使用组合框更改卡片布局的卡片

Question

我没有完全使应用程序正常运行。但是直到现在，在我编译并运行它之后，什么都没有出现。

（稍后会有一个名为“ UnitCircle”的类。我希望用户单击菜单将面板切换到该游戏面板）

public class TrigCrashCourse extends JFrame implements ActionListener
{
    //labels for main page
    private JFrame frame;

    private CardLayout cardlayout;
    private Container c; // contains the cards for different games

    //for menus
    private JMenu menu;
    private JMenuBar menubar;
    private JMenuItem item1;
    private JMenuItem item2;
    private JMenuItem item3;

    //for labels
    private JLabel label1;
    private JLabel label2;
    private JLabel label3;

    public static void main(String[]args)
    {
        TrigCrashCourse tcc = new TrigCrashCourse();
        tcc.runIt();
    }

    public void runIt()
    {
        frame = new JFrame("Trig Crash Course");
        frame.setSize(500,500);
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        frame.setLocation(10,20);
        frame.setResizable(true);
        frame.setVisible(true);

        //card layouts 
        c = getContentPane();
        cardlayout = new CardLayout();
        c.setLayout(cardlayout);

        UnitCircle uc = new UnitCircle();
        c.add("Unit Circle Game",uc);

        //menus
        item1 = new JMenuItem("Unit Circle");
        item2 = new JMenuItem("Pythagorean theorem");
        item3 = new JMenuItem("Graphing");
        menu = new JMenu("Choose a game");
        menubar = new JMenuBar();

        menu.add(item1);
        menu.add(item2);
        menu.add(item3);
        menubar.add(menu);

        item1.addActionListener(this);
        item2.addActionListener(this);
        item3.addActionListener(this);

        c.add(menubar);

        //labels
        setLayout(new FlowLayout());

        label1 = new JLabel("Trig Crash Course");
        label2 = new JLabel("-Alg2 Trig");
        label3 = new JLabel("You have 3 games to choose from");

        label1.setFont(new Font("serif",Font.BOLD,20));
        label2.setFont(new Font("serif",Font.BOLD,15));
        label3.setFont(new Font("serif",Font.BOLD,15));

        setLayout(null);

        c.add(label1);
        c.add(label2);
        c.add(label3);

        label1.setBounds(150,20,300,80);
        label2.setBounds(250,70,150,30);
        label3.setBounds(100,180,400,20);
    }

    public void actionPerformed(ActionEvent evt)
    {
        String getGame = evt.getActionCommand();

        if( getGame == "Unit Circle")
            cardlayout.show(c,"Unit Circle Game");

}

我至少要显示菜单/组合框和标签，而不是空白框。...