Question

我的代码存在问题，似乎JComboBox会随时出现并消失。我有JComboBox何时工作的实例，然后关闭并重新启动程序会导致它再次停止工作。发生了什么事？

class FutoshikiGUI extends JFrame {
    JPanel main = new JPanel();
    public FutoshikiGUI() {
        super("Futoshiki");

        //setup standard GUI parameters
        setDefaultCloseOperation(EXIT_ON_CLOSE);
        setVisible(true);
        setResizable(false);
        setSize(600,600);
        add(main);

        //initialise other GUI components
        initPanel();
    }

    private void initPanel() {
        //prepare main panel
        main.setLayout(new GridBagLayout());
        main.setBackground(Color.decode("#FFFFFF"));

        //create and prepare title
        GridBagConstraints gbc = new GridBagConstraints();
        gbc.gridx = 0;
        gbc.gridy = 0;
        JLabel title = new JLabel("Futoshiki");
        title.setFont(new Font("Tahoma", Font.PLAIN, 20));
        main.add(title, gbc);

        //create and prepare combobox
        gbc.gridy = 1;
        String[] diff = {"Easy", "Med", "Hard"};
        JComboBox difficulty = new JComboBox(diff);
        difficulty.setSelectedIndex(0);
        main.add(difficulty);
    }

Answer 1

只有将所有组件添加到setVisible(true)后，才应致电JFrame。

另外，请在add(main)之后致电initPanel()，以确保JPanel也准备就绪：

public FutoshikiGUI() {
    super("Futoshiki");

    //setup standard GUI parameters
    setDefaultCloseOperation(EXIT_ON_CLOSE);


    //initialise other GUI components
    initPanel();

    add(main);

    setResizable(false);
    setSize(600,600);

    setVisible(true);
}

JComboBox不会出现。我究竟做错了什么？

1 个答案: