java - CardLayout 从另一个类更改面板

Question

我正在自学 java GUI，在浏览了 stackoverflow 上的一些示例后，我陷入了这个问题(如下)。我想知道的是如何从另一个类转到上一个 JPanel？

如果我在 Window3 中有一个带有 Action 监听器的 JButton，我如何告诉它转到上一个类？

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);
    }
}

Answer 1

将 CardLayout 和 CardLayout-using JPanel 设置为 CardLayout-using 类的私有(private)字段，例如名为 cardLayout 和 cardShowingPanel，并为该类提供两个公共(public)方法:

public void nextCard() {
   // in here call next() on the CardLayout
   cardLayout.next(cardShowingPanel);
}

和

public void previousCard() {
   // in here call previous() on the CardLayout
   cardLayout.previous(cardShowingPanel);
}

为了获得最大的灵 active ，还可以考虑创建一个 showCard(...) 方法来镜像 CardLayout 的 show(...) 方法:

public void showCard(String key) {
   cardLayout.show(cardShowingPanel, key);
}

完成此操作后，我使用公共(public)常量作为键来将组件添加到卡片显示 JPanel，以便外部类在想要显示特定卡片时可以重用这些常量。

然后任何持有此类引用的类都可以调用公共(public)方法并交换卡片。

<小时/>

例如，使用上面的代码:

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

public class CardLayoutTestPanel extends JPanel {
   public static final String CARD_JBUTTON = "Card JButton";
   public static final String CARD_JTEXTFIELD = "Card JTextField";
   public static final String CARD_JRADIOBUTTON = "Card JRadioButton";

   private static void createAndShowGui() {
      final CardLayoutTestPanel cardLayoutTestPanel = new CardLayoutTestPanel();

      JPanel buttonPanel = new JPanel(new GridLayout(1, 0, 5, 5));
      buttonPanel.setBorder(BorderFactory.createEmptyBorder(5, 5, 5, 5));
      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);

      previousButton.addActionListener(new ActionListener() {
         public void actionPerformed(ActionEvent ae) {
            cardLayoutTestPanel.previousCard();
         }
      });
      nextButton.addActionListener(new ActionListener() {
         public void actionPerformed(ActionEvent ae) {
            cardLayoutTestPanel.nextCard();
         }
      });

      JFrame frame = new JFrame("CardLayoutTest");
      frame.setDefaultCloseOperation(JFrame.DISPOSE_ON_CLOSE);
      frame.getContentPane().add(cardLayoutTestPanel);
      frame.getContentPane().add(buttonPanel, BorderLayout.PAGE_END);
      frame.pack();
      frame.setLocationByPlatform(true);
      frame.setVisible(true);
   }

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

   private CardLayout cardLayout = new CardLayout(20, 20);
   private JPanel cardShowingPanel = new JPanel(cardLayout);

   public CardLayoutTestPanel() {
      /*
       * 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();
      cardShowingPanel.add(win1, CARD_JBUTTON);
      Window2 win2 = new Window2();
      cardShowingPanel.add(win2, CARD_JTEXTFIELD);
      Window3 win3 = new Window3();
      cardShowingPanel.add(win3, CARD_JRADIOBUTTON);

      setLayout(new BorderLayout());

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

   public void nextCard() {
      cardLayout.next(cardShowingPanel);
   }

   public void previousCard() {
      cardLayout.previous(cardShowingPanel);
   }

   public void showCard(String key) {
      cardLayout.show(cardShowingPanel, key);
   }

}

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);
   }
}