清华大学：JAVA教学课件：8-11

程序8-11：
import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
public class MenuDemo implements ItemListener,ActionListener{
JFrame frame = new JFrame ("Menu Demo");
JTextField tf = new JTextField();
public static void main(String args[]) {
MenuDemo menuDemo = new MenuDemo();
menuDemo.go();
}
public void go() {
JMenuBar menubar = new JMenuBar(); //菜单栏
frame.setJMenuBar(menubar);
JMenu menu,submenu; //菜单和子菜单
JMenuItem menuItem; //菜单项
// 建立File菜单
menu = new JMenu( "File");
menu.setMnemonic(KeyEvent.VK_F);
menubar.add(menu);

//File中的菜单项
menuItem = new JMenuItem( "Open..." );
menuItem.setMnemonic(KeyEvent.VK_O);//设置快捷键
menuItem.setAccelerator(KeyStroke.getKeyStroke(
KeyEvent.VK_1,ActionEvent.ALT_MASK)); //设置加速键
menuItem.addActionListener(this);
menu.add(menuItem);

menuItem = new JMenuItem( "Save",KeyEvent.VK_S );
menuItem.addActionListener(this);
menuItem.setEnabled(false);//设置为不可用
menu.add(menuItem);

menuItem = new JMenuItem( "Close" );
menuItem.setMnemonic(KeyEvent.VK_C);
menuItem.addActionListener(this);
menu.add(menuItem);

menu.add(new JSeparator());//加入分隔线

menuItem = new JMenuItem( "Exit" );
menuItem.setMnemonic(KeyEvent.VK_E);
menuItem.addActionListener(this);
menu.add(menuItem);

// 建立Option菜单
menu = new JMenu( "Option" );
menubar.add(menu);

//Option中的菜单项
menu.add( "Font..." );

// 建立子菜单
submenu = new JMenu("Color...");
menu.add(submenu);

menuItem = new JMenuItem( "Foreground" );
menuItem.addActionListener(this);
menuItem.setAccelerator(KeyStroke.getKeyStroke(
KeyEvent.VK_2,ActionEvent.ALT_MASK)); //设置加速键
submenu.add(menuItem);
menuItem = new JMenuItem( "Background" );
menuItem.addActionListener(this);
menuItem.setAccelerator(KeyStroke.getKeyStroke(
KeyEvent.VK_3,ActionEvent.ALT_MASK)); //设置加速键
submenu.add(menuItem);

menu.addSeparator();//加入分隔线
JCheckBoxMenuItem cm = new JCheckBoxMenuItem("Always On Top");
cm.addItemListener(this);
menu.add(cm);

menu.addSeparator();
JRadioButtonMenuItem rm = new JRadioButtonMenuItem("Small",true);
rm.addItemListener(this);
menu.add(rm);
ButtonGroup group = new ButtonGroup();
group.add(rm);

rm = new JRadioButtonMenuItem("Large");
rm.addItemListener(this);
menu.add(rm);
group.add(rm);

// 建立Help菜单
menu = new JMenu( "Help" );
menubar.add(menu);

menuItem = new JMenuItem( "about...",new ImageIcon("dukeWaveRed.gif"));
menuItem.addActionListener(this);
menu.add(menuItem);

tf.setEditable(false); //设置为不可编辑的

Container cp = frame.getContentPane();
cp.add(tf,BorderLayout.SOUTH);

frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.setSize(300,200);
frame.setVisible(true);
}

// 实现ItemListener接口中的方法
public void itemStateChanged(ItemEvent e) {
int state = e.getStateChange();
JMenuItem amenuItem = (JMenuItem)e.getSource();
String command = amenuItem.getText();
if (state==ItemEvent.SELECTED)
tf.setText(command+" SELECTED");
else
tf.setText(command+" DESELECTED");
}
// 实现ActionListener接口中的方法
public void actionPerformed(ActionEvent e) {
tf.setText(e.getActionCommand());
if (e.getActionCommand()=="Exit") {
System.exit(0);
}
}