以图片为背景在其上添加组件不被覆盖

import java.awt.*;


import javax.swing.*;
public class Why extends JFrame{
String str = "E:\图片\ps\bg3.jpg";
MyPanel mp1 = new MyPanel();
JLabel jl1 = new JLabel("hello");
JLabel jl2 = new JLabel("hello");
Why(){
mp1.setLayout(null);
setBounds(100, 100, 400, 400);
setDefaultCloseOperation(EXIT_ON_CLOSE);
add(mp1);
jl1.setBounds(10,10,40,20);
jl2.setBounds(40,40,40,20);
mp1.add(jl1);
mp1.add(jl2);
setVisible(true);

}
class MyPanel extends JPanel{
Image im = Toolkit.getDefaultToolkit().getImage(str);
public void paintComponent(Graphics g){
g.drawImage(im, 0, 0, null);
}
}
public static void main(String[] args){
new Why();
}


}import java.awt.*;


import javax.swing.*;
p