java - 为什么它不显示我的按钮？

Question

我正在尝试使用分层 Pane 为我正在处理的程序制作菜单，但该按钮不会显示。我似乎无法弄清楚它是什么......

public class FlashcardGUI {

public static void main(String[] args) 
{
    JFrame projectFrame = new JFrame("StudyFast Flashcard");
    projectFrame.setName("StudyFast Flashcards");
    projectFrame.setSize(1000,600);
    projectFrame.setDefaultCloseOperation(JFrame.DISPOSE_ON_CLOSE);
    projectFrame.setVisible(true);


    JLayeredPane projectLayeredPane = new JLayeredPane();
    projectFrame.setContentPane(projectLayeredPane);

    JPanel projectMenu1 = new JPanel();
    projectLayeredPane.setLayer(projectMenu1, 0);

    final JButton startNow = new JButton();
    startNow.setText("Exit");
    startNow.addActionListener(new ActionListener() 
        {
            public void actionPerformed(ActionEvent e) 
                {
                    System.exit(0);
                }
        });



    projectFrame.add(projectLayeredPane);
    projectLayeredPane.add(projectMenu1);
    projectMenu1.add(startNow);
    }
}

Answer 1

将这两行放在 main 方法的末尾。为了使按钮显示，顺序很重要。

projectFrame.pack();
projectFrame.setVisible(true);

(确保删除第 9 行中已有的 projectFrame.setVisible(true);。)