java - 当我使用运行文件进行测试时，NetBeans GUI 设计表现不一致

Question

当我选择运行文件来测试我的代码时，GUI 应用程序的菜单栏不会始终出现。我使用的是 NetBeans IDE 版本 7.0.1。我通过选择代码中的任意位置，右键单击鼠标并从结果菜单中选择“运行文件”来测试代码。生成的 GUI 应用程序有菜单栏，但当我重新运行该应用程序时，菜单栏不存在，但当我重新运行它时，菜单栏出现。 或许你可以测试一下运行程序时是否也遇到同样的问题？在运行程序之前是否需要清除某种残留内存？代码如下:

public static void main(String[] args) {
    JFrame main = new JFrame("Main");
    main.setVisible(true);
    main.setSize(600, 600);
    main.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
    JPanel panel = new JPanel(new GridBagLayout());
    GridBagConstraints contraints = new GridBagConstraints();
    main.getContentPane().add(panel, BorderLayout.NORTH);
    contraints.gridx = 0;
    contraints.gridy = 0;
    contraints.insets = new Insets(0,0,0,0);

    //Adding labels and buttons
    JLabel enterUserName = new JLabel("Enter User Name:");
    contraints.gridx = 0;
    contraints.gridy = 1;
    contraints.insets = new Insets(1, 1, 1, 1);
    panel.add(enterUserName, contraints);
    JLabel enterPassWord = new JLabel("Enter Password:");
    contraints.gridx = 0;
    contraints.gridy = 2;
    contraints.insets = new Insets(1, 1, 1, 1);
    panel.add(enterPassWord, contraints);
    JButton logInButton = new JButton("Login");
    contraints.gridx = 0;
    contraints.gridy = 3;
    contraints.insets = new Insets(1, 1, 1, 1);
    panel.add(logInButton, contraints);
    logInButton.addActionListener(new helpAbout());


    //Adding menu bar and menubar items
    JMenuBar menuBar = new JMenuBar();
    main.setJMenuBar(menuBar);
    contraints.gridx = 0;
    contraints.gridy = 0;
    contraints.insets = new Insets(0, 0, 0, 0);
    JMenu file = new JMenu("File");
    menuBar.add(file, contraints);
    JMenu help = new JMenu("Help");
    menuBar.add(help, contraints);

    //Adding menu bar functionality
    JMenuItem exit = new JMenuItem("Exit");
    file.add(exit);
    exit.addActionListener(new fileExit());
    JMenuItem about = new JMenuItem("About");
    help.add(about);
    about.addActionListener(new helpAbout());
}

static class helpAbout implements ActionListener {

    @Override
    public void actionPerformed(ActionEvent e) {
        JFrame test = new JFrame("About");
        test.setVisible(true);
        test.setSize(200, 200);
        JLabel label2 = new JLabel("About");
        JPanel panel2 = new JPanel();
        test.add(panel2);
        panel2.add(label2);
    }
}

static class fileExit implements ActionListener {

    @Override
    public void actionPerformed(ActionEvent e) {
        System.exit(0);
    }
}

Answer 1

构建框架后调用setVisible(true)。

如果您将布局/控件添加到可见表单(您可能希望在其他情况下执行此操作)，则需要在框架/面板上调用 revalidate()。