如何阻止cardlayout .next（）和.previous（）循环

Question

我在这里有一个程序示例。我有3个面板，如果要插入面板，我想让用户停止按上一个按钮，最后一个面板panel_1也要停止panel_3。如果用户位于面板的开始或面板的末尾，有什么方法喜欢禁用按钮？

package cardlayoutalignment;

  import java.awt.*;
  import java.awt.event.ActionEvent;
  import java.awt.event.ActionListener;
  import javax.swing.*;
  import javax.swing.border.BevelBorder;
  import javax.swing.border.Border;
  import javax.swing.border.EmptyBorder;

public class gridbaglayoutdemo {
JFrame Card = new JFrame();

FlowLayout flow = new FlowLayout(FlowLayout.RIGHT,2,2);
Border etch = BorderFactory.createEtchedBorder(Color.white,Color.gray);
Border margin = new EmptyBorder(10,10,10,10);

public static GridBagLayout grid = new GridBagLayout();
GridBagConstraints c = new GridBagConstraints();
final static boolean shouldFill = true;

JPanel container = new JPanel();
JPanel divider = new JPanel();
JPanel bodypanel = new JPanel();
final JPanel buttonpanel = new JPanel();
JPanel panel_1 = new JPanel();
    JPanel panel_2 = new JPanel();
    JPanel panel_3 = new JPanel();
CardLayout cl = new CardLayout();

public gridbaglayoutdemo(){

    Card.setVisible(true);
    Card.setSize(605,333);
    Card.setTitle("");
    Card.setResizable(false);

    final Toolkit toolkit = Toolkit.getDefaultToolkit();
    Dimension dimension = Toolkit.getDefaultToolkit().getScreenSize();      
    int x=(int)((dimension.getWidth() - Card.getWidth())/2);
    int y=(int)((dimension.getHeight() - Card.getHeight())/2);

    Card.setLocation(x, y);
    Card.setDefaultCloseOperation(JFrame.DISPOSE_ON_CLOSE);


    bodypanel.setLayout(new BorderLayout());

    divider.setLayout(new BorderLayout());

    container.setLayout(cl);
    cl.show(container, "1");

    panel_1.setLayout(grid);

    JLabel label_1 = new JLabel("Enter 1:");
    label_1.setFont(new Font("Arial", Font.PLAIN, 18));
    c.fill = GridBagConstraints.HORIZONTAL;
    c.weightx = 0.5;
    c.weighty = 0;
    c.gridx = 0;
    c.gridy = 0;
    c.insets = new Insets(10,10,0,0);
    panel_1.add(label_1, c);

    JComboBox box_1 = new JComboBox();
    box_1.setPreferredSize(new Dimension(200,30));
    c.fill = GridBagConstraints.HORIZONTAL;
    c.weightx = 0.5;
    c.weighty = 0;
    c.gridx = 0;
    c.gridy = 1;
    c.insets = new Insets(10,10,0,0);
    panel_1.add(box_1,c);

    JLabel label = new JLabel("");
    label.setFont(new Font("Arial", Font.PLAIN, 18));
    c.fill = GridBagConstraints.HORIZONTAL;
    c.weightx = 0.5;
    c.weighty = 1;
    c.gridx = 0;
    c.gridy = 2;
    c.insets = new Insets(10,0,0,0);
    panel_1.add(label, c);


    panel_2.setLayout(grid);

    JLabel label_2 = new JLabel("Enter 2:");
    label_2.setFont(new Font("Arial", Font.PLAIN, 18));
    c.fill = GridBagConstraints.HORIZONTAL;
    c.weightx = 0.5;
    c.weighty = 0;
    c.gridx = 0;
    c.gridy = 0;
    c.insets = new Insets(10,10,0,0);
    panel_2.add(label_2,c);

    JTextField text_2 = new JTextField();
    text_2.setPreferredSize(new Dimension(200,30));
    c.fill = GridBagConstraints.HORIZONTAL;
    c.weightx = 0.5;
    c.weighty = 0;
    c.gridx = 0;
    c.gridy = 1;
    c.insets = new Insets(10,10,0,0);
    panel_2.add(text_2,c);

    JLabel label_22 = new JLabel("");
    label_22.setFont(new Font("Arial", Font.PLAIN, 18));
    c.fill = GridBagConstraints.HORIZONTAL;
    c.weightx = 0.5;
    c.weighty = 1;
    c.gridx = 0;
    c.gridy = 2;
    c.insets = new Insets(10,0,0,0);
    panel_2.add(label_22, c);


    panel_3.setLayout(grid);

    JLabel label_3 = new JLabel("Enter 3:");
    label_3.setFont(new Font("Arial", Font.PLAIN, 18));
    c.fill = GridBagConstraints.HORIZONTAL;
    c.weightx = 0.5;
    c.weighty = 0;
    c.gridx = 0;
    c.gridy = 0;
    c.insets = new Insets(10,10,0,0);
    panel_3.add(label_3,c);

    JTextField text_3 = new JTextField();
    text_3.setPreferredSize(new Dimension(200,30));
    c.fill = GridBagConstraints.HORIZONTAL;
    c.weightx = 0.5;
    c.weighty = 0;
    c.gridx = 0;
    c.gridy = 1;
    c.insets = new Insets(10,10,0,0);
    panel_3.add(text_3,c);

    JLabel label_33 = new JLabel("");
    label_33.setFont(new Font("Arial", Font.PLAIN, 18));
    c.fill = GridBagConstraints.HORIZONTAL;
    c.weightx = 0.5;
    c.weighty = 1;
    c.gridx = 0;
    c.gridy = 2;
    c.insets = new Insets(10,0,0,0);
    panel_3.add(label_33, c);

    buttonpanel.setLayout(new FlowLayout(SwingConstants.RIGHT));
    buttonpanel.setBorder(new EmptyBorder(0,10,0,0));

    JButton btnBack = new JButton("< Back");
    btnBack.addActionListener(new ActionListener() {
        public void actionPerformed(ActionEvent e) {

        cl.previous(container);
        buttonpanel.repaint();
        }   
    });
    btnBack.setFont(new Font("Arial", Font.PLAIN, 20));
    btnBack.setFocusable(false);
    btnBack.setFocusTraversalKeysEnabled(false);
    btnBack.setFocusPainted(false);
    btnBack.setBorder(new BevelBorder(BevelBorder.RAISED, Color.BLACK, null, null, null));
    btnBack.setPreferredSize(new Dimension(110, 40));
    btnBack.setBackground(new Color(224,223,227));
    buttonpanel.add(btnBack);

    JButton btnNext = new JButton("Next >");
    btnNext.addActionListener(new ActionListener() {
        public void actionPerformed(ActionEvent e) {
            cl.next(container);
            buttonpanel.repaint();
        }   
    });
    btnNext.setFont(new Font("Arial", Font.PLAIN, 20));
    btnNext.setFocusable(false);
    btnNext.setFocusTraversalKeysEnabled(false);
    btnNext.setFocusPainted(false);
    btnNext.setBorder(new BevelBorder(BevelBorder.RAISED, Color.BLACK, null, null, null));
    btnNext.setPreferredSize(new Dimension(110, 40));
    btnNext.setBackground(new Color(224,223,227));
    buttonpanel.add(btnNext);

    final JButton btnCancel = new JButton("Cancel");
    btnCancel.addActionListener(new ActionListener() {
        public void actionPerformed(ActionEvent e) {
            Window dialog = SwingUtilities.windowForComponent( btnCancel );
            dialog.dispose(); 
        }   
    });
    btnCancel.setFont(new Font("Arial", Font.PLAIN, 20));
    btnCancel.setFocusable(false);
    btnCancel.setFocusTraversalKeysEnabled(false);
    btnCancel.setFocusPainted(false);
    btnCancel.setBorder(new BevelBorder(BevelBorder.RAISED, Color.BLACK, null, null, null));
    btnCancel.setPreferredSize(new Dimension(110, 40));
    btnCancel.setBackground(new Color(224,223,227));
    buttonpanel.add(btnCancel);

    JPanel numberpanel = new JPanel();
    numberpanel.setPreferredSize(new Dimension(221,0));
    numberpanel.setBorder(new EmptyBorder(10,0,0,10));
    numberpanel.setBorder(BorderFactory.createEtchedBorder(Color.white,Color.gray));
    numberpanel.setLayout(flow);

    JButton button_7 = new JButton("7");
    button_7.addActionListener(new ActionListener() {
        public void actionPerformed(ActionEvent e) {

        }   
    });
    button_7.setFont(new Font("Arial", Font.PLAIN, 30));
    button_7.setFocusable(false);
    button_7.setFocusTraversalKeysEnabled(false);
    button_7.setFocusPainted(false);
    button_7.setBorder(new BevelBorder(BevelBorder.RAISED, Color.BLACK, null, null, null));
    button_7.setPreferredSize(new Dimension(70, 70));
    button_7.setBackground(new Color(224,223,227));
    numberpanel.add(button_7);

    JButton button_8 = new JButton("8");
    button_8.addActionListener(new ActionListener() {
        public void actionPerformed(ActionEvent e) {

        }   
    });
    button_8.setFont(new Font("Arial", Font.PLAIN, 30));
    button_8.setFocusable(false);
    button_8.setFocusTraversalKeysEnabled(false);
    button_8.setFocusPainted(false);
    button_8.setBorder(new BevelBorder(BevelBorder.RAISED, Color.BLACK, null, null, null));
    button_8.setPreferredSize(new Dimension(70, 70));
    button_8.setBackground(new Color(224,223,227));
    numberpanel.add(button_8);

    JButton button_9 = new JButton("9");
    button_9.addActionListener(new ActionListener() {
        public void actionPerformed(ActionEvent e) {

        }   
    });
    button_9.setFont(new Font("Arial", Font.PLAIN, 30));
    button_9.setFocusable(false);
    button_9.setFocusTraversalKeysEnabled(false);
    button_9.setFocusPainted(false);
    button_9.setBorder(new BevelBorder(BevelBorder.RAISED, Color.BLACK, null, null, null));
    button_9.setPreferredSize(new Dimension(70, 70));
    button_9.setBackground(new Color(224,223,227));
    numberpanel.add(button_9);



    Card.add(bodypanel);
        bodypanel.add(divider, BorderLayout.WEST);
            divider.add(container, BorderLayout.NORTH);     
                container.add(panel_1, "1");
                container.add(panel_2, "2");
                container.add(panel_3, "3");
                //container.add(panel_4, "4");
                //container.add(p5.panel_5, "5");
                //container.add(p6.panel_6, "6");
            divider.add(buttonpanel, BorderLayout.SOUTH);
        bodypanel.add(numberpanel, BorderLayout.EAST);
  }

   public static void main(String[] args){
     //Use the event dispatch thread for Swing components
     EventQueue.invokeLater(new Runnable()
     {
    @Override
     public void run()
     {
     new gridbaglayoutdemo();         
     }
     });

     }
 }

抱歉，工作代码不够短。我已经修剪了一些。那是我能做的最短的版本。

Answer 1

“如果用户是在面板的开始或面板的末尾，有没有办法喜欢禁用按钮？”

根据如何使用CardLayout和CardLayout
API
，没有直接的方法可以做到这一点。

但是您可以轻松实现此功能，使int变量与当前卡号保持一致，并再次检查其值ts 0（对于第一张卡）或容器的组件数（对于最后一张卡）。例如：

public class GridBagLayoutDemo { // note code convention!

    int currentCard = 0;
    Action backAction, nextAction;
    ...

    public GridBagLayoutDemo() {
        ...
        backAction = new AbstractAction("< Back") {
            @Override
            public void actionPerformed(ActionEvent e) {
                currentCard--;
                GridBagLayoutDemo.this.evaluateActions();
            }
        };

        nextAction = new AbstractAction("Next >") {
            @Override
            public void actionPerformed(ActionEvent e) {
                currentCard++;
                GridBagLayoutDemo.this.evaluateActions();
            }
        };

        JButton btnBack = new JButton(backAction);
        ...
        JButton btnNext = new JButton(nextAction);
        ...
    }

    private void evaluateActions() {
        backAction.setEnabled(currentCard > 0);
        nextAction.setEnabled(currentCard < container.getComponentCount() - 1);
    }
    ...
}

附录

仔细研究CardLayout实现，默认情况下实现此功能真的很容易（除非我遗漏了一些东西）：

public class CardLayout implements LayoutManager2,
                                   Serializable {

    /*
     * This creates a Vector to store associated
     * pairs of components and their names.
     * @see java.util.Vector
     */
    Vector vector = new Vector();

    /*
     * Index of Component currently displayed by CardLayout.
     */
    int currentCard = 0;

    ...

    /* 
     * Hypothetical implementations
     */

    public boolean isDisplayingFirstCard() {
        return currentCard == 0;
    }

    public boolean isDisplayingLastCard() {
        return currentCard == vector.size() - 1;
    }
}

不知道为什么他们没有提供这种有用的功能。