参考
How do I display an image in the background of a Swing component?
http://www.jguru.com/faq/view.jsp?EID=9691
How do I display an image in the background of a Swing component?
http://www.jguru.com/faq/view.jsp?EID=9691
super.paintComponent(g);
// 下面开始用g画背景图片
....
}