java - 从单独的 JForm 访问 JComboBox 数据

Question

我花了一些时间浏览 Stack Overflow 和互联网寻找我的问题的答案，但我发现所有的答案都很难理解，而且我不确定它们是否与我的问题有关，所以我我决定在正确的情况下需要帮助。

我正在创建一个程序，它将根据输入的特定类型的图形给出一系列解决方案。我真诚地努力从第一个 JFrame 中的 JComboBox 中获取数据，并在第二个中显示它。

我有两个类，GraphEquationSolverGUI 和 DefineEquation。我使用的是 Netbeans IDE，GraphEquationSolverGUI 是我的“项目”。

GraphEquationSolverGUI:

private void graphSelectionActionPerformed(java.awt.event.ActionEvent evt) {                                               
    String graphSelectionGUI = (String)graphSelection.getSelectedItem();
    //graphSelectedTextField.setText(graphSelectionGUI);
    DefineEquation graphSelectedObj = new DefineEquation(graphSelectionGUI);
    graphSelectedObj.addItem(graphSelectionGUI);

这是 JComboBox，我希望在其中选择将数据发送到另一个类。 JComboBox 称为 graphSelection。您会注意到注释文本是我将 JTextField 设置为 JComboBox 的值，它在这个 JForm 内部，我自己用它来测试以确保数据输入正确，它可以工作并且我可以显示数据在同一个 JFrame 中。下面的其他代码是我尝试创建一个对象并通过它传递数据，我对对象有点生疏，因为我已经有一段时间没有使用它们了，如果我让你哭了，我很抱歉。

定义方程:

public DefineEquation(String graphSelected) {
    this.graphSelected = graphSelected;
} //If anyone cares here is my constructor for the object

public void addItem(String graphSelectedString1){
    DefineEquation graphSelectedObj = new DefineEquation(graphSelected);
    String graphSelectedStringMAIN = graphSelectedString1.toString();
    selectedGraph.setText(graphSelectedStringMAIN);
}

以上是我创建的将数据添加到名为 selectedGraph 的 JTextField 的方法。您会注意到我有 graphSelectedString1 和 graphSelectedStringMAIN，我在其中将 String 转换为显然多余的 String。我这样做只是为了以防万一，这是多余的，很抱歉让你畏缩了。

我知道这可能很难理解，您可能会发现很难理解我的问题。简单地说，我如何将数据从一个 JFrame JComboBox 传递到另一个 JFrame 中的 JTextField？我会使用对象吗？如果可以的话，请尝试引导我完成它，我很困惑。如果您想通读所有内容，我会将我的所有代码粘贴到下面。

GraphEquationSolverGUI:

/*
* To change this license header, choose License Headers in Project Properties.
 * To change this template file, choose Tools | Templates
 * and open the template in the editor.
 */
package GUI;

/**
 *
 * @author MatthewAlanTroutman
 */

public class GraphEquationSolverGUI extends javax.swing.JFrame {

/**
 * Creates new form GraphEquationSolverGUI
 */

public GraphEquationSolverGUI() {
    initComponents();
}


/**
 * This method is called from within the constructor to initialize the form.
 * WARNING: Do NOT modify this code. The content of this method is always
 * regenerated by the Form Editor.
 */
@SuppressWarnings("unchecked")
// <editor-fold defaultstate="collapsed" desc="Generated Code">                          
private void initComponents() {

    jSpinner1 = new javax.swing.JSpinner();
    welcome = new javax.swing.JLabel();
    programDescription = new javax.swing.JLabel();
    graphsOffered = new javax.swing.JLabel();
    linear = new javax.swing.JLabel();
    bilinear = new javax.swing.JLabel();
    quadratic = new javax.swing.JLabel();
    cubic = new javax.swing.JLabel();
    exponential = new javax.swing.JLabel();
    graphSelectionText = new javax.swing.JLabel();
    graphSelection = new javax.swing.JComboBox();
    help = new javax.swing.JButton();
    close = new javax.swing.JButton();
    next = new javax.swing.JButton();
    graphSelectedTextField = new javax.swing.JTextField();
    graphSelectedLabel = new javax.swing.JLabel();

    setDefaultCloseOperation(javax.swing.WindowConstants.EXIT_ON_CLOSE);
    setTitle("GraphEquationSolver");
    setBackground(new java.awt.Color(255, 255, 255));

    welcome.setFont(new java.awt.Font("Lucida Grande", 0, 48)); // NOI18N
    welcome.setHorizontalAlignment(javax.swing.SwingConstants.CENTER);
    welcome.setText("Welcome");
    welcome.setPreferredSize(new java.awt.Dimension(800, 100));

    programDescription.setFont(new java.awt.Font("Lucida Grande", 0, 14)); // NOI18N
    programDescription.setText("You can use this program to find a variety of solutions for different types of graphs, please select a graph to begin");
    programDescription.setPreferredSize(new java.awt.Dimension(800, 75));

    graphsOffered.setFont(new java.awt.Font("Lucida Grande", 0, 18)); // NOI18N
    graphsOffered.setText("Graphs we offer:");

    linear.setFont(new java.awt.Font("Lucida Grande", 0, 14)); // NOI18N
    linear.setText("- Linear");

    bilinear.setFont(new java.awt.Font("Lucida Grande", 0, 14)); // NOI18N
    bilinear.setText("- Bilinear");

    quadratic.setFont(new java.awt.Font("Lucida Grande", 0, 14)); // NOI18N
    quadratic.setText("- Quadratic");

    cubic.setFont(new java.awt.Font("Lucida Grande", 0, 14)); // NOI18N
    cubic.setText("- Cubic");

    exponential.setFont(new java.awt.Font("Lucida Grande", 0, 14)); // NOI18N
    exponential.setText("- Exponential");

    graphSelectionText.setFont(new java.awt.Font("Lucida Grande", 0, 18)); // NOI18N
    graphSelectionText.setText("Please select your graph");

    graphSelection.setModel(new javax.swing.DefaultComboBoxModel(new String[] { "Linear", "Bilinear", "Quadratic", "Cubic", "Exponential" }));
    graphSelection.setToolTipText("");
    graphSelection.addActionListener(new java.awt.event.ActionListener() {
        public void actionPerformed(java.awt.event.ActionEvent evt) {
            graphSelectionActionPerformed(evt);
        }
    });

    help.setFont(new java.awt.Font("Lucida Grande", 0, 48)); // NOI18N
    help.setText("Help");

    close.setFont(new java.awt.Font("Lucida Grande", 0, 48)); // NOI18N
    close.setText("Close");
    close.addActionListener(new java.awt.event.ActionListener() {
        public void actionPerformed(java.awt.event.ActionEvent evt) {
            closeActionPerformed(evt);
        }
    });

    next.setFont(new java.awt.Font("Lucida Grande", 0, 48)); // NOI18N
    next.setText("Next");
    next.addActionListener(new java.awt.event.ActionListener() {
        public void actionPerformed(java.awt.event.ActionEvent evt) {
            nextActionPerformed(evt);
        }
    });

    graphSelectedTextField.setEditable(false);

    graphSelectedLabel.setFont(new java.awt.Font("Lucida Grande", 0, 18)); // NOI18N
    graphSelectedLabel.setText("Graph Selected");

    javax.swing.GroupLayout layout = new javax.swing.GroupLayout(getContentPane());
    getContentPane().setLayout(layout);
    layout.setHorizontalGroup(
        layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
        .addGroup(javax.swing.GroupLayout.Alignment.TRAILING, layout.createSequentialGroup()
            .addContainerGap(javax.swing.GroupLayout.DEFAULT_SIZE, Short.MAX_VALUE)
            .addComponent(welcome, javax.swing.GroupLayout.PREFERRED_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.PREFERRED_SIZE)
            .addGap(240, 240, 240))
        .addGroup(layout.createSequentialGroup()
            .addGroup(layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
                .addGroup(layout.createSequentialGroup()
                    .addGap(240, 240, 240)
                    .addComponent(programDescription, javax.swing.GroupLayout.PREFERRED_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.PREFERRED_SIZE))
                .addGroup(layout.createSequentialGroup()
                    .addGap(184, 184, 184)
                    .addGroup(layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
                        .addComponent(exponential)
                        .addGroup(layout.createSequentialGroup()
                            .addGroup(layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
                                .addComponent(graphsOffered)
                                .addComponent(linear)
                                .addComponent(bilinear)
                                .addComponent(quadratic)
                                .addComponent(cubic))
                            .addGap(311, 311, 311)
                            .addGroup(layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING, false)
                                .addComponent(graphSelectionText, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, Short.MAX_VALUE)
                                .addComponent(graphSelection, 0, javax.swing.GroupLayout.DEFAULT_SIZE, Short.MAX_VALUE)
                                .addComponent(graphSelectedTextField)
                                .addComponent(graphSelectedLabel, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, Short.MAX_VALUE)))))
                .addGroup(layout.createSequentialGroup()
                    .addGap(231, 231, 231)
                    .addComponent(help, javax.swing.GroupLayout.PREFERRED_SIZE, 255, javax.swing.GroupLayout.PREFERRED_SIZE)
                    .addGap(18, 18, 18)
                    .addComponent(close, javax.swing.GroupLayout.PREFERRED_SIZE, 255, javax.swing.GroupLayout.PREFERRED_SIZE)
                    .addGap(18, 18, 18)
                    .addComponent(next, javax.swing.GroupLayout.PREFERRED_SIZE, 255, javax.swing.GroupLayout.PREFERRED_SIZE)))
            .addContainerGap(240, Short.MAX_VALUE))
    );
    layout.setVerticalGroup(
        layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
        .addGroup(layout.createSequentialGroup()
            .addGap(34, 34, 34)
            .addComponent(welcome, javax.swing.GroupLayout.PREFERRED_SIZE, 50, javax.swing.GroupLayout.PREFERRED_SIZE)
            .addPreferredGap(javax.swing.LayoutStyle.ComponentPlacement.RELATED)
            .addComponent(programDescription, javax.swing.GroupLayout.PREFERRED_SIZE, 27, javax.swing.GroupLayout.PREFERRED_SIZE)
            .addGap(73, 73, 73)
            .addGroup(layout.createParallelGroup(javax.swing.GroupLayout.Alignment.BASELINE)
                .addComponent(graphsOffered)
                .addComponent(graphSelectionText))
            .addPreferredGap(javax.swing.LayoutStyle.ComponentPlacement.RELATED)
            .addComponent(graphSelection, javax.swing.GroupLayout.PREFERRED_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.PREFERRED_SIZE)
            .addPreferredGap(javax.swing.LayoutStyle.ComponentPlacement.UNRELATED)
            .addGroup(layout.createParallelGroup(javax.swing.GroupLayout.Alignment.BASELINE)
                .addComponent(linear)
                .addComponent(graphSelectedLabel))
            .addPreferredGap(javax.swing.LayoutStyle.ComponentPlacement.RELATED)
            .addGroup(layout.createParallelGroup(javax.swing.GroupLayout.Alignment.TRAILING)
                .addGroup(layout.createSequentialGroup()
                    .addComponent(bilinear)
                    .addPreferredGap(javax.swing.LayoutStyle.ComponentPlacement.RELATED)
                    .addComponent(quadratic))
                .addComponent(graphSelectedTextField, javax.swing.GroupLayout.PREFERRED_SIZE, 28, javax.swing.GroupLayout.PREFERRED_SIZE))
            .addGroup(layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
                .addGroup(layout.createSequentialGroup()
                    .addPreferredGap(javax.swing.LayoutStyle.ComponentPlacement.RELATED)
                    .addComponent(cubic)
                    .addPreferredGap(javax.swing.LayoutStyle.ComponentPlacement.RELATED)
                    .addComponent(exponential)
                    .addContainerGap(javax.swing.GroupLayout.DEFAULT_SIZE, Short.MAX_VALUE))
                .addGroup(layout.createSequentialGroup()
                    .addPreferredGap(javax.swing.LayoutStyle.ComponentPlacement.RELATED, 219, Short.MAX_VALUE)
                    .addGroup(layout.createParallelGroup(javax.swing.GroupLayout.Alignment.BASELINE)
                        .addComponent(help, javax.swing.GroupLayout.PREFERRED_SIZE, 87, javax.swing.GroupLayout.PREFERRED_SIZE)
                        .addComponent(close, javax.swing.GroupLayout.PREFERRED_SIZE, 87, javax.swing.GroupLayout.PREFERRED_SIZE)
                        .addComponent(next, javax.swing.GroupLayout.PREFERRED_SIZE, 87, javax.swing.GroupLayout.PREFERRED_SIZE))
                    .addGap(169, 169, 169))))
    );

    graphSelection.getAccessibleContext().setAccessibleName("");
    help.getAccessibleContext().setAccessibleName("help");
    close.getAccessibleContext().setAccessibleName("close");

    pack();
}// </editor-fold>                        

private void graphSelectionActionPerformed(java.awt.event.ActionEvent evt) {                                               
    String graphSelectionGUI = (String)graphSelection.getSelectedItem();
    graphSelectedTextField.setText(graphSelectionGUI);
    //DefineEquation graphSelectedObj = new DefineEquation(graphSelectionGUI);
    //graphSelectedObj.addItem(graphSelectionGUI);

}                                              

private void closeActionPerformed(java.awt.event.ActionEvent evt) {                                      
    System.exit(0);
}                                     

private void nextActionPerformed(java.awt.event.ActionEvent evt) {                                     
    this.setVisible(false);
    new DefineEquation().setVisible(true);
}                                    

/**
 * @param args the command line arguments
 */
public static void main(String args[]) {
    /* Set the Nimbus look and feel */
    //<editor-fold defaultstate="collapsed" desc=" Look and feel setting code (optional) ">
    /* If Nimbus (introduced in Java SE 6) is not available, stay with the default look and feel.
     * For details see http://download.oracle.com/javase/tutorial/uiswing/lookandfeel/plaf.html 
     */
    try {
        for (javax.swing.UIManager.LookAndFeelInfo info : javax.swing.UIManager.getInstalledLookAndFeels()) {
            if ("Nimbus".equals(info.getName())) {
                javax.swing.UIManager.setLookAndFeel(info.getClassName());
                break;
            }
        }
    } catch (ClassNotFoundException ex) {
        java.util.logging.Logger.getLogger(GraphEquationSolverGUI.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
    } catch (InstantiationException ex) {
        java.util.logging.Logger.getLogger(GraphEquationSolverGUI.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
    } catch (IllegalAccessException ex) {
        java.util.logging.Logger.getLogger(GraphEquationSolverGUI.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
    } catch (javax.swing.UnsupportedLookAndFeelException ex) {
        java.util.logging.Logger.getLogger(GraphEquationSolverGUI.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
    }
    //</editor-fold>

    /* Create and display the form */
    java.awt.EventQueue.invokeLater(new Runnable() {
        public void run() {
            new GraphEquationSolverGUI().setVisible(true);
        }
    });
}

// Variables declaration - do not modify                     
private javax.swing.JLabel bilinear;
private javax.swing.JButton close;
private javax.swing.JLabel cubic;
private javax.swing.JLabel exponential;
private javax.swing.JLabel graphSelectedLabel;
private javax.swing.JTextField graphSelectedTextField;
private javax.swing.JComboBox graphSelection;
private javax.swing.JLabel graphSelectionText;
private javax.swing.JLabel graphsOffered;
private javax.swing.JButton help;
private javax.swing.JSpinner jSpinner1;
private javax.swing.JLabel linear;
private javax.swing.JButton next;
private javax.swing.JLabel programDescription;
private javax.swing.JLabel quadratic;
private javax.swing.JLabel welcome;
// End of variables declaration                   
}

定义方程:

/*
 * To change this license header, choose License Headers in Project Properties.
 * To change this template file, choose Tools | Templates
 * and open the template in the editor.
 */
package GUI;

/**
 *
 * @author MatthewAlanTroutman
 */
public class DefineEquation extends javax.swing.JFrame {
//public class DefineEquation extends GraphEquationSolverGUI {
public String graphSelected;

/**
 * Creates new form DefineEquation
 */
public DefineEquation() {
    initComponents();
}
public DefineEquation(String graphSelected) {
    this.graphSelected = graphSelected;
}



/**
 * This method is called from within the constructor to initialize the form.
 * WARNING: Do NOT modify this code. The content of this method is always
 * regenerated by the Form Editor.
 */
@SuppressWarnings("unchecked")
// <editor-fold defaultstate="collapsed" desc="Generated Code">                          
private void initComponents() {

    selectedGraph = new javax.swing.JTextField();

    setDefaultCloseOperation(javax.swing.WindowConstants.EXIT_ON_CLOSE);

    selectedGraph.setEditable(false);
    selectedGraph.addActionListener(new java.awt.event.ActionListener() {
        public void actionPerformed(java.awt.event.ActionEvent evt) {
            selectedGraphActionPerformed(evt);
        }
    });

    javax.swing.GroupLayout layout = new javax.swing.GroupLayout(getContentPane());
    getContentPane().setLayout(layout);
    layout.setHorizontalGroup(
        layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
        .addGroup(layout.createSequentialGroup()
            .addGap(435, 435, 435)
            .addComponent(selectedGraph, javax.swing.GroupLayout.PREFERRED_SIZE, 249, javax.swing.GroupLayout.PREFERRED_SIZE)
            .addContainerGap(596, Short.MAX_VALUE))
    );
    layout.setVerticalGroup(
        layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
        .addGroup(layout.createSequentialGroup()
            .addGap(126, 126, 126)
            .addComponent(selectedGraph, javax.swing.GroupLayout.PREFERRED_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.PREFERRED_SIZE)
            .addContainerGap(646, Short.MAX_VALUE))
    );

    pack();
}// </editor-fold>                        

private void selectedGraphActionPerformed(java.awt.event.ActionEvent evt) {                                              

}                                             
public void addItem(String graphSelectedString1){
    DefineEquation graphSelectedObj = new DefineEquation(graphSelected);
    String graphSelectedStringMAIN = graphSelectedString1.toString();
    selectedGraph.setText(graphSelectedStringMAIN);
}

/**
 * @param args the command line arguments
 */
public static void main(String args[]) {
    /* Set the Nimbus look and feel */
    //<editor-fold defaultstate="collapsed" desc=" Look and feel setting code (optional) ">
    /* If Nimbus (introduced in Java SE 6) is not available, stay with the default look and feel.
     * For details see http://download.oracle.com/javase/tutorial/uiswing/lookandfeel/plaf.html 
     */
    try {
        for (javax.swing.UIManager.LookAndFeelInfo info : javax.swing.UIManager.getInstalledLookAndFeels()) {
            if ("Nimbus".equals(info.getName())) {
                javax.swing.UIManager.setLookAndFeel(info.getClassName());
                break;
            }
        }
    } catch (ClassNotFoundException ex) {
        java.util.logging.Logger.getLogger(DefineEquation.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
    } catch (InstantiationException ex) {
        java.util.logging.Logger.getLogger(DefineEquation.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
    } catch (IllegalAccessException ex) {
        java.util.logging.Logger.getLogger(DefineEquation.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
    } catch (javax.swing.UnsupportedLookAndFeelException ex) {
        java.util.logging.Logger.getLogger(DefineEquation.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
    }
    //</editor-fold>

    /* Create and display the form */
    java.awt.EventQueue.invokeLater(new Runnable() {
        public void run() {
            new DefineEquation().setVisible(true);
        }

    });
}

// Variables declaration - do not modify                     
private javax.swing.JTextField selectedGraph;
// End of variables declaration                   
}

您会注意到我试图“扩展”我的第一个 JFrame，但这导致第二个 JFrame“窗口”以某种方式与第一个 JFrame“窗口”结合。

概念图:

编辑 1:这是完成它的最佳方式吗？如果是这样，我将如何移动数据？对象目前让我感到困惑，还有一些非静态和静态问题，这些问题似乎无效，因为我没有任何静态问题。如果这不是最好的方法，我该怎么办？我要 sleep 了，请评论说出你的建议和帮助，我不仅绝望，而且感到迷茫。

编辑 2:我正在尝试使用 m.cekiera 的答案，请在回答之前引用他的答案，因为这可能会有帮助。

编辑 3:仍然卡住了，需要详细帮助，很抱歉这么苛刻，但我无法解决这个问题。

编辑 4:我认为我找到了重大突破。我已经想出如何解决这个问题，但我真的认为我需要理解这一点。不管怎样，我有一个新类(class)和一个不同类(class)的新文本字段。我仍然有问题，我无法显示文本字段的值，但由于某种原因我可以输出相同的值。我想这更容易显示

所以这是 SelectSolutionsQuadratic 类:

public void displayText(String textToSet) {
    displayQuadraticEquation.setText(textToSet);
    System.out.println(textToSet);
}

这是 DefineEquationQuadratic:

private void nextActionPerformed(java.awt.event.ActionEvent evt) {                                     
    this.setVisible(false);
    new SelectSolutionsQuadratic().setVisible(true);
    SelectSolutionsQuadratic transferMe = new SelectSolutionsQuadratic();
    transferData = aQuadraticSpinner.getValue().toString() + " " + addSubQuadraticComboBox.getSelectedItem(); 
    transferMe.displayText(transferData);
}                     

所以基本上我只是很困惑为什么我可以将一个值从 DefineEquationQuadratic 发送到 SelectSolutionsQuadratic，然后用 System.out.println() 输出它；但不将文本字段设置为该值

Answer 1

我的建议是创建两个 JPanel 类，一个保存 JComboBox，另一个显示或需要结果。假设您已经这样做并调用了第一个类 HoldsComboBoxPanel，您的第二个类被称为 ShowSelectionPanel，那么您将为 HoldsComboBoxPanel 提供两个方法，一个是获取当前选择，一个“getter”方法，以及另一个允许外部类将 ActionListener 添加到组合框的方法。例如，简而言之，像这样:

public class HoldsComboBoxPanel extends JPanel {
   public static final String NAME = "holds combobox panel";
   // sample data
   private static final String[] DATA = { "Monday", "Tuesday", "Wednesday",
         "Thursday", "Friday" };
   private JComboBox<String> comboBox = new JComboBox<>(DATA);

   public HoldsComboBoxPanel() {
       // add the comboBox into our class here
   }

   // method to add a listener
   public void addComboBoxListener(ActionListener listener) {
      comboBox.addActionListener(listener);
   }

   // getter method
   public String getComboSelection() {
      return (String) comboBox.getSelectedItem();
   }

}

您的第二个类，即需要数据的类，将有一个 setter 方法，以允许外部类能够将组合选择插入其中。假设它有一个名为 displayField 的 JTextField 来显示选择，它的代码可能如下所示:

public class ShowSelectionPanel extends JPanel {
   public static final String NAME = "show selection panel";
   private JTextField displayField = new JTextField(10);

   public ShowSelectionPanel() {
      // add the displayField to the JPanel here
   }

   // setter method
   public void setDisplayText(String text) {
      displayField.setText(text);
      // or do whatever else you want to do with the selection
   }
}

然后您将有另一个使用 CardLayout 并允许在上面的 View JPanel 之间交换的类，例如称为 MainPanel。它可以使用 CardLayout 来允许您交换 JPanel，有一个公共(public)方法来允许外部类交换“卡片”JPanel，并且它会同时包含 HoldsComboBoxPanel 字段和 ShowSelectionPanel 字段，并且可以通过将 ActionListener 添加到像这样的组合框:

public class MainPanel extends JPanel {
   private CardLayout cardLayout = new CardLayout();
   private MenuPanel menuPanel = new MenuPanel();
   private HoldsComboBoxPanel holdsComboBoxPanel = new HoldsComboBoxPanel();
   private ShowSelectionPanel showSelectionPanel = new ShowSelectionPanel();

   public MainPanel() {
      // add an ActionListener to the JComboBox
      holdsComboBoxPanel.addComboBoxListener(new ActionListener() {

         @Override
         public void actionPerformed(ActionEvent e) {
            // get the combo's selected String
            String selection = holdsComboBoxPanel.getComboSelection();
            if (selection != null) {
               // push it into showSelection
               showSelectionPanel.setDisplayText(selection);
            }
         }
      });

      setLayout(cardLayout);
      add(menuPanel, MenuPanel.NAME);
      add(holdsComboBoxPanel, HoldsComboBoxPanel.NAME);
      add(showSelectionPanel, ShowSelectionPanel.NAME);
   }

   // method that allows outside classes to swap views
   public void showCard(String key) {
      cardLayout.show(this, key);
   }
}

带有一些额外代码以允许在“卡片”中移动的整个过程可能看起来像这样:

import java.awt.BorderLayout;
import java.awt.CardLayout;
import java.awt.Component;
import java.awt.Container;
import java.awt.Dimension;
import java.awt.GridBagLayout;
import java.awt.GridLayout;
import java.awt.Window;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.awt.event.KeyEvent;

import javax.swing.AbstractAction;
import javax.swing.AbstractButton;
import javax.swing.Action;
import javax.swing.BorderFactory;
import javax.swing.JButton;
import javax.swing.JComboBox;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.JPopupMenu;
import javax.swing.JTextField;
import javax.swing.SwingUtilities;

public class SimpleMultPanels {
   private static void createAndShowGui() {
      // create JFrame
      JFrame frame = new JFrame("SimpleMultPanels");
      frame.setDefaultCloseOperation(JFrame.DISPOSE_ON_CLOSE);

      // add our MainPanel to the JFrame
      frame.getContentPane().add(new MainPanel());
      frame.pack(); // pack it
      frame.setLocationByPlatform(true);
      frame.setVisible(true); // show it
   }

   public static void main(String[] args) {
      // this is for starting our Swing app on the event thread
      SwingUtilities.invokeLater(new Runnable() {
         public void run() {
            createAndShowGui();
         }
      });
   }
}

@SuppressWarnings("serial")
class MainPanel extends JPanel {
   private CardLayout cardLayout = new CardLayout();

   // the three "card" JPanels that this JPanel displays:
   private MenuPanel menuPanel = new MenuPanel();
   private HoldsComboBoxPanel holdsComboBoxPanel = new HoldsComboBoxPanel();
   private ShowSelectionPanel showSelectionPanel = new ShowSelectionPanel();

   // Actions for our JButtons
   private ExitAction exitAction = new ExitAction();
   private ShowAction backToMenuAction = new ShowAction(this, "Back to Menu",
         MenuPanel.NAME, KeyEvent.VK_B);
   private ShowAction toHoldsComboAction = new ShowAction(this, "Combo Panel",
         HoldsComboBoxPanel.NAME, KeyEvent.VK_C);
   private ShowAction toShowSelectionAction = new ShowAction(this,
         "Show Selection", ShowSelectionPanel.NAME, KeyEvent.VK_S);

   public MainPanel() {
      // add an ActionListener to the JComboBox
      holdsComboBoxPanel.addComboBoxListener(new ActionListener() {

         @Override
         public void actionPerformed(ActionEvent e) {
            // get the combo's selected String
            String selection = holdsComboBoxPanel.getComboSelection();
            if (selection != null) {
               // push it into showSelection
               showSelectionPanel.setDisplayText(selection);
            }
         }
      });

      // add Actions to class to allow swapping of cards and
      holdsComboBoxPanel.addButtonAction(backToMenuAction);
      holdsComboBoxPanel.addButtonAction(toShowSelectionAction);
      holdsComboBoxPanel.addButtonAction(exitAction); // and to exit gui

      showSelectionPanel.addButtonAction(backToMenuAction);
      showSelectionPanel.addButtonAction(toHoldsComboAction);
      showSelectionPanel.addButtonAction(exitAction);

      menuPanel.addButtonAction(toHoldsComboAction);
      menuPanel.addButtonAction(toShowSelectionAction);
      menuPanel.addButtonAction(exitAction);

      setBorder(BorderFactory.createEmptyBorder(5, 5, 5, 5));

      // set our layout
      setLayout(cardLayout);

      // and add our "card" JPanels
      add(menuPanel, MenuPanel.NAME);
      add(holdsComboBoxPanel, HoldsComboBoxPanel.NAME);
      add(showSelectionPanel, ShowSelectionPanel.NAME);
   }

   // method that allows outside classes to swap views
   public void showCard(String key) {
      cardLayout.show(this, key);
   }
}

@SuppressWarnings("serial")
class HoldsComboBoxPanel extends JPanel {
   // constant String that will be used by the CardLayout
   public static final String NAME = "holds combobox panel";

   // sample data
   private static final String[] DATA = { "Monday", "Tuesday", "Wednesday",
         "Thursday", "Friday" };
   private JComboBox<String> comboBox = new JComboBox<>(DATA);

   // JPanel to hold buttons to allow moving between cards
   private JPanel buttonPanel = new JPanel(new GridLayout(1, 0, 5, 0));

   public HoldsComboBoxPanel() {
      comboBox.setSelectedIndex(-1);
      JPanel centerPanel = new JPanel();
      centerPanel.add(comboBox);

      setLayout(new BorderLayout());
      add(centerPanel, BorderLayout.CENTER);
      add(buttonPanel, BorderLayout.SOUTH);
   }

   // method to add a listener
   public void addComboBoxListener(ActionListener listener) {
      comboBox.addActionListener(listener);
   }

   // getter method
   public String getComboSelection() {
      return (String) comboBox.getSelectedItem();
   }

   // create a new JButton with an Action and add to buttonPanel
   public void addButtonAction(Action action) {
      buttonPanel.add(new JButton(action));
   }
}

@SuppressWarnings("serial")
class ShowSelectionPanel extends JPanel {
   public static final String NAME = "show selection panel";
   private static final int PREF_W = 300;
   private static final int PREF_H = PREF_W;
   private JTextField displayField = new JTextField(10);
   private JPanel buttonPanel = new JPanel(new GridLayout(1, 0, 5, 0));

   public ShowSelectionPanel() {
      displayField.setFocusable(false);

      JPanel centerPanel = new JPanel();
      centerPanel.add(displayField);

      setLayout(new BorderLayout());
      add(centerPanel, BorderLayout.CENTER);
      add(buttonPanel, BorderLayout.SOUTH);
   }

   // code to make our GUI a little larger
   @Override
   public Dimension getPreferredSize() {
      Dimension superSz = super.getPreferredSize();
      if (isPreferredSizeSet()) {
         return superSz;
      }
      int prefW = Math.max(superSz.width, PREF_W);
      int prefH = Math.max(superSz.height, PREF_H);
      return new Dimension(prefW, prefH);
   }

   // setter method
   public void setDisplayText(String text) {
      displayField.setText(text);
      // or do whatever else you want to do with the selection
   }

   public void addButtonAction(Action action) {
      buttonPanel.add(new JButton(action));
   }

}

@SuppressWarnings("serial")
class MenuPanel extends JPanel {
   public static final String NAME = "menu panel";
   private JPanel buttonPanel = new JPanel(new GridLayout(0, 1, 0, 5));

   public MenuPanel() {
      setLayout(new GridBagLayout());
      add(buttonPanel);
   }

   public void addButtonAction(Action action) {
      buttonPanel.add(new JButton(action));
   }
}

@SuppressWarnings("serial")
class ShowAction extends AbstractAction {
   private MainPanel mainPanel;
   private String key;

   /**
    * Abstract Action used by JButtons
    * @param mainPanel: the JPanel that uses the CardLayout
    * @param name: The name displayed by the button
    * @param key: The key used in the CardLayout#show(String key) mehtod
    * @param mnemonic: the JButton's mnemonic char
    */
   public ShowAction(MainPanel mainPanel, String name, String key, int mnemonic) {
      super(name);
      putValue(MNEMONIC_KEY, mnemonic);
      this.mainPanel = mainPanel;
      this.key = key;
   }

   @Override
   public void actionPerformed(ActionEvent e) {
      // tell the mainPanel to show the card associated with the key
      mainPanel.showCard(key);
   }
}

// class of mine to allow disposing of a window
// It's a little complex to allow it to work with either a JButton
// or a JMenuItem
@SuppressWarnings("serial")
class ExitAction extends AbstractAction {
   public ExitAction() {
      super("Exit");
      putValue(MNEMONIC_KEY, KeyEvent.VK_X);
   }

   @Override
   public void actionPerformed(ActionEvent e) {
      // get the button that caused this action
      Object source = e.getSource();
      if (source instanceof AbstractButton) {
         AbstractButton exitButton = (AbstractButton) source;

         // get the parent top level window
         Window topWindow = SwingUtilities.getWindowAncestor(exitButton);
         if (topWindow == null) { // if null, then likely in a JMenuItem
            // so we have to get its jpopupmenu parent
            Container parent = exitButton.getParent();
            if (parent instanceof JPopupMenu) {
               JPopupMenu popupMenu = (JPopupMenu) parent;

               // get the invoker for the pop up menu
               Component invoker = popupMenu.getInvoker();
               if (invoker != null) {
                  // and get *its* top level window
                  topWindow = SwingUtilities.getWindowAncestor(invoker);
               }
            }
         }
         if (topWindow != null) {
            // dispose of the top-level window
            topWindow.dispose();
         }
      }
   }
}