无法使CardLayout /按钮ActionListeners正常工作

Question

I know it's something to do with how I've set it up and the actionlistener not being correctly set to the frame or something but I just can't get my hear around it. If someone could point me in the right direction I'd be much obliged. Sorry for noob question.

Here's what I have:

import java.awt.*;
import java.awt.event.*;
import javax.swing.*;

public class Main implements ActionListener {

    JPanel cardHolder;
    public static final String HOME_CARD = "Home";
    public static final String BLUE_PANEL = "Blue Panel";
    public static final String RED_PANEL = "Red Panel";
    public static final String ORANGE_PANEL = "Orange Panel";

    public static JButton home = new JButton("Home");
    public static JButton bluePanel = new JButton("Blue Card");
    public static JButton redPanel = new JButton("Red Panel");
    public static JButton orangePanel = new JButton("Orange Panel");

    public static JPanel createCardHolderPanel() {
        JPanel cardHolder = new JPanel(new CardLayout());
        cardHolder.setBorder(BorderFactory.createTitledBorder("Card Holder Panel"));

        cardHolder.add(createHomeCard(), HOME_CARD);
        cardHolder.add(createBluePanel(), BLUE_PANEL);
        cardHolder.add(createRedPanel(), RED_PANEL);
        cardHolder.add(createOrangePanel(), ORANGE_PANEL);

        return cardHolder;
    }

    private static JPanel createOrangePanel() {
        JPanel orangePanel = new JPanel();

        orangePanel.setBackground(Color.orange);
        return orangePanel;
    }

    private static Component createRedPanel() {
        JPanel redPanel = new JPanel();

        redPanel.setBackground(Color.red);
        return redPanel;
    }

    private static Component createBluePanel() {
        JPanel bluePanel = new JPanel();

        bluePanel.setBackground(Color.blue);
        return bluePanel;
    }

    private static Component createHomeCard() {
        JPanel homePanel = new JPanel();

        homePanel.setBackground(Color.GRAY);
        return homePanel;
    }

    public static JPanel createButtonPanel() {
        JPanel buttonPanel = new JPanel(new GridLayout(4, 0, 5, 5));
        buttonPanel.setBorder(BorderFactory.createTitledBorder("Button Panel"));

        buttonPanel.add(home);
        buttonPanel.add(bluePanel);
        buttonPanel.add(redPanel);
        buttonPanel.add(orangePanel);

        return buttonPanel;
    }

    public static JPanel createContentPane() {
        JPanel contentPane = new JPanel(new BorderLayout());

        contentPane.setBorder(BorderFactory.createTitledBorder("Main Content Pane"));
        contentPane.setBackground(Color.WHITE);
        contentPane.setPreferredSize(new Dimension(499, 288));

        contentPane.add(createButtonPanel(), BorderLayout.WEST);
        contentPane.add(createCardHolderPanel(),BorderLayout.CENTER);

        return contentPane;
    }

    public static JMenuBar createMenuBar() {
        JMenuBar menuBar = new JMenuBar();

        JMenu file = new JMenu("File");
        JMenu users = new JMenu("Users");
        JMenu options = new JMenu("Options");
        JMenu help = new JMenu("Help");

        menuBar.add(file);
        menuBar.add(users);
        menuBar.add(options);
        menuBar.add(help);

        return menuBar;
    }

    public static void createAndShowGUI() {
        JFrame frame = new JFrame("Simple CardLayout Program");
        frame.setContentPane(createContentPane());
        frame.setJMenuBar(createMenuBar());
        frame.pack();
        frame.setVisible(true);
    }

    public static void main(String[] args) {
        SwingUtilities.invokeLater(new Runnable() {
            public void run() {
                createAndShowGUI();
            }
        });
    }

    @Override
    public void actionPerformed(ActionEvent e) {

        if (e.getSource() == home) {
            CardLayout cardLayout = (CardLayout) (cardHolder.getLayout());
            cardLayout.show(cardHolder, HOME_CARD);
        }

        if (e.getSource() == bluePanel) {
            CardLayout cardLayout = (CardLayout) (cardHolder.getLayout());
            cardLayout.show(cardHolder, BLUE_PANEL);
        }

        if (e.getSource() == redPanel) {
            CardLayout cardLayout = (CardLayout) (cardHolder.getLayout());
            cardLayout.show(cardHolder, RED_PANEL);
        }

        if (e.getSource() == orangePanel) {
            CardLayout cardLayout = (CardLayout) (cardHolder.getLayout());
            cardLayout.show(cardHolder, ORANGE_PANEL);
        }
    }
}

Answer 1

Others have suggested listening to the buttons; in addition:

• Prefer the lowest accessibility consistent with use, eg private rather than public .
• Don't make everything static .
• Use static for immutable constants used throughout the class.
• Use class variables rather than static members for content.
• Don't repeat your self, eg initialize cardLayout just once in your actionPerformed)() .

• Use parameters rather than separate methods for each color, eg

   private JPanel createColorPanel(Color color) {...} 

Revised code:

import java.awt.*;
import java.awt.event.*;
import javax.swing.*;

public class Main implements ActionListener {

    private static final String HOME_CARD = "Home";
    private static final String BLUE_PANEL = "Blue Panel";
    private static final String RED_PANEL = "Red Panel";
    private static final String ORANGE_PANEL = "Orange Panel";
    private JPanel cardHolder;
    private JButton homeButton = new JButton("Home");
    private JButton blueButton = new JButton("Blue Card");
    private JButton redButton = new JButton("Red Panel");
    private JButton orangeButton = new JButton("Orange Panel");

    public JPanel createCardHolderPanel() {
        cardHolder = new JPanel(new CardLayout());
        cardHolder.setBorder(BorderFactory.createTitledBorder("Card Holder Panel"));
        cardHolder.add(createColorPanel(Color.gray), HOME_CARD);
        cardHolder.add(createColorPanel(Color.blue), BLUE_PANEL);
        cardHolder.add(createColorPanel(Color.red), RED_PANEL);
        cardHolder.add(createColorPanel(Color.orange), ORANGE_PANEL);

        return cardHolder;
    }

    private JPanel createColorPanel(Color color) {
        JPanel panel = new JPanel();
        panel.setBackground(color);
        return panel;
    }

    public JPanel createButtonPanel() {
        JPanel buttonPanel = new JPanel(new GridLayout(4, 0, 5, 5));
        buttonPanel.setBorder(BorderFactory.createTitledBorder("Button Panel"));
        buttonPanel.add(homeButton);
        buttonPanel.add(blueButton);
        buttonPanel.add(redButton);
        buttonPanel.add(orangeButton);
        homeButton.addActionListener(this);
        blueButton.addActionListener(this);
        redButton.addActionListener(this);
        orangeButton.addActionListener(this);
        return buttonPanel;
    }

    public JPanel createContentPane() {
        JPanel panel = new JPanel(new BorderLayout());
        panel.setBorder(BorderFactory.createTitledBorder("Main Content Pane"));
        panel.setBackground(Color.WHITE);
        panel.setPreferredSize(new Dimension(499, 288));
        panel.add(createButtonPanel(), BorderLayout.WEST);
        panel.add(createCardHolderPanel(), BorderLayout.CENTER);
        return panel;
    }

    public JMenuBar createMenuBar() {
        JMenuBar menuBar = new JMenuBar();
        JMenu file = new JMenu("File");
        JMenu users = new JMenu("Users");
        JMenu options = new JMenu("Options");
        JMenu help = new JMenu("Help");
        menuBar.add(file);
        menuBar.add(users);
        menuBar.add(options);
        menuBar.add(help);
        return menuBar;
    }

    @Override
    public void actionPerformed(ActionEvent e) {
        CardLayout cardLayout = (CardLayout) (cardHolder.getLayout());
        if (e.getSource() == homeButton) {
            cardLayout.show(cardHolder, HOME_CARD);
        }
        if (e.getSource() == blueButton) {
            cardLayout.show(cardHolder, BLUE_PANEL);
        }
        if (e.getSource() == redButton) {
            cardLayout.show(cardHolder, RED_PANEL);
        }
        if (e.getSource() == orangeButton) {
            cardLayout.show(cardHolder, ORANGE_PANEL);
        }
    }

    public static void createAndShowGUI() {
        JFrame frame = new JFrame("Simple CardLayout Program");
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        Main main = new Main();
        frame.setJMenuBar(main.createMenuBar());
        frame.add(main.createContentPane());
        frame.pack();
        frame.setVisible(true);
    }

    public static void main(String[] args) {
        SwingUtilities.invokeLater(new Runnable() {

            @Override
            public void run() {
                createAndShowGUI();
            }
        });
    }
}

Answer 2

You have not set an action listener for any of the buttons. Implementing the actionPerformed method of the interface does not automatically set an action listener for the buttons. You have to call the addActionListener method which in your case would look like the following since your class implements the ActionListener Interface.

public static JButton home = new JButton("Home").addActionListener(this); 
public static JButton bluePanel = new JButton("Blue Card").addActionListener(this); 
public static JButton redPanel = new JButton("Red Panel").addActionListener(this); 
public static JButton orangePanel = new JButton("Orange Panel").addActionListener(this);