public class

JMenu

extends JMenuItem
implements Accessible MenuElement
java.lang.Object
   ↳ java.awt.Component
     ↳ java.awt.Container
       ↳ javax.swing.JComponent
         ↳ javax.swing.AbstractButton
           ↳ javax.swing.JMenuItem
             ↳ javax.swing.JMenu

Class Overview

An implementation of a menu -- a popup window containing JMenuItems that is displayed when the user selects an item on the JMenuBar. In addition to JMenuItems, a JMenu can also contain JSeparators.

In essence, a menu is a button with an associated JPopupMenu. When the "button" is pressed, the JPopupMenu appears. If the "button" is on the JMenuBar, the menu is a top-level window. If the "button" is another menu item, then the JPopupMenu is "pull-right" menu.

Menus can be configured, and to some degree controlled, by Actions. Using an Action with a menu has many benefits beyond directly configuring a menu. Refer to Swing Components Supporting Action for more details, and you can find more information in How to Use Actions, a section in The Java Tutorial.

For information and examples of using menus see How to Use Menus, a section in The Java Tutorial.

Warning: Swing is not thread safe. For more information see Swing's Threading Policy.

Warning: Serialized objects of this class will not be compatible with future Swing releases. The current serialization support is appropriate for short term storage or RMI between applications running the same version of Swing. As of 1.4, support for long term storage of all JavaBeansTM has been added to the java.beans package. Please see XMLEncoder.

Summary

Nested Classes
class JMenu.AccessibleJMenu This class implements accessibility support for the JMenu class. 
class JMenu.WinListener A listener class that watches for a popup window closing. 
[Expand]
Inherited Constants
From class javax.swing.AbstractButton
From class javax.swing.JComponent
From class java.awt.Component
From interface java.awt.image.ImageObserver
From interface javax.swing.SwingConstants
Fields
protected JMenu.WinListener popupListener The window-closing listener for the popup.
[Expand]
Inherited Fields
From class javax.swing.AbstractButton
From class javax.swing.JComponent
Public Constructors
JMenu()
Constructs a new JMenu with no text.
JMenu(String s)
Constructs a new JMenu with the supplied string as its text.
JMenu(Action a)
Constructs a menu whose properties are taken from the Action supplied.
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.
Public Methods
Component add(Component c, int index)
Adds the specified component to this container at the given position.
JMenuItem add(JMenuItem menuItem)
Appends a menu item to the end of this menu.
Component add(Component c)
Appends a component to the end of this menu.
JMenuItem add(Action a)
Creates a new menu item attached to the specified Action object and appends it to the end of this menu.
JMenuItem add(String s)
Creates a new menu item with the specified text and appends it to the end of this menu.
void addMenuListener(MenuListener l)
Adds a listener for menu events.
void addSeparator()
Appends a new separator to the end of the menu.
void applyComponentOrientation(ComponentOrientation o)
Sets the ComponentOrientation property of this menu and all components contained within it.
void doClick(int pressTime)
Programmatically performs a "click".
AccessibleContext getAccessibleContext()
Gets the AccessibleContext associated with this JMenu.
Component getComponent()
Returns the java.awt.Component used to paint this MenuElement.
int getDelay()
Returns the suggested delay, in milliseconds, before submenus are popped up or down.
JMenuItem getItem(int pos)
Returns the JMenuItem at the specified position.
int getItemCount()
Returns the number of items on the menu, including separators.
Component getMenuComponent(int n)
Returns the component at position n.
int getMenuComponentCount()
Returns the number of components on the menu.
Component[] getMenuComponents()
Returns an array of Components of the menu's subcomponents.
MenuListener[] getMenuListeners()
Returns an array of all the MenuListeners added to this JMenu with addMenuListener().
JPopupMenu getPopupMenu()
Returns the popupmenu associated with this menu.
MenuElement[] getSubElements()
Returns an array of MenuElements containing the submenu for this menu component.
String getUIClassID()
Returns the name of the L&F class that renders this component.
JMenuItem insert(Action a, int pos)
Inserts a new menu item attached to the specified Action object at a given position.
void insert(String s, int pos)
Inserts a new menu item with the specified text at a given position.
JMenuItem insert(JMenuItem mi, int pos)
Inserts the specified JMenuitem at a given position.
void insertSeparator(int index)
Inserts a separator at the specified position.
boolean isMenuComponent(Component c)
Returns true if the specified component exists in the submenu hierarchy.
boolean isPopupMenuVisible()
Returns true if the menu's popup window is visible.
boolean isSelected()
Returns true if the menu is currently selected (highlighted).
boolean isTearOff()
Returns true if the menu can be torn off.
boolean isTopLevelMenu()
Returns true if the menu is a 'top-level menu', that is, if it is the direct child of a menubar.
void menuSelectionChanged(boolean isIncluded)
Messaged when the menubar selection changes to activate or deactivate this menu.
void remove(JMenuItem item)
Removes the specified menu item from this menu.
void remove(Component c)
Removes the component c from this menu.
void remove(int pos)
Removes the menu item at the specified index from this menu.
void removeAll()
Removes all menu items from this menu.
void removeMenuListener(MenuListener l)
Removes a listener for menu events.
void setAccelerator(KeyStroke keyStroke)
setAccelerator is not defined for JMenu.
void setComponentOrientation(ComponentOrientation o)
Sets the language-sensitive orientation that is to be used to order the elements or text within this component.
void setDelay(int d)
Sets the suggested delay before the menu's PopupMenu is popped up or down.
void setMenuLocation(int x, int y)
Sets the location of the popup component.
void setModel(ButtonModel newModel)
Sets the data model for the "menu button" -- the label that the user clicks to open or close the menu.
void setPopupMenuVisible(boolean b)
Sets the visibility of the menu's popup.
void setSelected(boolean b)
Sets the selection status of the menu.
void updateUI()
Resets the UI property with a value from the current look and feel.
Protected Methods
PropertyChangeListener createActionChangeListener(JMenuItem b)
Returns a properly configured PropertyChangeListener which updates the control as changes to the Action occur.
JMenuItem createActionComponent(Action a)
Factory method which creates the JMenuItem for Actions added to the JMenu.
JMenu.WinListener createWinListener(JPopupMenu p)
Creates a window-closing listener for the popup.
void fireMenuCanceled()
Notifies all listeners that have registered interest for notification on this event type.
void fireMenuDeselected()
Notifies all listeners that have registered interest for notification on this event type.
void fireMenuSelected()
Notifies all listeners that have registered interest for notification on this event type.
Point getPopupMenuOrigin()
Computes the origin for the JMenu's popup menu.
String paramString()
Returns a string representation of this JMenu.
void processKeyEvent(KeyEvent evt)
Processes key stroke events such as mnemonics and accelerators.
[Expand]
Inherited Methods
From class javax.swing.JMenuItem
From class javax.swing.AbstractButton
From class javax.swing.JComponent
From class java.awt.Container
From class java.awt.Component
From class java.lang.Object
From interface java.awt.ItemSelectable
From interface java.awt.MenuContainer
From interface java.awt.image.ImageObserver
From interface javax.accessibility.Accessible
From interface javax.swing.MenuElement

Fields

protected JMenu.WinListener popupListener

The window-closing listener for the popup.

Public Constructors

public JMenu ()

Constructs a new JMenu with no text.

public JMenu (String s)

Constructs a new JMenu with the supplied string as its text.

Parameters
s the text for the menu label

public JMenu (Action a)

Constructs a menu whose properties are taken from the Action supplied.

Parameters
a an Action

public 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.

Parameters
s the text for the menu label
b can the menu be torn off (not yet implemented)

Public Methods

public Component add (Component c, int index)

Adds the specified component to this container at the given position. If index equals -1, the component will be appended to the end.

Parameters
c the Component to add
index the position at which to insert the component
Returns
  • the Component added

public JMenuItem add (JMenuItem menuItem)

Appends a menu item to the end of this menu. Returns the menu item added.

Parameters
menuItem the JMenuitem to be added
Returns
  • the JMenuItem added

public Component add (Component c)

Appends a component to the end of this menu. Returns the component added.

Parameters
c the Component to add
Returns
  • the Component added

public JMenuItem add (Action a)

Creates a new menu item attached to the specified Action object and appends it to the end of this menu.

Parameters
a the Action for the menu item to be added
See Also

public JMenuItem add (String s)

Creates a new menu item with the specified text and appends it to the end of this menu.

Parameters
s the string for the menu item to be added

public void addMenuListener (MenuListener l)

Adds a listener for menu events.

Parameters
l the listener to be added

public void addSeparator ()

Appends a new separator to the end of the menu.

public void applyComponentOrientation (ComponentOrientation o)

Sets the ComponentOrientation property of this menu and all components contained within it. This includes all components returned by getMenuComponents.

Parameters
o the new component orientation of this menu and the components contained within it.
Throws
NullPointerException if orientation is null.

public void doClick (int pressTime)

Programmatically performs a "click". This overrides the method AbstractButton.doClick in order to make the menu pop up.

Parameters
pressTime indicates the number of milliseconds the button was pressed for

public AccessibleContext getAccessibleContext ()

Gets the AccessibleContext associated with this JMenu. For JMenus, the AccessibleContext takes the form of an AccessibleJMenu. A new AccessibleJMenu instance is created if necessary.

Returns
  • an AccessibleJMenu that serves as the AccessibleContext of this JMenu

public Component getComponent ()

Returns the java.awt.Component used to paint this MenuElement. The returned component is used to convert events and detect if an event is inside a menu component.

Returns
  • the Component that paints this menu item

public int getDelay ()

Returns the suggested delay, in milliseconds, before submenus are popped up or down. Each look and feel (L&F) may determine its own policy for observing the delay property. In most cases, the delay is not observed for top level menus or while dragging. The default for delay is 0. This method is a property of the look and feel code and is used to manage the idiosyncracies of the various UI implementations.

Returns
  • the delay property

public JMenuItem getItem (int pos)

Returns the JMenuItem at the specified position. If the component at pos is not a menu item, null is returned. This method is included for AWT compatibility.

Parameters
pos an integer specifying the position
Returns
  • the menu item at the specified position; or null if the item as the specified position is not a menu item
Throws
IllegalArgumentException if the value of pos < 0

public int getItemCount ()

Returns the number of items on the menu, including separators. This method is included for AWT compatibility.

Returns
  • an integer equal to the number of items on the menu

public Component getMenuComponent (int n)

Returns the component at position n.

Parameters
n the position of the component to be returned
Returns
  • the component requested, or null if there is no popup menu

public int getMenuComponentCount ()

Returns the number of components on the menu.

Returns
  • an integer containing the number of components on the menu

public Component[] getMenuComponents ()

Returns an array of Components of the menu's subcomponents. Note that this returns all Components in the popup menu, including separators.

Returns
  • an array of Components or an empty array if there is no popup menu

public MenuListener[] getMenuListeners ()

Returns an array of all the MenuListeners added to this JMenu with addMenuListener().

Returns
  • all of the MenuListeners added or an empty array if no listeners have been added

public JPopupMenu getPopupMenu ()

Returns the popupmenu associated with this menu. If there is no popupmenu, it will create one.

public MenuElement[] getSubElements ()

Returns an array of MenuElements containing the submenu for this menu component. If popup menu is null returns an empty array. This method is required to conform to the MenuElement interface. Note that since JSeparators do not conform to the MenuElement interface, this array will only contain JMenuItems.

Returns
  • an array of MenuElement objects

public String getUIClassID ()

Returns the name of the L&F class that renders this component.

Returns
  • the string "MenuUI"

public JMenuItem insert (Action a, int pos)

Inserts a new menu item attached to the specified Action object at a given position.

Parameters
a the Action object for the menu item to add
pos an integer specifying the position at which to add the new menu item
Throws
IllegalArgumentException if the value of pos < 0

public void insert (String s, int pos)

Inserts a new menu item with the specified text at a given position.

Parameters
s the text for the menu item to add
pos an integer specifying the position at which to add the new menu item
Throws
IllegalArgumentException when the value of pos < 0

public JMenuItem insert (JMenuItem mi, int pos)

Inserts the specified JMenuitem at a given position.

Parameters
mi the JMenuitem to add
pos an integer specifying the position at which to add the new JMenuitem
Returns
  • the new menu item
Throws
IllegalArgumentException if the value of pos < 0

public void insertSeparator (int index)

Inserts a separator at the specified position.

Parameters
index an integer specifying the position at which to insert the menu separator
Throws
IllegalArgumentException if the value of index < 0

public boolean isMenuComponent (Component c)

Returns true if the specified component exists in the submenu hierarchy.

Parameters
c the Component to be tested
Returns
  • true if the Component exists, false otherwise

public boolean isPopupMenuVisible ()

Returns true if the menu's popup window is visible.

Returns
  • true if the menu is visible, else false

public boolean isSelected ()

Returns true if the menu is currently selected (highlighted).

Returns
  • true if the menu is selected, else false

public boolean isTearOff ()

Returns true if the menu can be torn off. This method is not yet implemented.

Returns
  • true if the menu can be torn off, else false
Throws
Error if invoked -- this method is not yet implemented

public boolean isTopLevelMenu ()

Returns true if the menu is a 'top-level menu', that is, if it is the direct child of a menubar.

Returns
  • true if the menu is activated from the menu bar; false if the menu is activated from a menu item on another menu

public void menuSelectionChanged (boolean isIncluded)

Messaged when the menubar selection changes to activate or deactivate this menu. Overrides JMenuItem.menuSelectionChanged.

Parameters
isIncluded true if this menu is active, false if it is not

public void remove (JMenuItem item)

Removes the specified menu item from this menu. If there is no popup menu, this method will have no effect.

Parameters
item the JMenuItem to be removed from the menu

public void remove (Component c)

Removes the component c from this menu.

Parameters
c the component to be removed

public void remove (int pos)

Removes the menu item at the specified index from this menu.

Parameters
pos the position of the item to be removed
Throws
IllegalArgumentException if the value of pos < 0, or if pos is greater than the number of menu items

public void removeAll ()

Removes all menu items from this menu.

public void removeMenuListener (MenuListener l)

Removes a listener for menu events.

Parameters
l the listener to be removed

public void setAccelerator (KeyStroke keyStroke)

setAccelerator is not defined for JMenu. Use setMnemonic instead.

Parameters
keyStroke the keystroke combination which will invoke the JMenuItem's actionlisteners without navigating the menu hierarchy
Throws
Error if invoked -- this method is not defined for JMenu. Use setMnemonic instead

public void setComponentOrientation (ComponentOrientation o)

Sets the language-sensitive orientation that is to be used to order the elements or text within this component. Language-sensitive LayoutManager and Component subclasses will use this property to determine how to lay out and draw components.

At construction time, a component's orientation is set to ComponentOrientation.UNKNOWN, indicating that it has not been specified explicitly. The UNKNOWN orientation behaves the same as ComponentOrientation.LEFT_TO_RIGHT.

To set the orientation of a single component, use this method. To set the orientation of an entire component hierarchy, use applyComponentOrientation.

public void setDelay (int d)

Sets the suggested delay before the menu's PopupMenu is popped up or down. Each look and feel (L&F) may determine it's own policy for observing the delay property. In most cases, the delay is not observed for top level menus or while dragging. This method is a property of the look and feel code and is used to manage the idiosyncracies of the various UI implementations.

Parameters
d the number of milliseconds to delay
Throws
IllegalArgumentException if d is less than 0

public void setMenuLocation (int x, int y)

Sets the location of the popup component.

Parameters
x the x coordinate of the popup's new position
y the y coordinate of the popup's new position

public void setModel (ButtonModel newModel)

Sets the data model for the "menu button" -- the label that the user clicks to open or close the menu.

Parameters
newModel the ButtonModel
See Also

public void setPopupMenuVisible (boolean b)

Sets the visibility of the menu's popup. If the menu is not enabled, this method will have no effect.

Parameters
b a boolean value -- true to make the menu visible, false to hide it

public void setSelected (boolean b)

Sets the selection status of the menu.

Parameters
b true to select (highlight) the menu; false to de-select the menu

public void updateUI ()

Resets the UI property with a value from the current look and feel.

See Also

Protected Methods

protected PropertyChangeListener createActionChangeListener (JMenuItem b)

Returns a properly configured PropertyChangeListener which updates the control as changes to the Action occur.

protected JMenuItem createActionComponent (Action a)

Factory method which creates the JMenuItem for Actions added to the JMenu.

Parameters
a the Action for the menu item to be added
Returns
  • the new menu item
See Also

protected JMenu.WinListener createWinListener (JPopupMenu p)

Creates a window-closing listener for the popup.

Parameters
p the JPopupMenu
Returns
  • the new window-closing listener

protected void fireMenuCanceled ()

Notifies all listeners that have registered interest for notification on this event type. The event instance is created lazily.

Throws
Error if there is a null listener

protected void fireMenuDeselected ()

Notifies all listeners that have registered interest for notification on this event type. The event instance is created lazily.

Throws
Error if there is a null listener

protected void fireMenuSelected ()

Notifies all listeners that have registered interest for notification on this event type. The event instance is created lazily.

Throws
Error if there is a null listener

protected Point getPopupMenuOrigin ()

Computes the origin for the JMenu's popup menu. This method uses Look and Feel properties named Menu.menuPopupOffsetX, Menu.menuPopupOffsetY, Menu.submenuPopupOffsetX, and Menu.submenuPopupOffsetY to adjust the exact location of popup.

Returns
  • a Point in the coordinate space of the menu which should be used as the origin of the JMenu's popup menu

protected String paramString ()

Returns a string representation of this JMenu. This method is intended to be used only for debugging purposes, and the content and format of the returned string may vary between implementations. The returned string may be empty but may not be null.

Returns
  • a string representation of this JMenu.

protected void processKeyEvent (KeyEvent evt)

Processes key stroke events such as mnemonics and accelerators.

Parameters
evt the key event to be processed