在CardLayout中的卡之间切换时调用方法

Question

我是Java新手，但是CardLayout有问题。我有一个CardLayout，有两张卡。我在第一个面板（卡布局的第一张卡片）中有3个单选按钮，第二个面板的内容取决于我在第一个面板中选择的内容。

因此，当我在面板之间切换时（检查一些单选按钮之后），需要创建此组件，但是在运行程序时会创建它。组件是在第二个面板的构造函数中创建的（组件称为ChartComponent），因此是在创建第二个面板时创建的，但是我不知道如何在两个面板之间切换时如何创建它。我尝试在Second Panel中创建一个方法，该方法将在切换面板时创建组件并运行它，但这似乎不起作用。

MainMenu：

public class MainMenu_V1 extends JFrame {

    private JMenuBar menuBar;
    private JMenu file;
    private JMenuItem exit;
    private JPanel mainPanel;
    private JMenuItem back;
    private SecondPanel sec;
    CardLayout cardLayout = new CardLayout();

    public MainMenu_V1() throws IOException{
        setTitle("My Layout");
        setResizable(true);
        setExtendedState(JFrame.MAXIMIZED_BOTH); 
        setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        setJMenuBar(createMainMenu());
        setLocationRelativeTo(null);

        mainPanel = new JPanel();
        mainPanel.setLayout(cardLayout);
        sec = new SecondPanel(mainPanel);
        mainPanel.add(new FirstPanel(mainPanel), "FIRST");
        mainPanel.add(sec, "SECOND");

        setContentPane(mainPanel);
    }

    public JMenuBar createMainMenu() {
        menuBar = new JMenuBar();
        file = new JMenu("Menu");
        exit = new JMenuItem("Exit");
        back = new JMenuItem("<-");
        exit.addActionListener(new ActionListener() {
            @Override
            public void actionPerformed(ActionEvent e) {
                System.exit(0);
            }
        });

        back.addActionListener(new ActionListener() {
            @Override
            public void actionPerformed(ActionEvent e) {

                cardLayout.first(mainPanel);
            }
        });

        file.add(back);
        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) throws IOException {
        new MainMenu_V1().setVisible(true);
    }
}

第一张卡片：

public class FirstPanel extends JPanel {

    private JButton button;
    private JPanel mainPanel;
    JRadioButton randomButton;
    JRadioButton customButton;
    JRadioButton fileButton;
    private File inputfile;
    private String aWay;
    JButton createButton = new JButton("Create graph");
    JButton Mode1 = new JButton("Mode 1");
    JButton Mode2 = new JButton("Mode 2");
    JButton Mode3 = new JButton("Mode 3");
    final String random = "Randomize";
    final String custom = "Custom";
    final String file = "File";
    FlowLayout chromLayout = new FlowLayout();
    JLabel imageLabel = new JLabel();

    public FirstPanel(JPanel mainPanel) throws IOException {
        this.mainPanel = mainPanel;
        final JPanel panel = new JPanel();
        panel.setLayout(chromLayout);
        JPanel controls = new JPanel();
        setLayout(new BorderLayout());
        controls.setLayout(new FlowLayout());
        //create radiobuttons
        randomButton = new JRadioButton(random);
        randomButton.setActionCommand(random);
        randomButton.setSelected(true);
        customButton = new JRadioButton(custom);
        customButton.setActionCommand(custom);
        fileButton = new JRadioButton(file);
        fileButton.setActionCommand(file);
        //add controls to create graphs
        final ButtonGroup group = new ButtonGroup();
        group.add(randomButton);
        group.add(customButton);
        group.add(fileButton);
        controls.add(randomButton);
        controls.add(customButton);
        controls.add(fileButton);
        try {
            ImageIcon ii = new ImageIcon(this.getClass().getResource("gif2.gif"));
            imageLabel.setIcon(ii);

        } catch (Exception exception) {
            exception.printStackTrace();
        }

        //set action listener


        Mode1.addActionListener(new ActionListener() {
            public void actionPerformed(ActionEvent e) {
                String command = group.getSelection().getActionCommand();
                ReadAdjMatrix r = new ReadAdjMatrix();
                try { r.setGraph(command);
                    MainMenu_V1 main = new MainMenu_V1();
                    main.switchPanel(mainPanel, "SECOND");
                } catch (IOException ex) { ex.printStackTrace(); }
                //Check the selection

            }
        });
        panel.add(Mode1);
        panel.add(Mode2);
        panel.add(Mode3);
        add(panel, BorderLayout.NORTH);
        add(controls, BorderLayout.SOUTH);
        add(imageLabel, BorderLayout.CENTER);
    }
}

第二张卡：

public class SecondPanel extends JPanel {

    private JButton button;
    private JPanel mainPanel;


    public SecondPanel(JPanel mainPanel) throws FileNotFoundException {
        this.mainPanel = mainPanel;
        setLayout(new BorderLayout());
        add(new ChartComponent(), BorderLayout.CENTER);
}

编辑：

我尝试通过这种方式编辑第二个面板： 公共类SecondPanel扩展了JPanel {

private JButton button;
private JPanel mainPanel;


public SecondPanel(JPanel mainPanel) throws FileNotFoundException {
    this.mainPanel = mainPanel;
    //setPreferredSize(new Dimension(400, 200));
    setLayout(new BorderLayout());

}
public void createComp() {
    add(new ChartComponent(), BorderLayout.CENTER);
}

}

并通过以下方式在MainMenu中切换面板：

public void switchPanel(Container container, String panelName) {
    if (panelName == "SECOND") { sec.createComp(); }
    CardLayout card = (CardLayout) (container.getLayout());
    card.show(container, panelName);
}

但是当我这样做时，组件并不是全部创建。