件

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

public class Pete extends JFrame {
    PetePanel pete = new PetePanel();

    public Pete() {
        super("Pixel Pete");
        setSize(500, 500);
        setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        JPanel pane = new JPanel();
        pane.setLayout(new GridLayout(1, 1, 15, 15));
        pane.add(pete);
        this.addKeyListener(new KeyAdapter(){//没有得到焦点，放frame容易获取焦点。
            @Override
            public void keyPressed(KeyEvent e) {
                System.out.println("ppppp");
                if (e.getKeyCode() == KeyEvent.VK_LEFT) {
                    pete.current = 1;
                    pete.x =pete.x - 10;
                } else if (e.getKeyCode() == KeyEvent.VK_RIGHT) {
                    pete.current = 0;
                    pete.x = pete.x + 10;
                } else if (e.getKeyCode() == KeyEvent.VK_UP) {
                    pete.current = 2;
                    pete.y = pete.y - 10;
                } else if (e.getKeyCode() == KeyEvent.VK_DOWN) {
                    pete.current = 3;
                    pete.y = pete.y - 10;
                }
                repaint();
            }

            public void keyTyped(KeyEvent e){
                System.out.println("kkkkk");
            }

            public void keyReleased(KeyEvent e) {
                System.out.println("rrrrrr");
            }
        });
        setContentPane(pane);
        this.setVisible(true);
        this.requestFocus();//具体办法可以手设焦点。如果焦点有问题，就优先想到它
    }

    public static void main(String[] arguments) {
        Pete Penguin = new Pete();
        PetePanel a = new PetePanel();
    }
}

class PetePanel extends JPanel{
    // JPanel.requestFocus();
    // Thread runner;
    Image petePics[] = new Image[4];
    Image back;
    int current = 0;
    int x = 100;
    int y = 100;

    PetePanel() {
        super();
        setBackground(Color.black);
        String peteSrc[] = { "right.jpg", "left.jpg", "up.jpg", "down.jpg" };
        Toolkit kit = Toolkit.getDefaultToolkit();
        for (int i = 0; i < petePics.length; i++) {
            petePics[i] = kit.getImage(peteSrc[i]);
        }
        back = kit.getImage("abc.bmp");
        // if(runner==null)
        // {
        // runner=new Thread(this);
        // runner.start();
        // }

    }

    public void paint(Graphics comp) {
        Graphics2D comp2D = (Graphics2D) comp;
        // if(back!=null)
        // comp2D.drawImage(back,0,0,this);
        comp2D.setColor(Color.black);
        comp2D.fillRect(0, 0, 500, 500);
        if (petePics[current] != null)
            comp2D.drawImage(petePics[current], x, y, this);
    }

    public void fun() {
        for (int i = 0; i < 500; i++) {
            x = x + 5;
            current = 1;
            repaint();
        }
        
    }
}