CheckboxMenuItem (Java Platform SE 8 ) (original) (raw)

• java.lang.Object

• • java.awt.MenuComponent
  • • java.awt.MenuItem
      • • java.awt.CheckboxMenuItem

• All Implemented Interfaces:
  ItemSelectable, Serializable, Accessible

public class CheckboxMenuItem
extends MenuItem
implements ItemSelectable, Accessible
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:

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.
Since:
JDK1.0
See Also:
ItemEvent, ItemListener, Serialized Form

• • Nested Class Summary

  Nested Classes

  Modifier and Type	Class	Description
  protected class	CheckboxMenuItem.AccessibleAWTCheckboxMenuItem	Inner class of CheckboxMenuItem used to provide default support for accessibility.

     * ### Nested classes/interfaces inherited from class java.awt.[MenuItem](../../java/awt/MenuItem.html "class in java.awt")  
     `[MenuItem.AccessibleAWTMenuItem](../../java/awt/MenuItem.AccessibleAWTMenuItem.html "class in java.awt")`  
     * ### Nested classes/interfaces inherited from class java.awt.[MenuComponent](../../java/awt/MenuComponent.html "class in java.awt")  
     `[MenuComponent.AccessibleAWTMenuComponent](../../java/awt/MenuComponent.AccessibleAWTMenuComponent.html "class in java.awt")`  

  • Constructor Summary

  Constructors

  Constructor	Description
  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.

  • Method Summary

  All Methods Instance Methods Concrete Methods

  Modifier and Type	Method	Description
  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.
  ItemListener[]	getItemListeners()	Returns an array of all the item listeners registered on this checkbox menuitem.
  <T extends EventListener>T[]	getListeners(Class listenerType)	Returns an array of all the objects currently registered as _Foo_Listeners upon this CheckboxMenuItem.
  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 thisCheckBoxMenuItem.
  protected void	processEvent(AWTEvent e)	Processes events on this check box menu item.
  protected void	processItemEvent(ItemEvent e)	Processes item events occurring on this check box menu item by dispatching them to any registered ItemListener objects.
  void	removeItemListener(ItemListener l)	Removes the specified item listener so that it no longer receives item events from this check box menu item.
  void	setState(boolean b)	Sets this check box menu item to the specified state.

     * ### Methods inherited from class java.awt.[MenuItem](../../java/awt/MenuItem.html "class in java.awt")  
     `[addActionListener](../../java/awt/MenuItem.html#addActionListener-java.awt.event.ActionListener-), [deleteShortcut](../../java/awt/MenuItem.html#deleteShortcut--), [disable](../../java/awt/MenuItem.html#disable--), [disableEvents](../../java/awt/MenuItem.html#disableEvents-long-), [enable](../../java/awt/MenuItem.html#enable--), [enable](../../java/awt/MenuItem.html#enable-boolean-), [enableEvents](../../java/awt/MenuItem.html#enableEvents-long-), [getActionCommand](../../java/awt/MenuItem.html#getActionCommand--), [getActionListeners](../../java/awt/MenuItem.html#getActionListeners--), [getLabel](../../java/awt/MenuItem.html#getLabel--), [getShortcut](../../java/awt/MenuItem.html#getShortcut--), [isEnabled](../../java/awt/MenuItem.html#isEnabled--), [processActionEvent](../../java/awt/MenuItem.html#processActionEvent-java.awt.event.ActionEvent-), [removeActionListener](../../java/awt/MenuItem.html#removeActionListener-java.awt.event.ActionListener-), [setActionCommand](../../java/awt/MenuItem.html#setActionCommand-java.lang.String-), [setEnabled](../../java/awt/MenuItem.html#setEnabled-boolean-), [setLabel](../../java/awt/MenuItem.html#setLabel-java.lang.String-), [setShortcut](../../java/awt/MenuItem.html#setShortcut-java.awt.MenuShortcut-)`  
     * ### Methods inherited from class java.awt.[MenuComponent](../../java/awt/MenuComponent.html "class in java.awt")  
     `[dispatchEvent](../../java/awt/MenuComponent.html#dispatchEvent-java.awt.AWTEvent-), [getFont](../../java/awt/MenuComponent.html#getFont--), [getName](../../java/awt/MenuComponent.html#getName--), [getParent](../../java/awt/MenuComponent.html#getParent--), [getPeer](../../java/awt/MenuComponent.html#getPeer--), [getTreeLock](../../java/awt/MenuComponent.html#getTreeLock--), [postEvent](../../java/awt/MenuComponent.html#postEvent-java.awt.Event-), [removeNotify](../../java/awt/MenuComponent.html#removeNotify--), [setFont](../../java/awt/MenuComponent.html#setFont-java.awt.Font-), [setName](../../java/awt/MenuComponent.html#setName-java.lang.String-), [toString](../../java/awt/MenuComponent.html#toString--)`  
     * ### Methods inherited from class java.lang.[Object](../../java/lang/Object.html "class in java.lang")  
     `[clone](../../java/lang/Object.html#clone--), [equals](../../java/lang/Object.html#equals-java.lang.Object-), [finalize](../../java/lang/Object.html#finalize--), [getClass](../../java/lang/Object.html#getClass--), [hashCode](../../java/lang/Object.html#hashCode--), [notify](../../java/lang/Object.html#notify--), [notifyAll](../../java/lang/Object.html#notifyAll--), [wait](../../java/lang/Object.html#wait--), [wait](../../java/lang/Object.html#wait-long-), [wait](../../java/lang/Object.html#wait-long-int-)`

• • Constructor Detail

     * #### CheckboxMenuItem  
     public CheckboxMenuItem()  
                      throws [HeadlessException](../../java/awt/HeadlessException.html "class in java.awt")  
     Create a check box menu item with an empty label. The item's state is initially set to "off."  
     Throws:  
     `[HeadlessException](../../java/awt/HeadlessException.html "class in java.awt")` \- if GraphicsEnvironment.isHeadless() returns true  
     Since:  
     JDK1.1  
     See Also:  
     [GraphicsEnvironment.isHeadless()](../../java/awt/GraphicsEnvironment.html#isHeadless--)  
     * #### CheckboxMenuItem  
     public CheckboxMenuItem([String](../../java/lang/String.html "class in java.lang") label)  
                      throws [HeadlessException](../../java/awt/HeadlessException.html "class in java.awt")  
     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](../../java/awt/HeadlessException.html "class in java.awt")` \- if GraphicsEnvironment.isHeadless() returns true  
     See Also:  
     [GraphicsEnvironment.isHeadless()](../../java/awt/GraphicsEnvironment.html#isHeadless--)  
     * #### CheckboxMenuItem  
     public CheckboxMenuItem([String](../../java/lang/String.html "class in java.lang") label,  
                             boolean state)  
                      throws [HeadlessException](../../java/awt/HeadlessException.html "class in java.awt")  
     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](../../java/awt/HeadlessException.html "class in java.awt")` \- if GraphicsEnvironment.isHeadless() returns true  
     Since:  
     JDK1.1  
     See Also:  
     [GraphicsEnvironment.isHeadless()](../../java/awt/GraphicsEnvironment.html#isHeadless--)  

  • Method Detail

    * #### addNotify  
    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.  
    Overrides:  
    `[addNotify](../../java/awt/MenuItem.html#addNotify--)` in class `[MenuItem](../../java/awt/MenuItem.html "class in java.awt")`  
    See Also:  
    [Toolkit.createCheckboxMenuItem(java.awt.CheckboxMenuItem)](../../java/awt/Toolkit.html#createCheckboxMenuItem-java.awt.CheckboxMenuItem-), [Component.getToolkit()](../../java/awt/Component.html#getToolkit--)  
    * #### getState  
    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"  
    See Also:  
    [setState(boolean)](../../java/awt/CheckboxMenuItem.html#setState-boolean-)  
    * #### setState  
    public void setState(boolean b)  
    Sets this check box menu item to the specified 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`  
    See Also:  
    [getState()](../../java/awt/CheckboxMenuItem.html#getState--)  
    * #### getSelectedObjects  
    public [Object](../../java/lang/Object.html "class in java.lang")[] getSelectedObjects()  
    Returns the an array (length 1) containing the checkbox menu item label or null if the checkbox is not selected.  
    Specified by:  
    `[getSelectedObjects](../../java/awt/ItemSelectable.html#getSelectedObjects--)` in interface `[ItemSelectable](../../java/awt/ItemSelectable.html "interface in java.awt")`  
    See Also:  
    [ItemSelectable](../../java/awt/ItemSelectable.html "interface in java.awt")  
    * #### addItemListener  
    public void addItemListener([ItemListener](../../java/awt/event/ItemListener.html "interface in java.awt.event") 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](doc-files/AWTThreadIssues.html#ListenersThreads) for details on AWT's threading model.  
    Specified by:  
    `[addItemListener](../../java/awt/ItemSelectable.html#addItemListener-java.awt.event.ItemListener-)` in interface `[ItemSelectable](../../java/awt/ItemSelectable.html "interface in java.awt")`  
    Parameters:  
    `l` \- the item listener  
    Since:  
    JDK1.1  
    See Also:  
    [removeItemListener(java.awt.event.ItemListener)](../../java/awt/CheckboxMenuItem.html#removeItemListener-java.awt.event.ItemListener-), [getItemListeners()](../../java/awt/CheckboxMenuItem.html#getItemListeners--), [setState(boolean)](../../java/awt/CheckboxMenuItem.html#setState-boolean-), [ItemEvent](../../java/awt/event/ItemEvent.html "class in java.awt.event"), [ItemListener](../../java/awt/event/ItemListener.html "interface in java.awt.event")  
    * #### removeItemListener  
    public void removeItemListener([ItemListener](../../java/awt/event/ItemListener.html "interface in java.awt.event") 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](doc-files/AWTThreadIssues.html#ListenersThreads) for details on AWT's threading model.  
    Specified by:  
    `[removeItemListener](../../java/awt/ItemSelectable.html#removeItemListener-java.awt.event.ItemListener-)` in interface `[ItemSelectable](../../java/awt/ItemSelectable.html "interface in java.awt")`  
    Parameters:  
    `l` \- the item listener  
    Since:  
    JDK1.1  
    See Also:  
    [addItemListener(java.awt.event.ItemListener)](../../java/awt/CheckboxMenuItem.html#addItemListener-java.awt.event.ItemListener-), [getItemListeners()](../../java/awt/CheckboxMenuItem.html#getItemListeners--), [ItemEvent](../../java/awt/event/ItemEvent.html "class in java.awt.event"), [ItemListener](../../java/awt/event/ItemListener.html "interface in java.awt.event")  
    * #### getItemListeners  
    public [ItemListener](../../java/awt/event/ItemListener.html "interface in java.awt.event")[] getItemListeners()  
    Returns an array of all the item listeners registered on this checkbox menuitem.  
    Returns:  
    all of this checkbox menuitem's `ItemListener`s or an empty array if no item listeners are currently registered  
    Since:  
    1.4  
    See Also:  
    [addItemListener(java.awt.event.ItemListener)](../../java/awt/CheckboxMenuItem.html#addItemListener-java.awt.event.ItemListener-), [removeItemListener(java.awt.event.ItemListener)](../../java/awt/CheckboxMenuItem.html#removeItemListener-java.awt.event.ItemListener-), [ItemEvent](../../java/awt/event/ItemEvent.html "class in java.awt.event"), [ItemListener](../../java/awt/event/ItemListener.html "interface in java.awt.event")  
    * #### getListeners  
    public <T extends [EventListener](../../java/util/EventListener.html "interface in java.util")> T[] getListeners([Class](../../java/lang/Class.html "class in java.lang")<T> listenerType)  
    Returns an array of all the objects currently registered as `_Foo_Listener`s upon this `CheckboxMenuItem`.`_Foo_Listener`s are registered using the`add_Foo_Listener` method.  
     You can specify the `listenerType` argument with a class literal, such as`_Foo_Listener.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.  
    Overrides:  
    `[getListeners](../../java/awt/MenuItem.html#getListeners-java.lang.Class-)` in class `[MenuItem](../../java/awt/MenuItem.html "class in java.awt")`  
    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`_Foo_Listener`s on this checkbox menuitem, or an empty array if no such listeners have been added  
    Throws:  
    `[ClassCastException](../../java/lang/ClassCastException.html "class in java.lang")` \- if `listenerType` doesn't specify a class or interface that implements`java.util.EventListener`  
    Since:  
    1.3  
    See Also:  
    [getItemListeners()](../../java/awt/CheckboxMenuItem.html#getItemListeners--)  
    * #### processEvent  
    protected void processEvent([AWTEvent](../../java/awt/AWTEvent.html "class in java.awt") 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.  
    Overrides:  
    `[processEvent](../../java/awt/MenuItem.html#processEvent-java.awt.AWTEvent-)` in class `[MenuItem](../../java/awt/MenuItem.html "class in java.awt")`  
    Parameters:  
    `e` \- the event  
    Since:  
    JDK1.1  
    See Also:  
    [ItemEvent](../../java/awt/event/ItemEvent.html "class in java.awt.event"), [processItemEvent(java.awt.event.ItemEvent)](../../java/awt/CheckboxMenuItem.html#processItemEvent-java.awt.event.ItemEvent-)  
    * #### processItemEvent  
    protected void processItemEvent([ItemEvent](../../java/awt/event/ItemEvent.html "class in java.awt.event") 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  
    Since:  
    JDK1.1  
    See Also:  
    [ItemEvent](../../java/awt/event/ItemEvent.html "class in java.awt.event"), [ItemListener](../../java/awt/event/ItemListener.html "interface in java.awt.event"), [addItemListener(java.awt.event.ItemListener)](../../java/awt/CheckboxMenuItem.html#addItemListener-java.awt.event.ItemListener-), [MenuItem.enableEvents(long)](../../java/awt/MenuItem.html#enableEvents-long-)  
    * #### paramString  
    public [String](../../java/lang/String.html "class in java.lang") 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`.  
    Overrides:  
    `[paramString](../../java/awt/MenuItem.html#paramString--)` in class `[MenuItem](../../java/awt/MenuItem.html "class in java.awt")`  
    Returns:  
    the parameter string of this check box menu item  
    * #### getAccessibleContext  
    public [AccessibleContext](../../javax/accessibility/AccessibleContext.html "class in javax.accessibility") 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.  
    Specified by:  
    `[getAccessibleContext](../../javax/accessibility/Accessible.html#getAccessibleContext--)` in interface `[Accessible](../../javax/accessibility/Accessible.html "interface in javax.accessibility")`  
    Overrides:  
    `[getAccessibleContext](../../java/awt/MenuItem.html#getAccessibleContext--)` in class `[MenuItem](../../java/awt/MenuItem.html "class in java.awt")`  
    Returns:  
    an AccessibleAWTCheckboxMenuItem that serves as the AccessibleContext of this CheckboxMenuItem  
    Since:  
    1.3

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