public class

CheckboxMenuItem

extends MenuItem
implements ItemSelectable Accessible

java.lang.Object
↳	java.awt.MenuComponent
	↳	java.awt.MenuItem
		↳	java.awt.CheckboxMenuItem

Class Overview

This class represents a check box that can be included in a menu. Selecting the check box in the menu changes its state from "on" to "off" or from "off" to "on."

The following picture depicts a menu which contains an instance of CheckBoxMenuItem:

Menu labeled Examples, containing items Basic, Simple, Check, and More Examples. The Check item is a CheckBoxMenuItem instance, in the off state.

The item labeled Check shows a check box menu item in its "off" state.

When a check box menu item is selected, AWT sends an item event to the item. Since the event is an instance of ItemEvent, the processEvent method examines the event and passes it along to processItemEvent. The latter method redirects the event to any ItemListener objects that have registered an interest in item events generated by this menu item.

Summary

Nested Classes
class	CheckboxMenuItem.AccessibleAWTCheckboxMenuItem	Inner class of CheckboxMenuItem used to provide default support for accessibility.

Public Constructors
	CheckboxMenuItem() Create a check box menu item with an empty label.
	CheckboxMenuItem(String label) Create a check box menu item with the specified label.
	CheckboxMenuItem(String label, boolean state) Create a check box menu item with the specified label and state.

Public Methods
synchronized void	addItemListener(ItemListener l) Adds the specified item listener to receive item events from this check box menu item.
void	addNotify() Creates the peer of the checkbox item.
AccessibleContext	getAccessibleContext() Gets the AccessibleContext associated with this CheckboxMenuItem.
synchronized ItemListener[]	getItemListeners() Returns an array of all the item listeners registered on this checkbox menuitem.
<T extends EventListener> T[]	getListeners(Class<T> listenerType) Returns an array of all the objects currently registered as `FooListener`s upon this `CheckboxMenuItem`.
synchronized Object[]	getSelectedObjects() Returns the an array (length 1) containing the checkbox menu item label or null if the checkbox is not selected.
boolean	getState() Determines whether the state of this check box menu item is "on" or "off."
String	paramString() Returns a string representing the state of this `CheckBoxMenuItem`.
synchronized void	removeItemListener(ItemListener l) Removes the specified item listener so that it no longer receives item events from this check box menu item.
synchronized void	setState(boolean b) Sets this check box menu item to the specifed state.

Protected Methods
void	processEvent(AWTEvent e) Processes events on this check box menu item.
void	processItemEvent(ItemEvent e) Processes item events occurring on this check box menu item by dispatching them to any registered `ItemListener` objects.

[Expand]

Inherited Methods

From class java.awt.MenuItem

synchronized void	addActionListener(ActionListener l) Adds the specified action listener to receive action events from this menu item.
void	addNotify() Creates the menu item's peer.
void	deleteShortcut() Delete any `MenuShortcut` object associated with this menu item.
synchronized void	disable() This method is deprecated. As of JDK version 1.1, replaced by `setEnabled(boolean)`.
final void	disableEvents(long eventsToDisable) Disables event delivery to this menu item for events defined by the specified event mask parameter.
synchronized void	enable() This method is deprecated. As of JDK version 1.1, replaced by `setEnabled(boolean)`.
void	enable(boolean b) This method is deprecated. As of JDK version 1.1, replaced by `setEnabled(boolean)`.
final void	enableEvents(long eventsToEnable) Enables event delivery to this menu item for events to be defined by the specified event mask parameter Since event types are automatically enabled when a listener for that type is added to the menu item, this method only needs to be invoked by subclasses of `MenuItem` which desire to have the specified event types delivered to `processEvent` regardless of whether a listener is registered.
AccessibleContext	getAccessibleContext() Gets the AccessibleContext associated with this MenuItem.
String	getActionCommand() Gets the command name of the action event that is fired by this menu item.
synchronized ActionListener[]	getActionListeners() Returns an array of all the action listeners registered on this menu item.
String	getLabel() Gets the label for this menu item.
<T extends EventListener> T[]	getListeners(Class<T> listenerType) Returns an array of all the objects currently registered as `FooListener`s upon this `MenuItem`.
MenuShortcut	getShortcut() Get the `MenuShortcut` object associated with this menu item,
boolean	isEnabled() Checks whether this menu item is enabled.
String	paramString() Returns a string representing the state of this `MenuItem`.
void	processActionEvent(ActionEvent e) Processes action events occurring on this menu item, by dispatching them to any registered `ActionListener` objects.
void	processEvent(AWTEvent e) Processes events on this menu item.
synchronized void	removeActionListener(ActionListener l) Removes the specified action listener so it no longer receives action events from this menu item.
void	setActionCommand(String command) Sets the command name of the action event that is fired by this menu item.
synchronized void	setEnabled(boolean b) Sets whether or not this menu item can be chosen.
synchronized void	setLabel(String label) Sets the label for this menu item to the specified label.
void	setShortcut(MenuShortcut s) Set the `MenuShortcut` object associated with this menu item.

From class java.awt.MenuComponent

final void	dispatchEvent(AWTEvent e) Delivers an event to this component or one of its sub components.
AccessibleContext	getAccessibleContext() Gets the `AccessibleContext` associated with this `MenuComponent`.
Font	getFont() Gets the font used for this menu component.
String	getName() Gets the name of the menu component.
MenuContainer	getParent() Returns the parent container for this menu component.
MenuComponentPeer	getPeer() This method is deprecated. As of JDK version 1.1, programs should not directly manipulate peers.
final Object	getTreeLock() Gets this component's locking object (the object that owns the thread sychronization monitor) for AWT component-tree and layout operations.
String	paramString() Returns a string representing the state of this `MenuComponent`.
boolean	postEvent(Event evt) This method is deprecated. As of JDK version 1.1, replaced by `dispatchEvent`.
void	processEvent(AWTEvent e) Processes events occurring on this menu component.
void	removeNotify() Removes the menu component's peer.
void	setFont(Font f) Sets the font to be used for this menu component to the specified font.
void	setName(String name) Sets the name of the component to the specified string.
String	toString() Returns a representation of this menu component as a string.

From class java.lang.Object

Object	clone() Creates and returns a copy of this object.
boolean	equals(Object obj) Indicates whether some other object is "equal to" this one.
void	finalize() Called by the garbage collector on an object when garbage collection determines that there are no more references to the object.
final Class<?>	getClass() Returns the runtime class of this `Object`.
int	hashCode() Returns a hash code value for the object.
final void	notify() Wakes up a single thread that is waiting on this object's monitor.
final void	notifyAll() Wakes up all threads that are waiting on this object's monitor.
String	toString() Returns a string representation of the object.
final void	wait() Causes the current thread to wait until another thread invokes the `notify()` method or the `notifyAll()` method for this object.
final void	wait(long timeout, int nanos) Causes the current thread to wait until another thread invokes the `notify()` method or the `notifyAll()` method for this object, or some other thread interrupts the current thread, or a certain amount of real time has elapsed.
final void	wait(long timeout) Causes the current thread to wait until either another thread invokes the `notify()` method or the `notifyAll()` method for this object, or a specified amount of time has elapsed.

From interface java.awt.ItemSelectable

From interface javax.accessibility.Accessible

Public Constructors

public CheckboxMenuItem ()

Create a check box menu item with an empty label. The item's state is initially set to "off."

Throws

HeadlessException	if GraphicsEnvironment.isHeadless() returns true

public CheckboxMenuItem (String label)

Create a check box menu item with the specified label. The item's state is initially set to "off."

Parameters

label	a string label for the check box menu item, or `null` for an unlabeled menu item.

Throws

HeadlessException	if GraphicsEnvironment.isHeadless() returns true

public CheckboxMenuItem (String label, boolean state)

Create a check box menu item with the specified label and state.

Parameters

label	a string label for the check box menu item, or `null` for an unlabeled menu item.
state	the initial state of the menu item, where `true` indicates "on" and `false` indicates "off."

Throws

HeadlessException	if GraphicsEnvironment.isHeadless() returns true

Public Methods

public synchronized void addItemListener (ItemListener l)

Adds the specified item listener to receive item events from this check box menu item. Item events are sent in response to user actions, but not in response to calls to setState(). If l is null, no exception is thrown and no action is performed.

Refer to AWT Threading Issues for details on AWT's threading model.

Parameters

l	the item listener

public void addNotify ()

Creates the peer of the checkbox item. This peer allows us to change the look of the checkbox item without changing its functionality. Most applications do not call this method directly.

public AccessibleContext getAccessibleContext ()

Gets the AccessibleContext associated with this CheckboxMenuItem. For checkbox menu items, the AccessibleContext takes the form of an AccessibleAWTCheckboxMenuItem. A new AccessibleAWTCheckboxMenuItem is created if necessary.

Returns

an AccessibleAWTCheckboxMenuItem that serves as the AccessibleContext of this CheckboxMenuItem

public synchronized ItemListener[] getItemListeners ()

Returns an array of all the item listeners registered on this checkbox menuitem.

Returns

all of this checkbox menuitem's ItemListeners or an empty array if no item listeners are currently registered

public T[] getListeners (Class<T> listenerType)

Returns an array of all the objects currently registered as FooListeners upon this CheckboxMenuItem. FooListeners are registered using the addFooListener method.

You can specify the listenerType argument with a class literal, such as FooListener.class. For example, you can query a CheckboxMenuItem c for its item listeners with the following code:

ItemListener[] ils = (ItemListener[])(c.getListeners(ItemListener.class));

If no such listeners exist, this method returns an empty array.

Parameters

listenerType	the type of listeners requested; this parameter should specify an interface that descends from `java.util.EventListener`

Returns

an array of all objects registered as FooListeners on this checkbox menuitem, or an empty array if no such listeners have been added

Throws

ClassCastException	if `listenerType` doesn't specify a class or interface that implements `java.util.EventListener`

public synchronized Object[] getSelectedObjects ()

Returns the an array (length 1) containing the checkbox menu item label or null if the checkbox is not selected.

public boolean getState ()

Determines whether the state of this check box menu item is "on" or "off."

Returns

the state of this check box menu item, where true indicates "on" and false indicates "off"

public String paramString ()

Returns a string representing the state of this CheckBoxMenuItem. 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

the parameter string of this check box menu item

public synchronized void removeItemListener (ItemListener l)

Removes the specified item listener so that it no longer receives item events from this check box menu item. If l is null, no exception is thrown and no action is performed.

Refer to AWT Threading Issues for details on AWT's threading model.

Parameters

l	the item listener

public synchronized void setState (boolean b)

Sets this check box menu item to the specifed state. The boolean value true indicates "on" while false indicates "off."

Note that this method should be primarily used to initialize the state of the check box menu item. Programmatically setting the state of the check box menu item will not trigger an ItemEvent. The only way to trigger an ItemEvent is by user interaction.

Parameters

b	`true` if the check box menu item is on, otherwise `false`

Protected Methods

protected void processEvent (AWTEvent e)

Processes events on this check box menu item. If the event is an instance of ItemEvent, this method invokes the processItemEvent method. If the event is not an item event, it invokes processEvent on the superclass.

Check box menu items currently support only item events.

Note that if the event parameter is null the behavior is unspecified and may result in an exception.

Parameters

e	the event

protected void processItemEvent (ItemEvent e)

Processes item events occurring on this check box menu item by dispatching them to any registered ItemListener objects.

This method is not called unless item events are enabled for this menu item. Item events are enabled when one of the following occurs:

An ItemListener object is registered via addItemListener.
Item events are enabled via enableEvents.

Note that if the event parameter is null the behavior is unspecified and may result in an exception.

Parameters

e	the item event

Interfaces

Classes

Enums

Exceptions

Errors

CheckboxMenuItem

Class Overview

See Also

Summary

Public Constructors

public CheckboxMenuItem ()

Throws

See Also

public CheckboxMenuItem (String label)

Parameters

Throws

See Also

public CheckboxMenuItem (String label, boolean state)

Parameters

Throws

See Also

Public Methods

public synchronized void addItemListener (ItemListener l)

Parameters

See Also

public void addNotify ()

See Also

public AccessibleContext getAccessibleContext ()

Returns

public synchronized ItemListener[] getItemListeners ()

Returns

See Also

public T[] getListeners (Class<T> listenerType)

Parameters

Returns

Throws

See Also

public synchronized Object[] getSelectedObjects ()

See Also

public boolean getState ()

Returns

See Also

public String paramString ()

Returns

public synchronized void removeItemListener (ItemListener l)

Parameters

See Also

public synchronized void setState (boolean b)

Parameters

See Also

Protected Methods

protected void processEvent (AWTEvent e)

Parameters

See Also

protected void processItemEvent (ItemEvent e)

Parameters

See Also