Swing设置透明问题

[年轻的魅力]

我编写了一个Swing登录框，有设置背景，但是外层的jpanel会把背景覆盖掉，感觉很丑，要怎么设置透明，各位大神帮帮忙！
代码如下：

public class UserLogin extends JFrame{

private Graphics g;

//构造函数
public UserLogin(){
//加载背景图片
final ImageIcon icon = new ImageIcon("D:\\workspace\\images\\bg_login.jpg");
JPanel container = new JPanel() {
public void paintComponent(Graphics g) {
super.paintComponent(g);
Graphics2D g2d = (Graphics2D) g;
if(icon != null){
g2d.drawImage(icon.getImage(), 0, 0, getWidth(), this.getHeight(), this);
}
}
};

//logo图片
JLabel lblIamge = new JLabel();
ImageIcon admin_p = new ImageIcon("D:\\workspace\\images\\admin_p.gif");
lblIamge.setIcon(admin_p);

//用户名、密码、登录
JTextField tfUserName = new JTextField(15);
JPasswordField pfPassword = new JPasswordField(15);
JButton bntLogin = new JButton("登录");
tfUserName.setBackground(null);
tfUserName.setOpaque(false);
pfPassword.setOpaque(false);

JPanel center_right = new JPanel();

center_right.setLayout(new GridLayout(3,1,10,10));
center_right.setBackground(null);
center_right.setOpaque(false);
center_right.add(tfUserName);
center_right.add(pfPassword);
center_right.add(bntLogin);


JPanel center = new JPanel();
center.add(lblIamge);
center.add(center_right);


container.add(center);

//this.setBounds(0,0,400,300);
this.setSize(400,300); //设置窗口大小
this.setLocationRelativeTo(null); //设置窗口居中
this.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
this.setContentPane(container);
this.setVisible(true);

}

public static void main(String[] args){
SwingUtilities.invokeLater(new Runnable() {

@Override
public void run() {
new UserLogin();

}
});
}

运行后的效果：

[oh_Maxy]

http://blog.163.com/lh_bbs/blog/static/143070803201108213037/ http://bbs.csdn.net/topics/370132863 这两个地方都有讨论。

[爱跳舞的铅笔头]

你把Jpanel的Background设为Null应该就变成透明了，试一下！

[yanghongjy]

最简单，jpane 上面放 jlabel 显示图片，文本框方上面, ok