单击JMenu时如何显示JPanel？

Question

单击“ homeMenu”时，控制台上将显示“选择菜单”和“取消选择菜单”，而不会出现面板。单击“ homeMenu”时应如何使面板出现？

public class MyClass extends JApplet{
    JMenuBar menuBar;
    JMenu fileMenu, homeMenu;

    public MyClass () {
        setTheMenuBar();
    }

    void setTheMenuBar() {
        menuBar = new JMenuBar();
        setJMenuBar(menuBar);
        homeMenu = new JMenu("Home");
        menuBar.add(homeMenu);
        homeMenu.addMenuListener(new MenuListener() {
        @Override
        public void menuSelected(MenuEvent e) {
            JPanel p = new JPanel(new FlowLayout());
            p.add(new JButton("yara"));
            add(p, BorderLayout.NORTH);
            System.out.println("Menu selected");
        }

        @Override
        public void menuDeselected(MenuEvent e) {
            System.out.println("Menu deselected");
        }

        @Override
        public void menuCanceled(MenuEvent e) {
            System.out.println("Menu canceled");
        }
    });

       public static void main(String[] args) {
           // TODO code application logic here
           MyClass applet = new MyClass();
           JFrame frame = new JFrame();
           frame.add(applet);
           frame.setExtendedState(JFrame.MAXIMIZED_BOTH); 
           frame.setVisible(true);
           frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
           applet.start();
      }
}