Java Swing JMenuBar

Question

我的JMenuBar没有全部显示.这只是一个准系统GUI.我现在坐在这里已经有一段时间了,我看不出问题所以,正如他们所说的那样,四只眼睛好于两只眼睛.

谢谢.

import javax.swing.*;
import java.awt.*;

public class MainGui{
    private DrawPanel drawPanel;
    private JFrame mainFrame;
    private JPanel drawPanel;
    private JMenuBar menuBar;
    private JMenu fileMenu, imgMenu, helpMenu;
    private JMenuItem fileNew, fileOpen, fileSave, fileExit;
    private JMenuItem imgBtn1;
    private JMenuItem hlpAbout;

    public MainGui(DrawPanel drawPanel){
    mainFrame = new JFrame("JDraw v1");
    mainFrame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
    mainFrame.setLayout(new BorderLayout());

    this.drawPanel = drawPanel;

    menuBar = new JMenuBar();
    fileMenu = new JMenu("File");
    imgMenu = new JMenu("Image");
    helpMenu = new JMenu("Help");

    fileNew = new JMenuItem("New File");
    fileOpen = new JMenuItem("Open File");
    fileSave = new JMenuItem("Save File");
    fileExit = new JMenuItem("Exit");
    imgBtn1 = new JMenuItem("Useless Button");
    hlpAbout = new JMenuItem("About this program");

    mainFrame.add(menuBar, BorderLayout.PAGE_START);
    menuBar.add(fileMenu);
    menuBar.add(imgMenu);
    menuBar.add(hlpMenu);

    fileMenu.add(fileNew);
    fileMenu.add(fileOpen);
    fileMenu.add(fileSave);
    fileMenu.add(fileExit);
    imgMenu.add(imgBtn1);
    helpMenu.add(hlpAbout);

    mainFrame.add(drawPanel, BorderLayout.CENTER);

    mainFrame.pack();
    mainFrame.setSize(640,480);
    mainFrame.setResizable(false);
    mainFrame.setVisible(true);
    }
}

Answer 1

你想做:

mainFrame.setJMenuBar(menuBar);

不:

mainFrame.add(menuBar, BorderLayout.PAGE_START);