How to set frame visibility conditionally in JSwing?

Question

I'm trying to create a login panel in Java Swing where the user will first get a screen that requires them to enter the credentials and if they match the correct credentials, they will be directed to another java GUI class called UserManager. I'm not sure how I can set the current frame (of the login panel) to be false and the set the frame visible of the new panel that I want to switch to (the UserManger panel) to be true.

Here is what I have so far but it's not working:

import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;

import javax.swing.JOptionPane;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.JLabel;
import javax.swing.JTextField;
import javax.swing.JPasswordField;
import javax.swing.JButton;

public class Main implements ActionListener {
  private static JLabel label;
  private static JTextField userText;
  private static JLabel passwordLabel;
  private static JPasswordField passwordText;
  private static JButton button;
  private static JLabel success;
  private static boolean loggedIn = false;
  
  public static void main(String[] args) {
    // JOptionPane.showMessageDialog(null, "Login");
    JFrame f = new JFrame();
    JPanel panel = new JPanel();
    f.setSize(100, 100);
    f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
    
    f.add(panel);

    panel.setLayout(null);
    // username text label
    label = new JLabel("User");
    label.setBounds(10, 20, 80, 25);
    panel.add(label);

    userText = new JTextField(20);
    userText.setBounds(100, 20, 165, 25);
    panel.add(userText);

    // pasword label
    passwordLabel = new JLabel("Password");
    passwordLabel.setBounds(10, 50, 80, 25);
    panel.add(passwordLabel);
    
    passwordText = new JPasswordField(20);
    passwordText.setBounds(100, 50, 165, 25);
    panel.add(passwordText);

    button = new JButton("Login");
    button.setBounds(10, 80, 80, 25);
    button.addActionListener(new Main());
    panel.add(button);

    success = new JLabel("");
    success.setBounds(10, 110, 300, 25);
    panel.add(success);
    

    f.setVisible(true);


    if (loggedIn) {
      UserManager frame = new UserManager();
      f.setVisible(false);
      frame.setVisible(true);
    }
    
  }

  @Override
  public void actionPerformed(ActionEvent e) {
    String user = userText.getText();
    String password = passwordText.getText();
    System.out.println(user + ", " + password);

    if(user.equals("John") && password.equals("hello")) {
      success.setText("Login successful");
      loggedIn = true;
    }
    else {
      success.setText("Incorrect credentials.");
    }
  }
}

Null layouts are a bad idea, instead learn how to use the layout manager apis. Use a CardLayoit to switch between different panels - this will require to isolate your ui into isolated workable units — MadProgrammer, Jan 29 '23 at 20:30
As an [example](https://stackoverflow.com/questions/15212418/swing-jpanel-switching-out-of-scope/15213177#15213177) — MadProgrammer, Jan 29 '23 at 20:35

score 1 · Answer 1 · answered Jan 29 '23 at 21:57

Use a `CardLayout`

See for How to Use CardLayout more details.

This will encourage you to isolate you functionality into individual components, there by isolating the workflows and supporting the "single responsibility" concept.

import java.awt.CardLayout;
import java.awt.EventQueue;
import java.awt.Font;
import java.awt.GridBagConstraints;
import java.awt.GridBagLayout;
import java.awt.Insets;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JOptionPane;
import javax.swing.JPanel;
import javax.swing.JPasswordField;
import javax.swing.JTextField;
import javax.swing.SwingUtilities;
import javax.swing.border.EmptyBorder;

public class Main {
    public static void main(String[] args) {
        new Main();
    }

    public Main() {
        EventQueue.invokeLater(new Runnable() {
            @Override
            public void run() {
                JFrame frame = new JFrame();
                frame.add(new MainPane());
                frame.pack();
                frame.setLocationRelativeTo(null);
                frame.setVisible(true);
            }
        });
    }

    public class MainPane extends JPanel {

        private UserPane userPane;
        private LoginPane loginPane;

        public MainPane() {
            setLayout(new CardLayout());

            userPane = new UserPane();
            loginPane = new LoginPane(new AuthenticationListener() {
                @Override
                public void authenticationWasSuccessful(User user) {
                    userPane.setUser(user);
                    // The user pane's content size will have changed
                    SwingUtilities.windowForComponent(userPane).pack();
                    ((CardLayout) getLayout()).show(MainPane.this, "USER");
                }

                @Override
                public void authenticationDidFail() {
                    JOptionPane.showMessageDialog(MainPane.this, "Authentication failed", "Error", JOptionPane.ERROR_MESSAGE);
                }
            });

            add(userPane, "USER");
            add(loginPane, "LOGIN");

            ((CardLayout) getLayout()).show(this, "LOGIN");
        }
    }

    public interface User {
        public String getName();
    }

    public class DefaultUser implements User {
        private String name;

        public DefaultUser(String name) {
            this.name = name;
        }

        @Override
        public String getName() {
            return name;
        }
    }

    public interface AuthenticationListener {
        public void authenticationWasSuccessful(User user);

        public void authenticationDidFail();
    }

    public class LoginPane extends JPanel {
        private JTextField user;
        private JPasswordField password;
        private JButton login;
        private AuthenticationListener loginListener;

        public LoginPane(AuthenticationListener listener) {
            setBorder(new EmptyBorder(32, 32, 32, 32));
            this.loginListener = listener;
            setLayout(new GridBagLayout());
            GridBagConstraints gbc = new GridBagConstraints();
            gbc.insets = new Insets(4, 4, 4, 4);
            gbc.gridx = 0;
            gbc.gridy = 0;
            gbc.anchor = GridBagConstraints.EAST;
            add(new JLabel("User name:"), gbc);
            gbc.gridy++;
            add(new JLabel("Password:"), gbc);

            gbc.gridx++;
            gbc.gridy = 0;
            gbc.anchor = GridBagConstraints.WEST;

            user = new JTextField(12);
            password = new JPasswordField(12);

            add(user, gbc);
            gbc.gridy++;
            add(password, gbc);

            login = new JButton("Login");

            gbc.gridx = 0;
            gbc.gridy++;
            gbc.anchor = GridBagConstraints.CENTER;
            gbc.gridwidth = GridBagConstraints.REMAINDER;
            add(login, gbc);

            login.addActionListener(new ActionListener() {
                @Override
                public void actionPerformed(ActionEvent e) {
                    boolean accept = (boolean) (((int) Math.round(Math.random() * 1)) == 0 ? true : false);
                    if (accept) {
                        loginListener.authenticationWasSuccessful(new DefaultUser(user.getText()));
                    } else {
                        loginListener.authenticationDidFail();
                    }
                }
            });
        }
    }

    public class UserPane extends JPanel {

        private JLabel userLabel;

        public UserPane() {
            JLabel label = new JLabel("Welcome!");
            Font font = label.getFont();
            label.setFont(font.deriveFont(Font.BOLD, 32));
            setLayout(new GridBagLayout());
            GridBagConstraints gbc = new GridBagConstraints();
            gbc.gridwidth = gbc.REMAINDER;
            add(label, gbc);

            userLabel = new JLabel();
            add(userLabel, gbc);
        }

        public void setUser(User user) {
            userLabel.setText(user.getName());
        }
    }
}

Use a modal `JDialog`

See How to Make Dialogs for more details.

More windows isn't always a good choice, but in the context of gathering user credentials, I think you can make an argument.

This makes use of a modal dialog to stop the code execution at the point that the window is made visible and it won't continue until the window is closed. This allows you an opportunity to get and validate the user credentials before the code continues (it's black magic in how it works, but it's a very common workflow)

import java.awt.EventQueue;
import java.awt.Font;
import java.awt.GridBagConstraints;
import java.awt.GridBagLayout;
import java.awt.Insets;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import javax.swing.JButton;
import javax.swing.JDialog;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JOptionPane;
import javax.swing.JPanel;
import javax.swing.JPasswordField;
import javax.swing.JTextField;
import javax.swing.border.EmptyBorder;

public class Main {
    public static void main(String[] args) {
        new Main();
    }

    public Main() {
        EventQueue.invokeLater(new Runnable() {
            @Override
            public void run() {
                User user = LoginPane.showLoginDialog();

                if (user != null) {
                    JFrame frame = new JFrame();
                    frame.add(new UserPane(user));
                    frame.pack();
                    frame.setLocationRelativeTo(null);
                    frame.setVisible(true);
                } else {
                    // Well, you really don't know do you?  Did they cancel
                    // the dialog or did authentication fail?
                }
            }
        });
    }

    public interface User {
        public String getName();
    }

    public static class DefaultUser implements User {
        private String name;

        public DefaultUser(String name) {
            this.name = name;
        }

        @Override
        public String getName() {
            return name;
        }
    }

    public static class LoginPane extends JPanel {
        public interface AuthenticationListener {
            public void authenticationWasSuccessful(User user);
            public void authenticationDidFail();
        }

        private JTextField userTextField;
        private JPasswordField passwordField;
        private JButton loginButton;

        private User user;

        public LoginPane(AuthenticationListener listener) {
            setBorder(new EmptyBorder(32, 32, 32, 32));
            setLayout(new GridBagLayout());
            GridBagConstraints gbc = new GridBagConstraints();
            gbc.insets = new Insets(4, 4, 4, 4);
            gbc.gridx = 0;
            gbc.gridy = 0;
            gbc.anchor = GridBagConstraints.EAST;
            add(new JLabel("User name:"), gbc);
            gbc.gridy++;
            add(new JLabel("Password:"), gbc);

            gbc.gridx++;
            gbc.gridy = 0;
            gbc.anchor = GridBagConstraints.WEST;

            userTextField = new JTextField(12);
            passwordField = new JPasswordField(12);

            add(userTextField, gbc);
            gbc.gridy++;
            add(passwordField, gbc);

            loginButton = new JButton("Login");

            gbc.gridx = 0;
            gbc.gridy++;
            gbc.anchor = GridBagConstraints.CENTER;
            gbc.gridwidth = GridBagConstraints.REMAINDER;
            add(loginButton, gbc);

            loginButton.addActionListener(new ActionListener() {
                @Override
                public void actionPerformed(ActionEvent e) {
                    boolean accept = (boolean) (((int) Math.round(Math.random() * 1)) == 0 ? true : false);
                    if (accept) {
                        user = new DefaultUser(userTextField.getText());
                        listener.authenticationWasSuccessful(user);
                    } else {
                        user = null;
                        listener.authenticationDidFail();
                    }
                }
            });
        }

        public User getUser() {
            return user;
        }

        public static User showLoginDialog() {
            JDialog dialog = new JDialog();
            dialog.setTitle("Login");
            dialog.setModal(true);

            LoginPane loginPane = new LoginPane(new LoginPane.AuthenticationListener() {
                @Override
                public void authenticationWasSuccessful(User user) {
                    dialog.dispose();
                }

                @Override
                public void authenticationDidFail() {
                    JOptionPane.showMessageDialog(dialog, "Authentication failed", "Error", JOptionPane.ERROR_MESSAGE);
                }
            });

            dialog.add(loginPane);
            dialog.pack();
            dialog.setLocationRelativeTo(null);
            dialog.setVisible(true);

            return loginPane.getUser();
        }
    }

    public class UserPane extends JPanel {
        public UserPane(User user) {
            setBorder(new EmptyBorder(32, 32, 32, 32));
            JLabel label = new JLabel("Welcome!");
            Font font = label.getFont();
            label.setFont(font.deriveFont(Font.BOLD, 32));
            setLayout(new GridBagLayout());
            GridBagConstraints gbc = new GridBagConstraints();
            gbc.gridwidth = gbc.REMAINDER;
            add(label, gbc);

            JLabel userLabel = new JLabel();
            userLabel.setText(user.getName());
            add(userLabel, gbc);
        }
    }
}

score 0 · Answer 2 · answered Jan 29 '23 at 20:46

0

You need to unset visibility of this frame and set visible User manager at the action performed level:

private navigateToNextFrame(){


f.dispose(false);
UserManager frame = new UserManager();
frame.setVisible(true);
}

Now you need to call this method in the action performed method instead of loggedin=true and delete block in main main method (if (loggedIn)) A little suggestion : User Manager could be a singleton so you can create it at least 1 time.

answered Jan 29 '23 at 20:46

Raf897

1

I'm a bit confused on where to put this code, when I put it just by itself it says that it requires a return type. Is there anything else I have to do? – Soccerball123 Jan 29 '23 at 21:26
Or, you could use a modal `JDialog` instead of a `JFrame` or you could make use `CardLayout` and avoid all the controversy over using multiple windows [The Use of Multiple JFrames: Good or Bad Practice?](https://stackoverflow.com/questions/9554636/the-use-of-multiple-jframes-good-or-bad-practice) – MadProgrammer Jan 29 '23 at 21:27
Sorry private void navigateToNextFrame(). – Raf897 Jan 30 '23 at 01:48

How to set frame visibility conditionally in JSwing?

2 Answers2

Use a CardLayout

Use a modal JDialog

Use a `CardLayout`

Use a modal `JDialog`