jpane1_如何用另一个JPanel替换JPanel

我想用JFrame中的另一个替换Jpanel

我已经搜索并尝试了我的代码,但没有任何事情发生

这是我的代码：

public class Frame extends JFrame {

private Container contain;

private JPanel reChange,reChange2;

private JButton reChangeButton;

public Frame() {

super("Change a panel");

setSize(350, 350);

setLayout(null);

setLocationRelativeTo(null);

setResizable(false);

reChange = new JPanel(null);

reChange.setBackground(Color.red);

reChange.setSize(240, 225);

reChange.setBounds(50, 50, 240, 225);

add(reChange);

reChangeButton = new JButton("Change It");

reChangeButton.setBounds(20, 20, 100, 20);

add(reChangeButton);

reChangeButton.addActionListener(new ActionListener() {

@Override

public void actionPerformed(ActionEvent e) {

//System.out.println("in");

contain = getContentPane();

contain.removeAll();

//System.out.println("in2");

reChange2 = new JPanel(null);

reChange2.setBackground(Color.white);

reChange2.setSize(240, 225);

reChange2.setBounds(50, 50, 240, 225);

//System.out.println("in3");

contain.add(reChange2);

validate();

//System.out.println("in4");

setVisible(true);

//System.out.println("in5");

}

});

}

public static void main(String[] args) {

Frame frame = new Frame();

frame.setVisible(true);

frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

}

}

有人能帮我吗 ？非常感谢