background = new ImageIcon("images/backImage.png");
backImage = new JLabel(background);
backImage.setBounds(0, 0, background.getIconWidth(),
background.getIconHeight());
backPanel = (JPanel) this.getContentPane();
backPanel.setOpaque(false);
this.getLayeredPane().setLayout(null);
this.getLayeredPane().add(backImage, new Integer(Integer.MIN_VALUE));
backPanel.setLayout(new BorderLayout());
这个是我程序里面复制出来的,效果就下面图一样。