好奇怪！好郁闷啊！JMenu的下拉菜单弹不出来

Question

各位同仁，一个奇快的问题发生在如下程序中，现请高人指点：
问题是：file菜单可以弹出下拉菜单，但是无法点击下拉菜单中的选项；edit菜单弹不出下拉菜单。本程序编辑、运行无误！
/**
 * 
 *//**
 * @author [email protected]
 *
 */
import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
import javax.swing.event.*;
public class JMenuTest  { /**
 * 定义控件
 */
JFrame frm=null;
JTextArea txta=null;
JMenu menuFile=null,menuEdit=null,openmenu=null;
JMenuItem open=null,close=null,exit=null,save=null,newf=null,openOld=null,openNew=null,copy=null,paste=null,cut=null;

public JMenuTest() {
// TODO Auto-generated constructor stub
/*
 * 构造函数，初始化
 */
frm=new JFrame("JMenu Test");
Container cp=frm.getContentPane();
JMenuBar  menuBar=new JMenuBar();
frm.setJMenuBar(menuBar);

menuFile=new JMenu("file");
menuEdit=new JMenu("Edit");

menuBar.add(menuFile);
menuBar.add(menuEdit);

open=new JMenuItem("open File",'O');//设置快捷键为'O'
//open.setMnemonic('O');//设置快捷键为'O'方法二
open.setAccelerator(KeyStroke.getKeyStroke(KeyEvent.VK_O,InputEvent.ALT_MASK));//设置快捷键‘O’，屏蔽ALT键
open.setIcon(new ImageIcon("2.gif"));//添加图标
newf=new JMenuItem("new File");
newf.setAccelerator(KeyStroke.getKeyStroke(KeyEvent.VK_N,InputEvent.ALT_MASK));
newf.setIcon(new ImageIcon("4.gif"));
save =new JMenuItem("save File");
save.setAccelerator(KeyStroke.getKeyStroke(KeyEvent.VK_S,InputEvent.ALT_MASK));
save.setIcon(new ImageIcon("6.gif"));
close =new JMenuItem("close");
close.setAccelerator(KeyStroke.getKeyStroke(KeyEvent.VK_L,InputEvent.ALT_MASK));
exit=new JMenuItem("exit");
exit.setAccelerator(KeyStroke.getKeyStroke(KeyEvent.VK_X,InputEvent.ALT_MASK));
menuFile.add(open);
menuFile.add(newf);
menuFile.add(save);
menuFile.add(close);
menuFile.addSeparator();
menuFile.add(exit);
openmenu=new JMenu();
openOld =new JMenuItem("openOld");
openNew =new JMenuItem("openNew");
openmenu.add(openOld);
openmenu.add(openNew);
open.add(openmenu);

menuEdit=new JMenu("Edit");
copy=new JMenuItem("copy");
paste=new JMenuItem("paste");
cut=new JMenuItem("cut");
menuEdit.add(copy);
menuEdit.add(paste);
menuEdit.add(cut);

/*
 * 注册菜单的事件
 */
open.addActionListener(new ItemActionLis());
close.addActionListener(new ItemActionLis());
exit.addActionListener(new ItemActionLis());
save.addActionListener(new ItemActionLis());
newf.addActionListener(new ItemActionLis());
copy.addActionListener(new ItemActionLis());
openOld.addActionListener(new ItemActionLis());
openNew.addActionListener(new ItemActionLis());
paste.addActionListener(new ItemActionLis());
cut.addActionListener(new ItemActionLis());
txta=new JTextArea();
cp.add(txta);

frm.setBounds(300,300,500,400);
frm.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frm.setVisible(true);
}
class ItemActionLis implements ActionListener
{
public void actionPerformed(ActionEvent ex)
{
if((JMenuItem)ex.getSource()==open)
{
txta.setText("你点击了打开菜单");
}
else if((JMenuItem)ex.getSource()==openOld)
{
txta.setText("你点击了打开旧菜单");
}
else if((JMenuItem)ex.getSource()==openNew)
{
txta.setText("你点击了打开新菜单");
}
else if((JMenuItem)ex.getSource()==save)
{
txta.setText("你点击了保存菜单");
}
else if((JMenuItem)ex.getSource()==close)
{
txta.setText("你点击了关闭菜单");
}
else if((JMenuItem)ex.getSource()==exit)
{
txta.setText("你点击了退出菜单");
}
else if((JMenuItem)ex.getSource()==newf)
{
txta.setText("你点击了新建菜单");
}
else if((JMenuItem)ex.getSource()==copy)
{
txta.setText("你点击的是复制菜单");
}
else if((JMenuItem)ex.getSource()==cut)
{
txta.setText("你点击的是剪切菜单");
}
else if((JMenuItem)ex.getSource()==paste)
{
txta.setText("你点击的是粘贴菜单");
}
}

} /**
 * @param args
 */
public static void main(String[] args) {
// TODO Auto-generated method stub
new JMenuTest(); }}

Answer 1

有两个menuEdit=new JMenu("Edit");把第二个删掉
就可以了

Answer 2

open=new JMenuItem("open File",'O');//设置快捷键为'O'
open.add(openmenu);
你的open是一个JMenuItem怎么能添加JMenu?还有
menuBar.add(menuFile);
menuBar.add(menuEdit);
调用得太早,应该在创建完菜单后再调用

Answer 3

怎样在菜单中套菜单呢？比如说打开IE中的“文件”－》“新建”－》“窗口”
--------------------JMenu fileMenu = new JMenu("文件"); //一级菜单
JMenu newMenu = new JMenu("新建"); //二级菜单
JMenuItem winMenuItem = new JMenuItem("窗口"); //注意：作后是菜单项JMenuItem
fileMenu.add(newMenu);
newMenu.add(winMenuItem);
winMenuItem.addActionListener(new ActionListener() {
   public void actionPerformed(ActionEvent e) {
         //事件处理代码....
   }
});