没有在java拆分窗格中添加菜单栏

Question

我写了一个小的测试程序，它创建了一个拆分窗格，其中一个窗格是文本区域。我已经在窗格中添加了一个meubar和菜单项，但在创建的gui中没有看到它们。

有人能指出我在下面的程序中做错了什么吗：

import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
import javax.swing.event.*;
import javax.swing.JMenuBar;
import java.util.*;
import javax.swing.text.BadLocationException;
import java.awt.*;
import java.io.IOException;

//SplitPaneDemo itself is not a visible component.
public class SplitPaneDemo extends JFrame
                          implements ActionListener {
    private JTextArea ta;
    private JMenuBar menuB;
        private JMenu dbM;
        private JMenuItem cnadb,bsmdb,cdmdb;
     private JLabel picture;

    private JSplitPane splitPane;
    public SplitPaneDemo() {
        ta = new JTextArea(); //textarea
        ta.setLineWrap(true);
            ta.setWrapStyleWord(true);
            ta.addKeyListener(new KeyAdapter()
        {
                 public void keyPressed(KeyEvent ke )
                 {
                 int code = ke.getKeyCode();
                 int modifiers = ke.getModifiers();
                 if(code == KeyEvent.VK_ENTER && modifiers == KeyEvent.CTRL_MASK)
                 {
                  System.out.println("cmd in table:");
           }
                }
                });
        JScrollPane taPane = new JScrollPane(ta);
        picture = new JLabel();
        picture.setFont(picture.getFont().deriveFont(Font.ITALIC));
        picture.setHorizontalAlignment(JLabel.CENTER);
        JScrollPane pictureScrollPane = new JScrollPane(picture);
        splitPane = new JSplitPane(JSplitPane.VERTICAL_SPLIT,
                                   taPane, pictureScrollPane);
        splitPane.setOneTouchExpandable(true);
        splitPane.setDividerLocation(450);
        //Provide minimum sizes for the two components in the split pane.
        Dimension minimumSize = new Dimension(100, 100);
        taPane.setMinimumSize(minimumSize);
        pictureScrollPane.setMinimumSize(minimumSize);
        //Provide a preferred size for the split pane.
        splitPane.setPreferredSize(new Dimension(900, 900));
              menuB = new JMenuBar(); //menubar
        dbM = new JMenu("DB"); //file menu
            cnadb = new JMenuItem("CNA");
            bsmdb = new JMenuItem("BSM");
            cdmdb = new JMenuItem("CDM");
            setJMenuBar(menuB);
            menuB.add(dbM);
            dbM.add(cnadb);
            dbM.add(bsmdb);
            dbM.add(cdmdb);
            cnadb.addActionListener(this);
            bsmdb.addActionListener(this);
            cdmdb.addActionListener(this);
            setVisible(true);
    }
        public void actionPerformed(ActionEvent e) 
        {
    }
    public void valueChanged(ListSelectionEvent e) {
    }
    public JSplitPane getSplitPane() {
        return splitPane;
    }

    private static void createAndShowGUI() {
        //Create and set up the window.
        JFrame frame = new JFrame("SplitPaneDemo");
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        SplitPaneDemo splitPaneDemo = new SplitPaneDemo();
        frame.getContentPane().add(splitPaneDemo.getSplitPane());
        //Display the window.
        frame.pack();
        frame.setVisible(true);
    }
    public static void main(String[] args) {
        //Schedule a job for the event-dispatching thread:
        //creating and showing this application's GUI.
        javax.swing.SwingUtilities.invokeLater(new Runnable() {
            public void run() {
                createAndShowGUI();
            }
        });
    }

}

Answer 1

您在SplitPaneDemo类中添加了JMenuBar，但当您实际调用createAndShowGUI时，您会生成一个新的JFrame，并通过调用getSplitPane将SplitPane添加到其中。这个新框架对菜单栏一无所知。

如果您在SplitPaneDemo中扩展JFrame，为什么不使用它为您的gui制作框架呢？