为什么即使在添加setJMenubar（）方法后Jombubar在我的Jframe中也不可见？ [重复]

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I am new to java swing class and was learning how to add menubars and menus in JFrame.

我是java swing类的新手,正在学习如何在JFrame中添加菜单栏和菜单。

I have written a simple example but the JFrame is displayed empty and I don't know why because I have included setJMenuBar() method in my code then also menubar isn't visible.

我写了一个简单的例子,但JFrame显示为空,我不知道为什么因为我在我的代码中包含了setJMenuBar()方法,所以菜单栏也不可见。

Here is my code

这是我的代码

import java.awt.*;
import javax.swing.*;
import java.awt.event.*;
public class jmenuexample extends JFrame //implements ActionListener
{
    JLabel title;
    JMenuBar menubar;
    JMenu menu, submenu;
    JMenuItem menuItem;
    jmenuexample()
    {
        setTitle("JMenu Example");
        setSize(750, 450);
        //setLayout(null);
        setVisible(true);
        setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        menubar = new JMenuBar();
        menu = new JMenu("File");
        menuItem = new JMenuItem("New\tCtrl+N");
        menu.add(menuItem);
        menuItem = new JMenuItem("Open\tCtrl+O");
        menu.add(menuItem);
        menuItem = new JMenuItem("Save\tCtrl+S");
        menu.add(menuItem);
        //menu.addSeparator();
        menuItem = new JMenuItem("Exit");
        menu.add(menuItem);
        menubar.add(menu);
        /*panel = new JPanel();
        panel.setLayout(new GridLayout());
        panel.setBounds(250,10, 400, 300);*/
        //add(menubar);
        //add(panel);
        this.setJMenuBar(menubar);
    }
    public static void main(String argv[])
    {
        new jmenuexample();
    }
}

And here is the output of this code.

以下是此代码的输出。

1 个解决方案

#1

Because you are using setVisible(true); before you set this.setJMenuBar(menubar);

因为你正在使用setVisible(true);在设置this.setJMenuBar(menubar)之前;

so chnage the order and setVisible(true); in the end.

所以chnage的顺序和setVisible(true);到底。

Your code should be like this:

你的代码应该是这样的:

....
menubar.add(menu);
/*panel = new JPanel();
 panel.setLayout(new GridLayout());
 panel.setBounds(250,10, 400, 300);*/
//add(menubar);
//add(panel);
this.setJMenuBar(menubar);
setVisible(true);
....

Hope this can help you.

希望这可以帮到你。

#1