java - JMenuBar不会出现在JFrame中

Question

我知道这个问题已经被问了很多次，但似乎没有什么对我有用，所以我会再问一次。我试图让一个带有 JMenu 的 JMenuBar 显示在扩展 JFrame 的 Window 类中。这是我的相关代码:

public class Window extends JFrame {
    //class variables
    JMenuBar menuBar;
    JMenu menu;

    Window() throws IOExcpetion {

    menuBar = new JMenuBar();
    menu = new JMenu("A Menu");
    menuBar.add(menu);
    this.setJMenuBar(menuBar);
    this.add(menuBar); //I've tried with and without this
    menu.setVisible(true);
    menuBar.setVisible(true);

    this.setVisible(true);

    while(true) {
        repaint(); //my paint method doesn't touch the JMenuBar or JMenu
    }
}

Answer 1

杀...

while(true) {
    repaint(); //my paint method doesn't touch the JMenuBar or JMenu
}

这会阻塞事件调度线程，使系统无法绘制任何东西......

还有...

menu.setVisible(true);
menuBar.setVisible(true);

Swing 组件默认是可见的，所以上面的内容毫无意义，我知道，您只是在抓面包屑，但您应该注意，这很少是问题

import java.awt.BorderLayout;
import java.awt.EventQueue;
import java.io.IOException;
import java.util.logging.Level;
import java.util.logging.Logger;
import javax.swing.JFrame;
import javax.swing.JMenu;
import javax.swing.JMenuBar;
import javax.swing.UIManager;
import javax.swing.UnsupportedLookAndFeelException;

public class TestWindow extends JFrame {

    //class variables
    JMenuBar menuBar;
    JMenu menu;

    TestWindow() throws IOException {

        menuBar = new JMenuBar();
        menu = new JMenu("A Menu");
        menuBar.add(menu);
        this.setJMenuBar(menuBar);
//        this.add(menuBar); //I've tried with and without this
//        menu.setVisible(true);
//        menuBar.setVisible(true);

        this.setVisible(true);

//        while (true) {
//            repaint(); //my paint method doesn't touch the JMenuBar or JMenu
//        }
    }

    public static void main(String[] args) {
        EventQueue.invokeLater(new Runnable() {
            @Override
            public void run() {
                try {
                    try {
                        UIManager.setLookAndFeel(UIManager.getSystemLookAndFeelClassName());
                    } catch (ClassNotFoundException | InstantiationException | IllegalAccessException | UnsupportedLookAndFeelException ex) {
                    }

                    TestWindow frame = new TestWindow();
                    frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
                    frame.pack();
                    frame.setLocationRelativeTo(null);
                    frame.setVisible(true);
                } catch (IOException ex) {
                    ex.printStackTrace();
                }
            }
        });
    }
}