如何在我的代码中更改JFrame屏幕？ 无法弄清楚

Question

I am trying to create RedPraire system that we use on my warehouse as a training and i am stuck for 3 days with changing from create account screen to error screen if you enter less than 3 characters. Am i missing something?

tried calling frame to make it not visible and make other visible also tried to just make it new JLabel somehow wouldnt work as well in actionPerformer...

    frameCreate.add(c1);
frameCreate.add(c2);
frameCreate.add(c4);
frameCreate.add(ca1);
frameCreate.add(pc1);
frameCreate.add(c5);
frameCreate.add(c99);
frameCreate.setVisible(true);
frameCreate.setSize(600, 450);
frameCreate.setResizable(false);
frameCreate.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frameCreate.setLocationRelativeTo(null);
frameCreate.getContentPane().setBackground(Color.black);

// ERROR USERNAME FRAME

c6 = new JLabel("Username too short. Press Enter");
c6.setBounds(250, 200, 100, 100);
frErrUs.add(c6);
frErrUs.setVisible(false);
frErrUs.setSize(600, 450);
frErrUs.setResizable(false);
frErrUs.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frErrUs.setLocationRelativeTo(null);
frErrUs.getContentPane().setBackground(Color.black);

}
public void actionPerformed(ActionEvent e) {
    String getT = e.getActionCommand();
    if(getT.length() < 3) {
        frameCreate.setVisible(false);
        frErrUs.setVisible(true);
    }

I've expected it to change beetween frames showing only error frame but cant really figure it out

Answer 1

If the frames do not appear/disappear as you expect, that suggests that your actionPerformed method is not being called. Check that the right add listener method has been called.

But instead of creating a second frame to display an error message, perhaps you should use a dialog. Here's a simple way to do that:

JOptionPane.showMessageDialog(frameCreate, "Username too short", "Error", JOptionPane.ERROR_MESSAGE);