Accessing JFrame created in main from actionlistener

Question

I've created a frame (mainframe) for my program in the main class which I want to add and remove panels from in order switch between different screens of my program. The first screen of my program is the login panel which has a start button. When I press the start button I want to switch to the menu frame.

The removeAll method seems to work fine since the login panel disappears, but nothing appears in its place when I use the add, validate and repaint methods. I have tried to refer explicitly to the mainframe in the actionlistener (i.e. mainframe.add(menu)) but it does not recognise the object.

Thanks in advance!

public class Main {

    public static JFrame mainframe = new JFrame();

    public static void main(String[] args) {

        // Create mainframe to add and remove panels from
        LoginPanel lp = new LoginPanel();
        System.out.println("mainframe created!");

        // Set size of mainframe
        mainframe.setBounds(0, 0, 500, 500);
        mainframe.add(lp);

        // Get the size of the screen
        Dimension dim = Toolkit.getDefaultToolkit().getScreenSize();

        // Determine the new location of the mainframe
        int w = mainframe.getSize().width;
        int h = mainframe.getSize().height;
        int x = (dim.width-w)/2;
        int y = (dim.height-h)/2;

        // Move the mainframe
        mainframe.setLocation(x, y);
        mainframe.setVisible(true);     
    }
}

This is my login panel class:

public class LoginPanel extends JPanel {
    private JTextField usernameField;
    private JPasswordField passwordField;
    private final Action action = new SwingAction();

    /**
     * Create the panel.
     */
    public LoginPanel() {

        JButton btnLogin = new JButton("Login");
        btnLogin.addActionListener(new ActionListener() {
            public void actionPerformed(ActionEvent e) {
                String username = usernameField.getText();
                String password = new String (passwordField.getPassword());

                Login login = new Login();
                boolean Correct = login.isCorrect(username, password);
                **if (Correct == true){
                    removeAll();
                    Menu menu = new Menu();
                    add(menu);
                    validate();  
                    repaint();
                    setBounds(0, 0, 500, 500);
                    System.out.println("Attempted to start menu!");
                }**
            }
        });
        btnLogin.setAction(action);
        btnLogin.addMouseListener(new MouseAdapter() {
            @Override
            public void mouseClicked(MouseEvent arg0) {

        }});

}

Answer 1

I want to add and remove panels from in order switch between different screens of my program

Sounds like you should be using a Card Layout.

Answer 2

Define mainframe as a class field:

private JFrame mainframe;