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Java(TM) 2 Platform, Standard Edition, v1.2.2 API Specification: Class Menu - JDK 5 Documentation v1.2.2, Java 2 SDK 英文文档

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java.awt
Class Menu

java.lang.Object
  |
  +--java.awt.MenuComponent
        |
        +--java.awt.MenuItem
              |
              +--java.awt.Menu
Direct Known Subclasses:
PopupMenu
public class Menu
extends MenuItem
implements MenuContainer

A Menu object is a pull-down menu component that is deployed from a menu bar.

A menu can optionally be a tear-off menu. A tear-off menu can be opened and dragged away from its parent menu bar or menu. It remains on the screen after the mouse button has been released. The mechanism for tearing off a menu is platform dependent, since the look and feel of the tear-off menu is determined by its peer. On platforms that do not support tear-off menus, the tear-off property is ignored.

Each item in a menu must belong to the MenuItem class. It can be an instance of MenuItem, a submenu (an instance of Menu), or a check box (an instance of CheckboxMenuItem).

Since:
JDK1.0
See Also:
MenuItem, CheckboxMenuItem, Serialized Form

Constructor Summary
Menu()
          Constructs a new menu with an empty label.
Menu(String label)
          Constructs a new menu with the specified label.
Menu(String label, boolean tearOff)
          Constructs a new menu with the specified label, indicating whether the menu can be torn off.
 
Method Summary
 MenuItem add(MenuItem mi)
          Adds the specified menu item to this menu.
 void add(String label)
          Adds an item with the specified label to this menu.
 void addNotify()
          Creates the menu's peer.
 void addSeparator()
          Adds a separator line, or a hypen, to the menu at the current position.
 int countItems()
          Deprecated. As of JDK version 1.1, replaced by getItemCount().
 MenuItem getItem(int index)
          Gets the item located at the specified index of this menu.
 int getItemCount()
          Get the number of items in this menu.
 void insert(MenuItem menuitem, int index)
          Inserts a menu item into this menu at the specified position.
 void insert(String label, int index)
          Inserts a menu item with the specified label into this menu at the specified position.
 void insertSeparator(int index)
          Inserts a separator at the specified position.
 boolean isTearOff()
          Indicates whether this menu is a tear-off menu.
 String paramString()
          Gets the parameter string representing the state of this menu.
 void remove(int index)
          Removes the menu item at the specified index from this menu.
 void remove(MenuComponent item)
          Removes the specified menu item from this menu.
 void removeAll()
          Removes all items from this menu.
 void removeNotify()
          Removes the menu's peer.
 
Methods inherited from class java.awt.MenuItem
addActionListener, deleteShortcut, disable, disableEvents, enable, enable, enableEvents, getActionCommand, getLabel, getShortcut, isEnabled, processActionEvent, processEvent, removeActionListener, setActionCommand, setEnabled, setLabel, setShortcut
 
Methods inherited from class java.awt.MenuComponent
dispatchEvent, getFont, getName, getParent, getPeer, getTreeLock, postEvent, setFont, setName, toString
 
Methods inherited from class java.lang.Object
clone, equals, finalize, getClass, hashCode, notify, notifyAll, wait, wait, wait
 

Constructor Detail

Menu

public Menu()
Constructs a new menu with an empty label. This menu is not a tear-off menu.
Since:
JDK1.1

Menu

public Menu(String label)
Constructs a new menu with the specified label. This menu is not a tear-off menu.
Parameters:
label - the menu's label in the menu bar, or in another menu of which this menu is a submenu.

Menu

public Menu(String label,
            boolean tearOff)
Constructs a new menu with the specified label, indicating whether the menu can be torn off.

Tear-off functionality may not be supported by all implementations of AWT. If a particular implementation doesn't support tear-off menus, this value is silently ignored.

Parameters:
label - the menu's label in the menu bar, or in another menu of which this menu is a submenu.
tearOff - if true, the menu is a tear-off menu.
Since:
JDK1.0.
Method Detail

addNotify

public void addNotify()
Creates the menu's peer. The peer allows us to modify the appearance of the menu without changing its functionality.
Overrides:
addNotify in class MenuItem

removeNotify

public void removeNotify()
Removes the menu's peer. The peer allows us to modify the appearance of the menu without changing its functionality.
Overrides:
removeNotify in class MenuComponent

isTearOff

public boolean isTearOff()
Indicates whether this menu is a tear-off menu.

Tear-off functionality may not be supported by all implementations of AWT. If a particular implementation doesn't support tear-off menus, this value is silently ignored.

Returns:
true if this is a tear-off menu; false otherwise.

getItemCount

public int getItemCount()
Get the number of items in this menu.
Returns:
the number of items in this menu.
Since:
JDK1.1

countItems

public int countItems()
Deprecated. As of JDK version 1.1, replaced by getItemCount().

getItem

public MenuItem getItem(int index)
Gets the item located at the specified index of this menu.
Parameters:
index - the position of the item to be returned.
Returns:
the item located at the specified index.

add

public MenuItem add(MenuItem mi)
Adds the specified menu item to this menu. If the menu item has been part of another menu, remove it from that menu.
Parameters:
mi - the menu item to be added.
Returns:
the menu item added.
See Also:
insert(java.lang.String, int), insert(java.awt.MenuItem, int)

add

public void add(String label)
Adds an item with the specified label to this menu.
Parameters:
label - the text on the item.
See Also:
insert(java.lang.String, int), insert(java.awt.MenuItem, int)

insert

public void insert(MenuItem menuitem,
                   int index)
Inserts a menu item into this menu at the specified position.
Parameters:
menuitem - the menu item to be inserted.
index - the position at which the menu item should be inserted.
Throws:
IllegalArgumentException - if the value of index is less than zero.
Since:
JDK1.1
See Also:
add(java.lang.String), add(java.awt.MenuItem)

insert

public void insert(String label,
                   int index)
Inserts a menu item with the specified label into this menu at the specified position.
Parameters:
label - the text on the item.
index - the position at which the menu item should be inserted.
Since:
JDK1.1
See Also:
add(java.lang.String), add(java.awt.MenuItem)

addSeparator

public void addSeparator()
Adds a separator line, or a hypen, to the menu at the current position.
See Also:
insertSeparator(int)

insertSeparator

public void insertSeparator(int index)
Inserts a separator at the specified position.
Parameters:
index - the position at which the menu separator should be inserted.
Throws:
IllegalArgumentException - if the value of index is less than 0.
Since:
JDK1.1
See Also:
addSeparator()

remove

public void remove(int index)
Removes the menu item at the specified index from this menu.
Parameters:
index - the position of the item to be removed.

remove

public void remove(MenuComponent item)
Removes the specified menu item from this menu.
Specified by:
remove in interface MenuContainer
Parameters:
item - the item to be removed from the menu

removeAll

public void removeAll()
Removes all items from this menu.
Since:
JDK1.0.

paramString

public String paramString()
Gets the parameter string representing the state of this menu. This string is useful for debugging.
Overrides:
paramString in class MenuItem
Since:
JDK1.0nu.
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