CardLayout 不切换卡片

Question

首先，我没有收到任何错误。所以这可能是一个逻辑错误。 我正在尝试切换到playMenu 面板，但是当我按下按钮（在mainMenu 类中）时，什么也没有发生。是的，方法switchCard 被调用，因为我用一个简单的println. 进行了检查

这是包含内容面板的 Frame 类。

我删除了不相关的变量。

//Panel Final Names
    private final String MENU_ID = "menu";
    private final String PLAY_ID = "play";

    //Panels(Cards)
    private MainMenu mainMenu;
    private Play playMenu;

    //JFrame
    private JFrame frame = new JFrame("Battleships");

    //Panel that will hold the card panel
    private CardLayout cl = new CardLayout();
    private JPanel contentPanel = new JPanel(cl);

    //Constructors
    public Frame(){}

    public Frame(boolean x){
        GUI();
    }

    public void GUI(){
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        frame.setResizable(false);

        /*
            Passing Parameters to MainMenu class so
            you can do operations like changing panels and
            disposing the main JFrame from a different class
        */
        mainMenu = new MainMenu(frame, contentPanel);
        playMenu = new Play(frame, contentPanel);

//Adding menu panel as a card in contentPanel
        contentPanel.add(mainMenu, MENU_ID);
        contentPanel.add(playMenu, PLAY_ID);

        //Adding contentPanel to JFrame
        frame.add(contentPanel, BorderLayout.CENTER);

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


    }

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

    public void switchCard(){
        contentPanel.setLayout(new CardLayout());
        CardLayout cl = (CardLayout) contentPanel.getLayout();
        cl.show(contentPanel, PLAY_ID);
    }

这是我要切换到的 JPanel。我删除了 NetBeans 自动生成的代码。如果它以某种方式与这个问题相关，我会发布它。

public class Play extends javax.swing.JPanel {

    /**
     * Creates new form Play
     */

    private JFrame parentFrame;
    private JPanel contentPanel;

    public Play(JFrame frameIn, JPanel panelIn) {
        initComponents();
        contentPanel = panelIn;
        parentFrame = frameIn;
    }

}

Answer 1

这行不通：

public void switchCard(){
    contentPanel.setLayout(new CardLayout());
    CardLayout cl = (CardLayout) contentPanel.getLayout();
    cl.show(contentPanel, PLAY_ID);
}

因为您正在更改原始布局，即包含所有数据的布局。相反，不要设置 contentPane 的布局，而是使用已经存在的布局。

public void switchCard(){
    // contentPanel.setLayout(new CardLayout());
    CardLayout cl = (CardLayout) contentPanel.getLayout();
    cl.show(contentPanel, PLAY_ID);
}

就此而言，您可以使用已有的cl 字段。例如：

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

public class BattleShipSwap {
   // make id's public
   public static final String MENU_ID = "menu";
   public static final String PLAY_ID = "play";

   private MainMenu mainMenu;
   private Play playMenu;

   private JFrame frame = new JFrame("Battleships");

   private CardLayout cl = new CardLayout();
   private JPanel contentPanel = new JPanel(cl);

   public BattleShipSwap() {
      initGui();
   }

   public void initGui() {
      frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
      frame.setResizable(false);

      mainMenu = new MainMenu(this);
      playMenu = new Play(this);

      contentPanel.add(mainMenu, MENU_ID);
      contentPanel.add(playMenu, PLAY_ID);

      frame.add(contentPanel, BorderLayout.CENTER);

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

   }

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

   public void switchCard(String id) {
      // contentPanel.setLayout(new CardLayout());
      // CardLayout cardlayout = (CardLayout) contentPanel.getLayout();

      // why not just use the field?
      cl.show(contentPanel, id);
   }
}

class MainMenu extends JPanel {
   private BattleShipSwap battleShipSwap;

   public MainMenu(BattleShipSwap battleShipSwap) {
      setBorder(BorderFactory.createTitledBorder("Main Menu"));
      this.battleShipSwap = battleShipSwap;

      add(new JButton(new SwapButtonAction(battleShipSwap, BattleShipSwap.PLAY_ID)));
   }

}

class Play extends JPanel {
   private BattleShipSwap battleShipSwap;

   public Play(BattleShipSwap battleShipSwap) {
      setBorder(BorderFactory.createTitledBorder("Play Menu"));
      this.battleShipSwap = battleShipSwap;

      add(new JButton(new SwapButtonAction(battleShipSwap, BattleShipSwap.MENU_ID)));
   }
}

class SwapButtonAction extends AbstractAction {
   private BattleShipSwap battleShipSwap;
   private String id;

   public SwapButtonAction(BattleShipSwap battleShipSwap, String id) {
      super("Swap");
      putValue(MNEMONIC_KEY, KeyEvent.VK_S);
      this.battleShipSwap = battleShipSwap;
      this.id = id;
   }

   @Override
   public void actionPerformed(ActionEvent arg0) {
      battleShipSwap.switchCard(id);
   }
}

将来，您将希望创建一个最小的可编译和可运行的示例程序，类似于我上面的程序，它演示了您的问题，MCVE