Multiple jpanels in a jframe

Question

I am currently trying to make a little app using a jframe that has multiple jpanels. I have a couple questions about this.

1. There has to be a cleaner way of making an app with 16 different panels than having it all inside one class. What are some other options.

2. Currently I only have 3 panels. I haven't gone any further because 2 of the panels aren't reflecting my changes. They are the two panels I call using

    removeAll();
    add();
    revalidate();
    repaint(); 

What would be causing the other panels I am calling to be blank?

Here is a look at what I have, any advice would be great. Thanks

public class Jframetest extends JFrame {

    private JPanel Home;
    private JPanel masslog;
    private JPanel DEH;

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

    public Jframetest() {
        setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        setResizable(false);
        setBounds(100, 100, 618, 373);
        Home = new JPanel();
        masslog = new JPanel();
        DEH = new JPanel();

        Home.setBackground(new Color(255, 250, 250));
        Home.setBorder(new LineBorder(Color.DARK_GRAY, 1, true));
        DEH.setBackground(new Color(255, 250, 250));
        DEH.setBorder(new LineBorder(Color.DARK_GRAY, 1, true));
        masslog.setBackground(new Color(255, 250, 250));
        masslog.setBorder(new LineBorder(Color.DARK_GRAY, 1, true));
        setContentPane(Home);
        Home.setLayout(null);

        JButton dehbutton = new JButton("Sign in");
        dehbutton.setFont(new Font("Tahoma", Font.PLAIN, 14));
        dehbutton.setForeground(new Color(0, 0, 0));
        dehbutton.setBackground(UIManager.getColor("Menu.selectionBackground"));
        DEH.add(dehbutton);

        JButton btnNewButton = new JButton("Data Entry login");
        btnNewButton.setFont(new Font("Tahoma", Font.PLAIN, 14));
        btnNewButton.setForeground(new Color(0, 0, 0));
        btnNewButton.setBackground(UIManager.getColor("Menu.selectionBackground"));

        btnNewButton.addActionListener(new ActionListener() {
            public void actionPerformed(ActionEvent arg0) {
                Home.removeAll();
                Home.add(DEH);
                Home.revalidate();
                Home.repaint();

                // JOptionPane.showMessageDialog(null, "Username/Password incorrect");
            }
        });
        btnNewButton.setBounds(44, 214, 204, 61);
        Home.add(btnNewButton);

        final JButton button = new JButton("Manager and Associate login");
        button.setFont(new Font("Tahoma", Font.PLAIN, 14));
        button.setBackground(UIManager.getColor("EditorPane.selectionBackground"));
        button.addActionListener(new ActionListener() {
            public void actionPerformed(ActionEvent e) {
                Home.removeAll();
                Home.add(masslog);
                Home.revalidate();
                Home.repaint();

            }
        });
        button.setBounds(340, 214, 204, 61);
        Home.add(button);

        JTextPane txtpnEmployeeLogin = new JTextPane();
        txtpnEmployeeLogin.setForeground(Color.DARK_GRAY);
        txtpnEmployeeLogin.setBackground(Color.WHITE);
        txtpnEmployeeLogin.setFont(new Font("Tahoma", Font.PLAIN, 34));
        txtpnEmployeeLogin.setText("Employee Login");
        txtpnEmployeeLogin.setBounds(181, 123, 260, 52);
        Home.add(txtpnEmployeeLogin);

        JLabel lblNewLabel = new JLabel("New label");
        lblNewLabel.setIcon(new ImageIcon("C:\\Users\\Will and April\\Downloads\\your-logo-here.jpg"));
        lblNewLabel.setBounds(427, 11, 165, 67);
        Home.add(lblNewLabel);

    }

}

Answer 1

Your mistake is using a null layout, revalidate, invalidate and validate will no longer have any significant meaning, because they are related to supporting the layout management API.

Because you've removed the layout manager, you panels no longer have anything to tell them what size or location that they should appear at, meaning when you add a new component, it has a size of 0x0 and position of 0x0

Update with example

There are many reasons why you should take advantage of the layout manager API, including automatic handling of differences between how fonts are rendered on different systems, dynamic and resizable layouts, differences in screen resolution and DPI to name a few.

It will also encourage you to separate your UI into areas of responsibility instead of trying to dump your entire UI code into a single class (yes, I've seen this done, yes, I've spent most of my career cleaning up after people who do this...)

This example makes use of CardLayout and GridBagLayout, but you should take the time to become farmiluar with the some of the others avaiable in the default JDK

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.JPanel;
import javax.swing.JTextField;
import javax.swing.border.EmptyBorder;

public class FrameTest extends JFrame {
    public static void main(String[] args) {
        EventQueue.invokeLater(new Runnable() {
            public void run() {
                try {
                    FrameTest frame = new FrameTest();
                    frame.setVisible(true);
                } catch (Exception e) {
                    e.printStackTrace();
                }
            }
        });
    }

    public FrameTest() {
        setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

        final CardLayout layout = new CardLayout();
        setLayout(layout);
        LoginPane loginPane = new LoginPane();
        add(loginPane, "login");
        add(new NewLoginPane(), "newLogin");
        add(new ManagerLoginPane(), "managerLogin");

        loginPane.addActionListener(new ActionListener() {
            @Override
            public void actionPerformed(ActionEvent e) {
                String command = e.getActionCommand();
                System.out.println(command);
                if ("new".equals(command)) {
                    layout.show(getContentPane(), "newLogin");
                } else if ("manager".equals(command)) {
                    layout.show(getContentPane(), "managerLogin");
                }
            }
        });

        layout.show(getContentPane(), "layout");

        pack();
        setLocationRelativeTo(null);
    }

    public class LoginPane extends JPanel {

        private JTextField userName;
        private JButton newButton;
        private JButton managerButton;

        public LoginPane() {
            setBorder(new EmptyBorder(20, 20, 20, 20));
            setLayout(new GridBagLayout());
            GridBagConstraints gbc = new GridBagConstraints();
            gbc.gridx = 0;
            gbc.gridy = 0;
            gbc.gridwidth = 2;
            gbc.weightx = 1;
            gbc.insets = new Insets(10, 10, 10, 10);

            userName = new JTextField(10);
            userName.setFont(new Font("Tahoma", Font.PLAIN, 34));
            add(userName, gbc);

            gbc.gridx = 0;
            gbc.gridy = 1;
            gbc.gridwidth = 1;
            gbc.weightx = 0;
            gbc.fill = GridBagConstraints.HORIZONTAL;

            newButton = new JButton("Sign in");
            newButton.setActionCommand("new");
            managerButton = new JButton("Manager and Associate login");
            managerButton.setActionCommand("manager");

            add(newButton, gbc);
            gbc.gridx++;
            add(managerButton, gbc);                
        }

        public void addActionListener(ActionListener listener) {
            newButton.addActionListener(listener);
            managerButton.addActionListener(listener);
        }

        public void remveActionListener(ActionListener listener) {
            newButton.removeActionListener(listener);
            managerButton.removeActionListener(listener);
        }

        public String getUserName() {               
            return userName.getText();                
        }            
    }

    public class NewLoginPane extends JPanel {
        public NewLoginPane() {
            setLayout(new GridBagLayout());
            add(new JLabel("New Login"));
        }           
    }

    public class ManagerLoginPane extends JPanel {
        public ManagerLoginPane() {
            setLayout(new GridBagLayout());
            add(new JLabel("Welcome overlord"));
        }           
    }
}