我想在JFrame中或者Frame中添加一张背景图片，然后在这图片上画出会移动的小球，怎么实现？我的代码把添加背景图片去掉，小球就正常运行了，

怎么修改啊？

希望各位大侠指教

不胜感激！！！！

import java.awt.*;

import java.awt.event.*;

import javax.swing.*;

public class TestItem extends JFrame {

JLabel jl;

Bullet b = new Bullet(80,80);

public static void main(String[] args) {

new TestItem().lauchFrame();

}

public void lauchFrame() {

jl = new JLabel();

ImageIcon image = new ImageIcon("Images\\mainBack.png");

jl.setIcon(image);

jl.setBounds(0, 0, image.getIconWidth(), image.getIconHeight());

this.setTitle("坦克大战");

this.setSize(246, 350);

this.setVisible(true);

this.getLayeredPane().add(jl, new Integer(Integer.MIN_VALUE));

((JPanel)getContentPane()).setOpaque(false);

this.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

this.addWindowListener(new WindowAdapter() {

public void windowClosing(WindowEvent e) {

System.exit(0);

}

});

this.setBackground(Color.black);

new Thread(new paintThread()).start();

this.addKeyListener(new keyMonitor());

}

public void paint(Graphics g) {

b.draw(g);

}

private class paintThread implements Runnable {

public void run() {

while(true) {

repaint();

try {

Thread.sleep(80);

} catch (Exception e) {

e.printStackTrace();

}

}

}

}

private class keyMonitor extends KeyAdapter {

public void keyPressed(KeyEvent e) {

b.keyPressed(e);

}

public void keyReleased(KeyEvent e) {

b.keyReleased(e);

}

}

}

import java.awt.Color;

import java.awt.Graphics;

import java.awt.event.KeyEvent;

public class Bullet {

private int x;

private int y;

private static final int width = 16;

private static final int height = 16;

private static final int speed = 8;

Direction dir = Direction.D;

private boolean bU = false,bR = false,bD = false,bL = false;

public Bullet(int x, int y) {

this.x = x;

this.y = y;

}

public int getX() {

return x;

}

public void setX(int x) {

this.x = x;

}

public int getY() {

return y;

}

public void setY(int y) {

this.y = y;

}

public void draw(Graphics g) {

Color c = g.getColor();

g.setColor(Color.yellow);

g.fillOval(x, y, width, height);

g.setColor(c);

move();

}

private void move() {

switch(dir) {

case U:

y -= speed;

break;

case R:

x += speed;

break;

case D:

y += speed;

break;

case L:

x -= speed;

break;

}

}

public void keyPressed(KeyEvent e) {

switch(e.getKeyCode()) {

case KeyEvent.VK_UP:

bU = true;

break;

case KeyEvent.VK_RIGHT:

bR = true;

break;

case KeyEvent.VK_DOWN:

bD = true;

break;

case KeyEvent.VK_LEFT:

bL = true;

break;

}

licalDirection();

}

private void licalDirection() {

if(bU && !bR && !bD && !bL) {

dir = Direction.U;

} else if(!bU && bR && !bD && !bL) {

dir = Direction.R;

} else if(!bU && !bR && bD && !bL) {

dir = Direction.D;

} else if(!bU && !bR && !bD && bL) {

dir = Direction.L;

}

}

public void keyReleased(KeyEvent e) {

switch(e.getKeyCode()) {

case KeyEvent.VK_UP:

bU = false;

break;

case KeyEvent.VK_RIGHT:

bR = false;

break;

case KeyEvent.VK_DOWN:

bD = false;

break;

case KeyEvent.VK_LEFT:

bL = false;

break;

}

licalDirection();

}

}

public enum Direction {

U,R,D,L;

}