Swing JMenu類

菜單類表示這是從菜單欄部署的下拉菜單組件。

類聲明

以下是聲明 javax.swing.JMenu類：

public class JMenu
   extends JMenuItem
      implements Accessible, MenuElement

字段域

以下是java.awt.Component類的字段：

protected JMenu.WinListener popupListener -- 監聽器的彈出窗口關閉。

類構造函數

S.N.	構造函數 & 描述
1	JMenu() Constructs a new JMenu with no text.
2	JMenu(Action a) Constructs a menu whose properties are taken from the Action supplied.
3	JMenu(String s) Constructs a new JMenu with the supplied string as its text.
4	JMenu(String s, boolean b) Constructs a new JMenu with the supplied string as its text and specified as a tear-off menu or not.

類方法

S.N.	方法 & 描述
1	JMenuItem add(Action a) Creates a new menu item attached to the specified Action object and appends it to the end of this menu.
2	Component add(Component c) Appends a component to the end of this menu.
3	Component add(Component c, int index) Adds the specified component to this container at the given position.
4	JMenuItem add(JMenuItem menuItem) Appends a menu item to the end of this menu.
5	JMenuItem add(String s) Creates a new menu item with the specified text and appends it to the end of this menu.
6	void addMenuListener(MenuListener l) Adds a listener for menu events.
7	void addSeparator() Appends a new separator to the end of the menu.
8	void applyComponentOrientation(ComponentOrientation o) Sets the ComponentOrientation property of this menu and all components contained within it.
9	protected PropertyChangeListener createActionChangeListener(JMenuItem b) Returns a properly configured PropertyChangeListener which updates the control as changes to the Action occur.
10	protected JMenuItem createActionComponent(Action a) Factory method which creates the JMenuItem for Actions added to the JMenu.
11	protected JMenu.WinListener createWinListener(JPopupMenu p) Creates a window-closing listener for the popup.
12	void doClick(int pressTime) Programmatically performs a "click".
13	protected void fireMenuCanceled() Notifies all listeners that have registered interest for notification on this event type.
14	protected void fireMenuDeselected() Notifies all listeners that have registered interest for notification on this event type.
15	protected void fireMenuSelected() Notifies all listeners that have registered interest for notification on this event type.
16	AccessibleContext getAccessibleContext() Gets the AccessibleContext associated with this JMenu.
17	Component getComponent() Returns the java.awt.Component used to paint this MenuElement.
18	int getDelay() Returns the suggested delay, in milliseconds, before submenus are popped up or down.
19	JMenuItem getItem(int pos) Returns the JMenuItem at the specified position.
20	int getItemCount() Returns the number of items on the menu, including separators.
21	Component getMenuComponent(int n) Returns the component at position n.
22	int getMenuComponentCount() Returns the number of components on the menu.
23	Component[] getMenuComponents() Returns an array of Components of the menu's subcomponents.
24	MenuListener[] getMenuListeners() Returns an array of all the MenuListeners added to this JMenu with addMenuListener().
25	JPopupMenu getPopupMenu() Returns the popupmenu associated with this menu.
26	protected Point getPopupMenuOrigin() Computes the origin for the JMenu's popup menu.
27	MenuElement[] getSubElements() Returns an array of MenuElements containing the submenu for this menu component.
28	String getUIClassID() Returns the name of the L&F class that renders this component.
29	JMenuItem insert(Action a, int pos) Inserts a new menu item attached to the specified Action object at a given position.
30	JMenuItem insert(JMenuItem mi, int pos) Inserts the specified JMenuitem at a given position.
31	void insert(String s, int pos) Inserts a new menu item with the specified text at a given position.
32	void insertSeparator(int index) Inserts a separator at the specified position.
33	boolean isMenuComponent(Component c) Returns true if the specified component exists in the submenu hierarchy.
34	boolean isPopupMenuVisible() Returns true if the menu's popup window is visible.
35	boolean isSelected() Returns true if the menu is currently selected (highlighted).
36	boolean isTearOff() Returns true if the menu can be torn off.
37	boolean isTopLevelMenu() Returns true if the menu is a 'top-level menu', that is, if it is the direct child of a menubar.
38	void menuSelectionChanged(boolean isIncluded) Messaged when the menubar selection changes to activate or deactivate this menu.
39	protected String paramString() Returns a string representation of this JMenu.
40	protected void processKeyEvent(KeyEvent evt) Processes key stroke events such as mnemonics and accelerators.
41	void remove(Component c) Removes the component c from this menu.
42	void remove(int pos) Removes the menu item at the specified index from this menu.
43	void remove(JMenuItem item) Removes the specified menu item from this menu.
44	void removeAll() Removes all menu items from this menu.
45	void removeMenuListener(MenuListener l) Removes a listener for menu events.
46	void setAccelerator(KeyStroke keyStroke) setAccelerator is not defined for JMenu.
47	void setComponentOrientation(ComponentOrientation o) Sets the language-sensitive orientation that is to be used to order the elements or text within this component.
48	void setDelay(int d) Sets the suggested delay before the menu's PopupMenu is popped up or down.
49	void setMenuLocation(int x, int y) Sets the location of the popup component.
50	void setModel(ButtonModel newModel) Sets the data model for the "menu button" -- the label that the user clicks to open or close the menu.
51	void setPopupMenuVisible(boolean b) Sets the visibility of the menu's popup.
52	void setSelected(boolean b) Sets the selection status of the menu.
53	void updateUI() Resets the UI property with a value from the current look and feel.

方法繼承

這個類從以下類繼承的方法：

javax.swing.JAbstractButton
javax.swing.JComponent
java.awt.Container
java.awt.Component
java.lang.Object

JMenu 例子

選擇使用任何編輯器創建以下java程序在 D:/ > SWING > com > yiibai > gui >

SwingMenuDemo.java

package com.yiibai.gui;

import java.awt.*;
import java.awt.event.*;

public class SwingMenuDemo {
   private JFrame mainFrame;
   private JLabel headerLabel;
   private JLabel statusLabel;
   private JPanel controlPanel; 

   public SwingMenuDemo(){
      prepareGUI();
   }

   public static void main(String[] args){
      SwingMenuDemo  swingMenuDemo = new SwingMenuDemo();     
      swingMenuDemo.showMenuDemo();
   }
   
   private void prepareGUI(){
      mainFrame = new JFrame("Java SWING Examples");
      mainFrame.setSize(400,400);
      mainFrame.setLayout(new GridLayout(3, 1));

      headerLabel = new JLabel("",JLabel.CENTER );
      statusLabel = new JLabel("",JLabel.CENTER);        

      statusLabel.setSize(350,100);
      mainFrame.addWindowListener(new WindowAdapter() {
         public void windowClosing(WindowEvent windowEvent){
            System.exit(0);
         }        
      });    
      controlPanel = new JPanel();
      controlPanel.setLayout(new FlowLayout());

      mainFrame.add(headerLabel);
      mainFrame.add(controlPanel);
      mainFrame.add(statusLabel);
      mainFrame.setVisible(true);  
   }

   private void showMenuDemo(){
      //create a menu bar
      final JMenuBar menuBar = new JMenuBar();

      //create menus
      JMenu fileMenu = new JMenu("File");
      JMenu editMenu = new JMenu("Edit"); 
      final JMenu aboutMenu = new JMenu("About");
      final JMenu linkMenu = new JMenu("Links");
     
      //create menu items
      JMenuItem newMenuItem = new JMenuItem("New");
      newMenuItem.setMnemonic(KeyEvent.VK_N);
      newMenuItem.setActionCommand("New");

      JMenuItem openMenuItem = new JMenuItem("Open");
      openMenuItem.setActionCommand("Open");

      JMenuItem saveMenuItem = new JMenuItem("Save");
      saveMenuItem.setActionCommand("Save");

      JMenuItem exitMenuItem = new JMenuItem("Exit");
      exitMenuItem.setActionCommand("Exit");

      JMenuItem cutMenuItem = new JMenuItem("Cut");
      cutMenuItem.setActionCommand("Cut");

      JMenuItem copyMenuItem = new JMenuItem("Copy");
      copyMenuItem.setActionCommand("Copy");

      JMenuItem pasteMenuItem = new JMenuItem("Paste");
      pasteMenuItem.setActionCommand("Paste");

      MenuItemListener menuItemListener = new MenuItemListener();

      newMenuItem.addActionListener(menuItemListener);
      openMenuItem.addActionListener(menuItemListener);
      saveMenuItem.addActionListener(menuItemListener);
      exitMenuItem.addActionListener(menuItemListener);
      cutMenuItem.addActionListener(menuItemListener);
      copyMenuItem.addActionListener(menuItemListener);
      pasteMenuItem.addActionListener(menuItemListener);

      final JCheckBoxMenuItem showWindowMenu = 
         new JCheckBoxMenuItem("Show About", true);
      showWindowMenu.addItemListener(new ItemListener() {
         public void itemStateChanged(ItemEvent e) {
            if(showWindowMenu.getState()){
               menuBar.add(aboutMenu);
            }else{
               menuBar.remove(aboutMenu);
            }
         }
      });

      final JRadioButtonMenuItem showLinksMenu = 
         new JRadioButtonMenuItem("Show Links", true);
      showLinksMenu.addItemListener(new ItemListener() {
         public void itemStateChanged(ItemEvent e) {
            if(menuBar.getMenu(3)!= null){
               menuBar.remove(linkMenu);
               mainFrame.repaint();
            }else{                   
               menuBar.add(linkMenu);
               mainFrame.repaint();
            }
         }
      });

      //add menu items to menus
      fileMenu.add(newMenuItem);
      fileMenu.add(openMenuItem);
      fileMenu.add(saveMenuItem);
      fileMenu.addSeparator();
      fileMenu.add(showWindowMenu);
      fileMenu.addSeparator();
      fileMenu.add(showLinksMenu);       
      fileMenu.addSeparator();
      fileMenu.add(exitMenuItem);        
      editMenu.add(cutMenuItem);
      editMenu.add(copyMenuItem);
      editMenu.add(pasteMenuItem);

      //add menu to menubar
      menuBar.add(fileMenu);
      menuBar.add(editMenu);
      menuBar.add(aboutMenu);       
      menuBar.add(linkMenu);

      //add menubar to the frame
      mainFrame.setJMenuBar(menuBar);
      mainFrame.setVisible(true);     
   }

   class MenuItemListener implements ActionListener {
      public void actionPerformed(ActionEvent e) {            
         statusLabel.setText(e.getActionCommand() 
         + " JMenuItem clicked.");
      }    
   }
}

編譯程序，使用命令提示符。到 D:/ > SWING 然後輸出以下命令。

D:SWING>javac comyiibaiguiSwingMenuDemo.java

如果冇有錯誤出現，這意味著編譯成功。使用下麵的命令來運行程序。

D:SWING>java com.yiibai.gui.SwingMenuDemo

驗證下麵的輸出。（點擊“File”菜單）