如何将 CardLayout 与多个 JButton 一起使用？

Question

I need to make a GUI that asks the users for details and then save them in a linked list. I wanted to use the CardLayout to switch from one frame to another, which is something I'm doing for the first time. I have done probably less half of what I need to do and here I am quite lost in this part. The code below compiles and executes but when I click the buttons, the desired change does not happen . What could be wrong?

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

public class MyDatabaseWindow extends JPanel{
public static final String FRONT_PAGE = "Front Page";
public static final String BROWSE_MEMORIES = "Browse Memories";
public static final String ADD_EDIT = "Add Edit";
public static final String VIEW_MEMORY = "View Memory";

public static void createAndShowGUI() {
    final MyDatabaseWindow mdbw = new MyDatabaseWindow();

    JPanel buttonPanel = new JPanel();
    buttonPanel.setLayout(null);
    final JButton addButton = new JButton("Add");
    final JButton editButton = new JButton("Edit");
    final JButton deleteButton = new JButton("Delete");
    final JButton browseButton = new JButton("Browse");
    final JButton searchButton = new JButton("Search");

    addButton.setBounds(100, 400, 100, 100);
    editButton.setBounds(200, 400, 100, 100);
    deleteButton.setBounds(300, 400, 100, 100);
    browseButton.setBounds(400, 400, 100, 100);
    searchButton.setBounds(500, 400, 100, 100);

    buttonPanel.add(addButton);
    buttonPanel.add(editButton);
    buttonPanel.add(deleteButton);
    buttonPanel.add(browseButton);
    buttonPanel.add(searchButton);

    addButton.addActionListener(new ActionListener() {
        public void actionPerformed(ActionEvent ae) {
            mdbw.goToAddPage();
        }
    });
    editButton.addActionListener(new ActionListener() {
        public void actionPerformed(ActionEvent ae) {
            mdbw.goToBrowse();
        }
    });
    deleteButton.addActionListener(new ActionListener() {
        public void actionPerformed(ActionEvent ae) {
            mdbw.goToBrowse();
        }
    });
    browseButton.addActionListener(new ActionListener() {
        public void actionPerformed(ActionEvent ae) {
            mdbw.goToBrowse();
        }
    });
    searchButton.addActionListener(new ActionListener() {
        public void actionPerformed(ActionEvent ae) {
            mdbw.goToSearch();
        }
    });

    JFrame frame = new JFrame("Memory Files");
    frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
    frame.setSize(700, 540);
    frame.setLocation(250, 100);
    frame.getContentPane().add(mdbw);
    frame.getContentPane().add(buttonPanel);
    frame.setVisible(true);
}

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

private CardLayout cardLayout = new CardLayout();
private JPanel cardShowingPanel = new JPanel(cardLayout);

public MyDatabaseWindow() {
    Window1 win1 = new Window1();
    cardShowingPanel.add(win1, FRONT_PAGE);
    Window2 win2 = new Window2();
    cardShowingPanel.add(win2, BROWSE_MEMORIES);
    Window3 win3 = new Window3();
    cardShowingPanel.add(win3, ADD_EDIT);
    Window4 win4 = new Window4();
    cardShowingPanel.add(win4, VIEW_MEMORY);

    setLayout(new BorderLayout());
    add(cardShowingPanel, BorderLayout.NORTH);
}

public void goToAddPage() {
    cardLayout.first(cardShowingPanel);
}
public void goToBrowse() {
    cardLayout.first(cardShowingPanel);
    cardLayout.next(cardShowingPanel);
}
public void goToSearch() {
    cardLayout.last(cardShowingPanel);
}
public void showCard(String key) {
    cardLayout.show(cardShowingPanel, key);
}
}

class Window1 extends JPanel {
public Window1() {
    init();
}

private void init() { //dummy details
    JLabel title = new JLabel("Memory Files");
    title.setBounds(0, 0, 500, 500);
    add(title);
}
}
class Window2 extends JPanel {

public Window2() {
    init();
}
private void init() { //dummy details
    JLabel title = new JLabel("Memory Files");
    title.setBounds(0, 0, 500, 500);
    add(title);
}
}
class Window3 extends JPanel {

public Window3() {
    init();
}
private void init() {//dummy details
    JLabel title = new JLabel("Memory Files");
    title.setBounds(0, 0, 500, 500);
    add(title);
}
}
class Window4 extends JPanel {

    public Window4() {
        init();
    }
    private void init() {//dummy details
        JLabel title = new JLabel("Memory Files");
        title.setBounds(0, 0, 500, 500);
        add(title);
    }
}

Answer 1

The main problem is the use of null-layouts and these lines of code:

frame.getContentPane().add(mdbw);
frame.getContentPane().add(buttonPanel);

First you add the panel using the CardLayout to BorderLayout.CENTER , then you "overlay" it with your buttonPanel , which is using null-layout.

I would go with a simple FlowLayout (the default layout-manager for a JPanel ) for the buttonPanel and add it to the BorderLayout.SOUTH of the contentPane . I would also strongly recommend reading this tutorial .

So remove the following lines of code:

buttonPanel.setLayout(null);
...
addButton.setBounds(100, 400, 100, 100);
editButton.setBounds(200, 400, 100, 100);
deleteButton.setBounds(300, 400, 100, 100);
browseButton.setBounds(400, 400, 100, 100);
searchButton.setBounds(500, 400, 100, 100);

and change frame.getContentPane().add(buttonPanel); to frame.getContentPane().add(buttonPanel, BorderLayout.SOUTH); .

Also forget about the null-layout / setBounds() in your Window -classes.

(Note that you still won't see the text change if you press a button because you always add a JLabel with the same text ("Memory Files") to your Windows .)