Question

我一直在寻找解决方案一段时间，尽管有类似的问题和答案，但发现似乎没有任何效果。我希望用户能够在卡片布局中设置各种面板。但是，我希望用于在这些卡之间切换的按钮位于卡本身上，而不是一组单独的按钮，这些按钮不会在程序中发生变化。这是创建框架的主文件：

public class BattleGraphs_V1 
{
    JPanel cards;

    public int cardNumber = 1;

    public void addComponentToPane (Container pane)
    {
        JPanel MainMenuCard = new MainMenu_V1();
        JPanel DifficultySelectorCard = new DifficultySelector_V1();

        cards = new JPanel(new CardLayout());

        cards.add(MainMenuCard);
        cards.add(DifficultySelectorCard);

        pane.add(cards, BorderLayout.CENTER);
    }

    private static void createAndShowGUI() 
    {
        JFrame frame = new JFrame("BattleGraphs");
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

        frame.setDefaultCloseOperation(javax.swing.WindowConstants.EXIT_ON_CLOSE);
        frame.setPreferredSize(new java.awt.Dimension(725, 420));
        frame.setResizable(false);

        BattleGraphs_V1 containerPanel = new BattleGraphs_V1();
        containerPanel.addComponentToPane(frame.getContentPane());

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

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

这两个面板（将来会有更多）在项目中有两个单独的文件。除了每个面板上单个按钮的动作监听器之外，我还没有为它们添加代码，它是所有自动生成的代码。

编辑：我向MainMenu JPanel的按钮添加了一个自动生成的动作侦听器，如下所示：

private void MainMenuCardSBActionPerformed(java.awt.event.ActionEvent evt) {                                               
        BattleGraphs_V1 BG_V1 = new BattleGraphs_V1();
        CardLayout cardLayout = (CardLayout) (BG_V1.cards.getLayout());
        cardLayout.show(BG_V1.cards, "DifficultyCard");
    }

在主文件（主文件为BattleGraphs_V1）中添加的名称添加后，如下所示：

cards.add(MainMenuCard, "MainMenuCard");
cards.add(DifficultySelectorCard, "DifficultyCard");

当我运行程序并单击该按钮时，得到了一个空指针异常错误，正如我已经完成了类似的解决方案。假设这更多地归结为范围问题，我会错吗？

第二次编辑： 是的，希望这应该有所帮助，我已将enite项目添加到GitHub存储库 - https://github.com/charga600/BattleGraphs/tree/master

Answer 1

当您将卡片添加到面板时，您应该将它们命名为，以便您可以选择要在特定事件中显示的开关。

cards = new JPanel(new CardLayout());

cards.add(MainMenuCard, "first");
cards.add(DifficultySelectorCard, "second");

pane.add(cards, BorderLayout.CENTER);

GUI：

JButton button = new JButton("Click here");
button.addActionListener(new ActionListener() {
    @Override
    public void actionPerformed(ActionEvent e) {
        CardLayout cl = (CardLayout) (cards.getLayout());
        cl.show(cards, "second");
    }
});

修改

这是演示CardLayout的简短示例，因为您没有共享完整的代码。

主要课程

public class MainMenu_V1 extends JFrame { private JMenuBar menuBar; private JMenu file; private JMenuItem exit; private JPanel mainPanel; public MainMenu_V1() { setTitle("Main Panel"); setResizable(false); setSize(new Dimension(400, 200)); setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE); setJMenuBar(createMainMenu()); setLocationRelativeTo(null); mainPanel = new JPanel(); mainPanel.setLayout(new CardLayout()); mainPanel.add(new FirstPanel(mainPanel), "FIRST"); mainPanel.add(new SecondPanel(mainPanel), "SECOND"); setContentPane(mainPanel); } public JMenuBar createMainMenu() { menuBar = new JMenuBar(); file = new JMenu("File"); exit = new JMenuItem("Exit"); exit.addActionListener(new ActionListener() { @Override public void actionPerformed(ActionEvent e) { System.exit(0); } }); file.add(exit); menuBar.add(file); return menuBar; } public void switchPanel(Container container, String panelName) { CardLayout card = (CardLayout) (container.getLayout()); card.show(container, panelName); } public static void main(String[] args) { javax.swing.SwingUtilities.invokeLater(new Runnable() { public void run() { new MainMenu_V1().setVisible(true); } }); } }

第一小组

public class FirstPanel extends JPanel { private JButton button; private JPanel mainPanel; public FirstPanel(JPanel mainPanel) { this.mainPanel = mainPanel; setPreferredSize(new Dimension(400, 200)); setBackground(Color.GRAY); add(createButton()); } private JButton createButton() { button = new JButton("Switch to the second Panel"); button.addActionListener(new ActionListener() { @Override public void actionPerformed(ActionEvent e) { MainMenu_V1 main = new MainMenu_V1(); main.switchPanel(mainPanel, "SECOND"); } }); return button; } }

第二个小组

public class SecondPanel extends JPanel { private JButton button; private JPanel mainPanel; public SecondPanel(JPanel mainPanel) { this.mainPanel = mainPanel; setPreferredSize(new Dimension(400, 200)); setBackground(Color.ORANGE); add(createButton()); } private JButton createButton() { button = new JButton("Switch to the first Panel"); button.addActionListener(new ActionListener() { @Override public void actionPerformed(ActionEvent e) { MainMenu_V1 main = new MainMenu_V1(); main.switchPanel(mainPanel, "FIRST"); } }); return button; } }

如何从卡上的按钮切换卡？

1 个答案: