使用多个 JPanel 类时如何在 JFrame 中打开另一个 JPanel

Question

I have been looking for this for days now and I haven't found a solution so I just made my account.

I want to figure out how should I open another JPanel from the current JPanel in my JFrame. I have made three classes till now in the view package: mainView (JFrame), loginAs (JPanel), loginPanel (JPanel). What I want to do is, I want to display loginAs Panel as my first panel where user selects whether he is an Admin or Staff and then after clicking the desired option, it should open the loginPanel where they can log in. I'm stuck here as I don't know how I can give back the information to mainView that the user has selected Admin or Staff and that mainView should now move to the next panel that is loginPanel.

Here is the coding I did:

mainView

package view;

import java.awt.BorderLayout;
import java.awt.EventQueue;
import java.awt.Font;

import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JPanel;
import javax.swing.border.EmptyBorder;
import java.awt.CardLayout;
import java.awt.Color;

public class mainView extends JFrame {

    private JPanel contentPane;

    /**
     * Launch the application.
     */
    public static void main(String[] args) {
        EventQueue.invokeLater(new Runnable() {
            public void run() {
                try {
                    mainView frame = new mainView();
                    frame.setVisible(true);
                } catch (Exception e) {
                    e.printStackTrace();
                }
            }
        });
    }

    /**
     * Create the frame.
     */
    public mainView() {
        setTitle("COVID'19 Management System");
        setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        setBounds(100, 100, 550, 410);
        contentPane = new JPanel();
        contentPane.setBorder(new EmptyBorder(5, 5, 5, 5));
        setContentPane(contentPane);
        contentPane.setLayout(new CardLayout(0, 0));
        
        JPanel p1 = new loginAs();
        contentPane.add(p1, "t1");
        
        JPanel p2 = new loginPanel();
        contentPane.add(p2, "t2");
        
        JPanel p3 = new JPanel();
        contentPane.add(p3, "t3");
        
        JPanel p4 = new JPanel();
        contentPane.add(p4, "t4");
    }

}

loginAs

package view;

import java.awt.CardLayout;
import java.awt.Color;
import java.awt.Font;

import javax.swing.JButton;
import javax.swing.JLabel;
import javax.swing.JPanel;
import javax.swing.JTextField;
import view.mainView;

public class loginAs extends JPanel {

    /**
     * Create the panel.
     */
    public loginAs() {
        setBackground(Color.BLACK);
        setLayout(null);
        
        JLabel lblNewLabel = new JLabel("COVID'19 Management System");
        lblNewLabel.setForeground(Color.WHITE);
        lblNewLabel.setFont(new Font("Calibri", Font.BOLD, 18));
        lblNewLabel.setBounds(140, 27, 262, 28);
        add(lblNewLabel);
        
        JLabel lblNewLabel_1 = new JLabel("LOGIN AS");
        lblNewLabel_1.setForeground(Color.WHITE);
        lblNewLabel_1.setFont(new Font("Calibri", Font.BOLD, 16));
        lblNewLabel_1.setBounds(35, 87, 97, 28);
        add(lblNewLabel_1);
        
        JButton btnAdmin = new JButton("ADMIN");
        btnAdmin.setForeground(Color.BLACK);
        btnAdmin.setBackground(Color.WHITE);
        btnAdmin.setBounds(35, 134, 97, 39);
        add(btnAdmin);
        btnAdmin.setBorderPainted(false);
        btnAdmin.addMouseListener(new java.awt.event.MouseAdapter() {
            public void mouseEntered(java.awt.event.MouseEvent evt) {
                btnAdmin.setBackground(Color.GREEN);
            }

            public void mouseExited(java.awt.event.MouseEvent evt) {
                btnAdmin.setBackground(Color.WHITE);
            }

            public void mouseClicked(java.awt.event.MouseEvent e)
            {
                
            }
        });
        
        JButton btnStaff = new JButton("STAFF");
        btnStaff.setForeground(Color.BLACK);
        btnStaff.setBackground(Color.WHITE);
        btnStaff.setBounds(35, 200, 97, 39);
        add(btnStaff);
        btnStaff.setBorderPainted(false);
        btnStaff.addMouseListener(new java.awt.event.MouseAdapter() {
            public void mouseEntered(java.awt.event.MouseEvent evt) {
                btnStaff.setBackground(Color.GREEN);
            }

            public void mouseExited(java.awt.event.MouseEvent evt) {
                btnStaff.setBackground(Color.WHITE);
            }

            public void mouseClicked(java.awt.event.MouseEvent e)
            {
                
            }
        });
    }
}

loginPanel

package view;

import javax.swing.JPanel;
import javax.swing.JLabel;
import java.awt.Font;
import java.awt.Color;
import javax.swing.JTextField;
import javax.swing.JButton;

public class loginPanel extends JPanel {
    private JTextField txt_uname;
    private JTextField txt_pass;

    /**
     * Create the panel.
     */
    public loginPanel() {
        setBackground(Color.BLACK);
        setLayout(null);
        
        JLabel lblNewLabel = new JLabel("COVID'19 Management System");
        lblNewLabel.setForeground(Color.WHITE);
        lblNewLabel.setFont(new Font("Calibri", Font.BOLD, 18));
        lblNewLabel.setBounds(140, 27, 262, 28);
        add(lblNewLabel);
        
        JLabel lblNewLabel_1 = new JLabel("LOGIN PAGE");
        lblNewLabel_1.setForeground(Color.WHITE);
        lblNewLabel_1.setFont(new Font("Calibri", Font.BOLD, 16));
        lblNewLabel_1.setBounds(35, 87, 97, 28);
        add(lblNewLabel_1);
        
        JLabel lblNewLabel_2 = new JLabel("Username");
        lblNewLabel_2.setFont(new Font("Calibri", Font.BOLD, 14));
        lblNewLabel_2.setForeground(Color.WHITE);
        lblNewLabel_2.setBounds(35, 142, 74, 14);
        add(lblNewLabel_2);
        
        txt_uname = new JTextField();
        txt_uname.setBounds(123, 137, 147, 20);
        add(txt_uname);
        txt_uname.setColumns(10);
        
        JLabel lblNewLabel_2_1 = new JLabel("Password");
        lblNewLabel_2_1.setForeground(Color.WHITE);
        lblNewLabel_2_1.setFont(new Font("Calibri", Font.BOLD, 14));
        lblNewLabel_2_1.setBounds(35, 188, 74, 14);
        add(lblNewLabel_2_1);
        
        txt_pass = new JTextField();
        txt_pass.setColumns(10);
        txt_pass.setBounds(123, 183, 147, 20);
        add(txt_pass);
        
        JButton btn_login = new JButton("Login");
        btn_login.setBounds(123, 229, 89, 23);
        add(btn_login);

    }
}

Here is the visual representation:

Answer 1

I took your code, cleaned it up, and added an ActionListener for the JButtons on the first page.

Here's the GUI first page.

Here's the GUI second page.

The first thing I did was to get rid of the absolute positioning. I used a GridBagLayout on both JPanels .

The next thing I did was to factor out the button coloring on a mouse in and mouse out.

I created an application model to hold the variables I've seen. Eventually, this model will hold all the variables for the entire application.

I made all the classes inner classes so I can copy and paste this code into one block. You can and should separate my inner classes into separate classes.

Here's the complete runnable code.

import java.awt.BorderLayout;
import java.awt.CardLayout;
import java.awt.Color;
import java.awt.EventQueue;
import java.awt.Font;
import java.awt.GridBagConstraints;
import java.awt.GridBagLayout;
import java.awt.Insets;
import java.awt.LayoutManager;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.awt.event.MouseAdapter;
import java.awt.event.MouseEvent;

import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JPanel;
import javax.swing.JTextField;
import javax.swing.border.EmptyBorder;

public class Covid19GUI extends JFrame {

    private static final long serialVersionUID = 1L;

    /**
     * Launch the application.
     */
    public static void main(String[] args) {
        EventQueue.invokeLater(new Runnable() {
            public void run() {
                try {
                    new Covid19GUI();
                } catch (Exception e) {
                    e.printStackTrace();
                }
            }
        });
    }
    
    private Covid19Model model;

    private JPanel contentPane;

    /**
     * Create the frame.
     */
    public Covid19GUI() {
        this.model = new Covid19Model();
        
        setTitle("COVID'19 Management System");
        setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

        contentPane = new JPanel();
        contentPane.setBorder(new EmptyBorder(5, 5, 5, 5));
        contentPane.setLayout(new CardLayout(5, 5));

        JPanel p1 = new LoginAs(this, model);
        contentPane.add(p1, "t1");

        JPanel p2 = new LoginPanel(this, model);
        contentPane.add(p2, "t2");

        JPanel p3 = new JPanel();
        contentPane.add(p3, "t3");

        JPanel p4 = new JPanel();
        contentPane.add(p4, "t4");

        add(contentPane, BorderLayout.CENTER);
        pack();
        setLocationByPlatform(true);
        setVisible(true);
    }
    
    public JPanel getCardLayoutPanel() {
        return contentPane;
    }

    public class LoginAs extends JPanel {

        private static final long serialVersionUID = 1L;

        /**
         * Create the panel.
         */
        public LoginAs(Covid19GUI frame, Covid19Model model) {      
            setBackground(Color.BLACK);
            setLayout(new GridBagLayout());
            
            GridBagConstraints gbc = new GridBagConstraints();
            gbc.anchor = GridBagConstraints.CENTER;
            gbc.fill = GridBagConstraints.HORIZONTAL;
            gbc.insets = new Insets(5, 5, 5, 5);
            gbc.gridx = 0;
            gbc.gridy = 0;

            JLabel lblNewLabel = new JLabel("COVID'19 Management System");
            lblNewLabel.setForeground(Color.WHITE);
            lblNewLabel.setFont(new Font("Calibri", Font.BOLD, 18));
            add(lblNewLabel, gbc);

            gbc.gridy++;
            JLabel lblNewLabel_1 = new JLabel("LOGIN AS");
            lblNewLabel_1.setForeground(Color.WHITE);
            lblNewLabel_1.setFont(new Font("Calibri", Font.BOLD, 16));
            add(lblNewLabel_1, gbc);
            
            ButtonListener listener = new ButtonListener(frame, model);

            gbc.gridy++;
            JButton btnAdmin = new JButton("ADMIN");
            btnAdmin.addActionListener(listener);
            btnAdmin.addMouseListener(new ColorListener(btnAdmin));
            btnAdmin.setForeground(Color.BLACK);
            btnAdmin.setBackground(Color.WHITE);
            btnAdmin.setBorderPainted(false);
            add(btnAdmin, gbc);
            
            gbc.gridy++;
            JButton btnStaff = new JButton("STAFF");
            btnStaff.addActionListener(listener);
            btnStaff.addMouseListener(new ColorListener(btnStaff));         
            btnStaff.setForeground(Color.BLACK);
            btnStaff.setBackground(Color.WHITE);
            btnStaff.setBorderPainted(false);
            add(btnStaff, gbc);
        }
    }
    
    public class ColorListener extends MouseAdapter {
        
        private JButton button;
        
        public ColorListener(JButton button) {
            this.button = button;
        }

        @Override
        public void mouseEntered(MouseEvent evt) {
            button.setBackground(Color.GREEN);
        }

        @Override
        public void mouseExited(MouseEvent evt) {
            button.setBackground(Color.WHITE);
        }
    }
    
    public class ButtonListener implements ActionListener {
        
        private Covid19GUI frame;
        
        private Covid19Model model;

        public ButtonListener(Covid19GUI frame, Covid19Model model) {
            this.frame = frame;
            this.model = model;
        }

        @Override
        public void actionPerformed(ActionEvent event) {
            JButton button = (JButton) event.getSource();
            if (button.getText().equals("ADMIN")) {
                model.setAdmin(true);
            } else {
                model.setAdmin(false);
            }
            
            JPanel panel = frame.getCardLayoutPanel();
            CardLayout layout = (CardLayout) panel.getLayout();
            layout.show(panel, "t2");
        }
        
    }

    public class LoginPanel extends JPanel {

        private static final long serialVersionUID = 1L;
        
        private Covid19GUI frame;
        
        private Covid19Model model;

        private JTextField txt_uname;
        private JTextField txt_pass;

        /**
         * Create the panel.
         */
        public LoginPanel(Covid19GUI frame, Covid19Model model) {
            this.frame = frame;
            this.model = model;
            
            setBackground(Color.BLACK);
            setLayout(new GridBagLayout());
            
            GridBagConstraints gbc = new GridBagConstraints();
            gbc.anchor = GridBagConstraints.LINE_START;
            gbc.fill = GridBagConstraints.HORIZONTAL;
            gbc.insets = new Insets(5, 5, 5, 5);
            gbc.gridwidth = 2;
            gbc.gridx = 0;
            gbc.gridy = 0;

            JLabel lblNewLabel = new JLabel("COVID'19 Management System");
            lblNewLabel.setForeground(Color.WHITE);
            lblNewLabel.setFont(new Font("Calibri", Font.BOLD, 18));
            add(lblNewLabel, gbc);

            gbc.gridy++;
            JLabel lblNewLabel_1 = new JLabel("LOGIN PAGE");
            lblNewLabel_1.setForeground(Color.WHITE);
            lblNewLabel_1.setFont(new Font("Calibri", Font.BOLD, 16));
            add(lblNewLabel_1, gbc);

            gbc.gridwidth = 1;
            gbc.gridy++;
            JLabel lblNewLabel_2 = new JLabel("Username");
            lblNewLabel_2.setFont(new Font("Calibri", Font.BOLD, 14));
            lblNewLabel_2.setForeground(Color.WHITE);
            add(lblNewLabel_2, gbc);

            gbc.gridx++;
            txt_uname = new JTextField();
            txt_uname.setColumns(10);
            add(txt_uname, gbc);
            
            gbc.gridx = 0;
            gbc.gridy++;
            JLabel lblNewLabel_2_1 = new JLabel("Password");
            lblNewLabel_2_1.setForeground(Color.WHITE);
            lblNewLabel_2_1.setFont(new Font("Calibri", Font.BOLD, 14));
            add(lblNewLabel_2_1, gbc);

            gbc.gridx++;
            txt_pass = new JTextField();
            txt_pass.setColumns(10);
            add(txt_pass, gbc);

            gbc.gridwidth = 2;
            gbc.gridx = 0;
            gbc.gridy++;
            JButton btn_login = new JButton("Login");
            add(btn_login, gbc);
        }
        
        public String getUserName() {
            return txt_uname.getText().trim();
        }
        
        public String getPassword() {
            return txt_pass.getText().trim();
        }
        
    }
    
    public class Covid19Model {
        
        private boolean isAdmin;
        
        private String userName;
        private String password;
        
        public boolean isAdmin() {
            return isAdmin;
        }
        
        public void setAdmin(boolean isAdmin) {
            this.isAdmin = isAdmin;
        }
        
        public String getUserName() {
            return userName;
        }
        
        public void setUserName(String userName) {
            this.userName = userName;
        }
        
        public String getPassword() {
            return password;
        }
        
        public void setPassword(String password) {
            this.password = password;
        }
        
    }

}