Question

so I have this jFrame with a Panel.
Inside that panel there are two more panels and the layout is set to cards.
Inside one of those two panels there is a button.
How can I change the panel thats being displayed when that button is pressed?

Answer 1

Try this code snippet, hope the comments might help you understand the sequence.

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

/* Here we are first declaring our class that will act as the
 * base for other panels or in other terms the base for CardLayout.
 */

public class CardLayoutTest
{
    private static final String CARD_JBUTTON =  "Card JButton";
    private static final String CARD_JTEXTFIELD = "Card JTextField";    
    private static final String CARD_JRADIOBUTTON = "Card JRadioButton";

    private static void createAndShowGUI()
    {
        JFrame frame = new JFrame("Card Layout Test");
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        frame.setLocationRelativeTo(null);

        // This JPanel is the base for CardLayout for other JPanels.
        final JPanel contentPane = new JPanel();
        contentPane.setLayout(new CardLayout(20, 20));

        /* Here we be making objects of the Window Series classes
         * so that, each one of them can be added to the JPanel 
         * having CardLayout. 
         */
        Window1 win1 = new Window1();
        contentPane.add(win1, CARD_JBUTTON);
        Window2 win2 = new Window2();
        contentPane.add(win2, CARD_JTEXTFIELD);
        Window3 win3 = new Window3();
        contentPane.add(win3, CARD_JRADIOBUTTON);

        /* We need two JButtons to go to the next Card
         * or come back to the previous Card, as and when
         * desired by the User.
         */
        JPanel buttonPanel = new JPanel(); 
        final JButton previousButton = new JButton("PREVIOUS");
        previousButton.setBackground(Color.BLACK);
        previousButton.setForeground(Color.WHITE);
        final JButton nextButton = new JButton("NEXT");
        nextButton.setBackground(Color.RED);
        nextButton.setForeground(Color.WHITE);
        buttonPanel.add(previousButton);
        buttonPanel.add(nextButton);

        /* Adding the ActionListeners to the JButton,
         * so that the user can see the next Card or
         * come back to the previous Card, as desired.
         */
        previousButton.addActionListener(new ActionListener()
        {
            public void actionPerformed(ActionEvent ae)
            {
                CardLayout cardLayout = (CardLayout) contentPane.getLayout();
                cardLayout.previous(contentPane);
            }
        });
        nextButton.addActionListener(new ActionListener()
        {
            public void actionPerformed(ActionEvent ae)
            {
                CardLayout cardLayout = (CardLayout) contentPane.getLayout();
                cardLayout.next(contentPane);   
            }
        });

        // Adding the contentPane (JPanel) and buttonPanel to JFrame.
        frame.add(contentPane, BorderLayout.CENTER);
        frame.add(buttonPanel, BorderLayout.PAGE_END);

        frame.pack();
        frame.setVisible(true);
    }

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

class Window1 extends JPanel
{
    /*
     * Here this is our first Card of CardLayout, which will
     * be added to the contentPane object of JPanel, which
     * has the LayoutManager set to CardLayout.
     * This card consists of Two JButtons.
     */  
    private ActionListener action;

    public Window1() 
    {
        init();
    }

    private void init() 
    {
        final JButton clickButton = new JButton("CLICK ME");
        final JButton dontClickButton = new JButton("DON\'T CLICK ME");     

        action = new ActionListener()
        {
            public void actionPerformed(ActionEvent ae)
            {
                if (ae.getSource() == clickButton)
                {
                    JOptionPane.showMessageDialog(null, "Hello there dude!"
                                                , "Right Button", JOptionPane.INFORMATION_MESSAGE);
                }
                else if (ae.getSource() == dontClickButton)
                {
                    JOptionPane.showMessageDialog(null, "I told you not to click me!"
                                                        , "Wrong Button", JOptionPane.PLAIN_MESSAGE);
                }
            }
        };

        clickButton.addActionListener(action);
        dontClickButton.addActionListener(action);

        add(clickButton);
        add(dontClickButton);
    }
}

class Window2 extends JPanel implements ActionListener 
{
    /*
     * Here this is our second Card of CardLayout, which will
     * be added to the contentPane object of JPanel, which
     * has the LayoutManager set to CardLayout.
     * This card consists of a JLabel and a  JTextField
     * with GridLayout.
     */  

    private JTextField textField;

    public Window2() 
    {
        init();
    }

    private void init() 
    {
        setLayout(new GridLayout(1, 2));
        JLabel userLabel = new JLabel("Your Name : ");
        textField = new JTextField();
        textField.addActionListener(this);

        add(userLabel);
        add(textField);
    }

    public void actionPerformed(ActionEvent e) 
    {            
        if (textField.getDocument().getLength() > 0)
            JOptionPane.showMessageDialog(null, "Your Name is : " + textField.getText()
                                                                            , "User\'s Name : ", JOptionPane.QUESTION_MESSAGE);
    }
}

class Window3 extends JPanel
{
    /*
     * Here this is our third Card of CardLayout, which will
     * be added to the contentPane object of JPanel, which
     * has the LayoutManager set to CardLayout.
     * This card consists of Two JLabels and two JCheckBox
     * with GridLayout.
     */  
    private ActionListener state;

    public Window3()
    {
        init();
    }

    public void init()
    {
        setLayout(new GridLayout(2, 2));
        JLabel maleLabel = new JLabel("MALE", JLabel.CENTER);
        final JCheckBox maleBox = new JCheckBox();
        JLabel femaleLabel = new JLabel("FEMALE", JLabel.CENTER);
        final JCheckBox femaleBox = new JCheckBox();

        state = new ActionListener()
        {
            public void actionPerformed(ActionEvent ae)
            {
                if (maleBox == (JCheckBox) ae.getSource())
                {
                    femaleBox.setSelected(false);
                    JOptionPane.showMessageDialog(null, "Congrats you are a Male"
                                                , "Gender : ", JOptionPane.INFORMATION_MESSAGE);                            
                }
                else if (femaleBox == (JCheckBox) ae.getSource())
                {
                    maleBox.setSelected(false);
                    JOptionPane.showMessageDialog(null, "Congrats you are a Female"
                                            , "Gender : ", JOptionPane.INFORMATION_MESSAGE);                        
                }
            }
        };

        maleBox.addActionListener(state);
        femaleBox.addActionListener(state);
        add(maleLabel);
        add(maleBox);
        add(femaleLabel);
        add(femaleBox);
    }
}