没有出现Java菜单栏

Question

嘿，伙计们，我正试图从其他类制作一个菜单栏到我的JFrame，但它根本拒绝工作!I am on a deadend…

我真的不知道哪里出了问题，我试了一些其他的方法，但都不起作用。

The code is this :
  public Engine(int width, int height) {
    System.out.println("TEST ENGINE CLAASS");
    setTitle("Battleship Board - Place Your Ships");
    setSize(width, height);
    setLocation(624, 373);
    setDefaultCloseOperation(3);
    setResizable(false);
    setVisible(true);
    setLayout(null);
    System.out.println("TEST ENGINE clas2");
    Menu menu = new Menu(this);
    super.setJMenuBar(menu.getMenuBar());


    setDefaultCloseOperation(3);
}

public class Menu implements ActionListener {
    private Engine cc;
    private JMenuBar menuBar;
    private JMenu game;
    private JMenu help;
    private JMenuItem aboutItem;
    private JMenuItem quitItem;
    private JMenuItem newGameItem;
    public Menu (Engine cc) {
        System.out.println("testing menu class");
        this.cc = cc;
        this.menuBar = new JMenuBar();
        this.game = new JMenu("Game");
        this.help = new JMenu("Help");
        makeGameMenu();
        makeAboutMenu();

    }

   private void makeGameMenu() {
        System.out.println("Making game menu");
        this.newGameItem = new JMenuItem("New Game");
        this.game.add(this.newGameItem);
        this.newGameItem.addActionListener(this);
        this.game.addSeparator();
        this.quitItem.addActionListener(this);

        this.game.add(this.quitItem);
         this.menuBar.add(this.game);
    }
   private void makeAboutMenu() {
        this.aboutItem = new JMenuItem("About");
        this.help.add(aboutItem);
        this.menuBar.add(this.help);

    }
   public void actionPerformed(ActionEvent event) {
       JMenuItem source = (JMenuItem)event.getSource();
       //If user clicks new game then:
       if (source == this.newGameItem) {
           this.cc.newGame();
       }
       //If user clicks Quit then:
       else if (source == this.quitItem) {
           System.exit(0);
       }
       //If user clicks Help - About then:
       else if (source == this.aboutItem) {
           JOptionPane.showMessageDialog(null, "This Battleship Game was created by Manos Kontakis for Object Oriented Programming Lab", "About", 1);
       }
   }
   public JMenuBar getMenuBar()
  {
    return this.menuBar;
  }

}

Answer 1

JMenuItem quitItem没有在任何地方初始化，因此在JMenuBar可以添加到JFrame之前会抛出异常:

quitItem = new JMenuItem("Quit Game");
quitItem.addActionListener(...);

Aside:避免使用绝对定位(null布局)，始终使用布局管理器

Answer 2

我认为你必须从JMenuBar扩展并将组件添加到"this"