Class CheckboxMenuItem

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.

Constructors

CheckboxMenuItem

public CheckboxMenuItem()
                 throws HeadlessException

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

Since:

JDK1.1

See Also:

GraphicsEnvironment.isHeadless()

CheckboxMenuItem

public CheckboxMenuItem(String label)
                 throws HeadlessException

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

See Also:

GraphicsEnvironment.isHeadless()

CheckboxMenuItem

public CheckboxMenuItem(String label,
                        boolean state)
                 throws HeadlessException

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

Since:

JDK1.1

See Also:

GraphicsEnvironment.isHeadless()

Methods

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 in class MenuItem

See Also:

Toolkit.createCheckboxMenuItem(java.awt.CheckboxMenuItem), Component.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)

setState

public void setState(boolean b)

Parameters:

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

See Also:

getState()

getSelectedObjects

public Object[] getSelectedObjects()

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

Specified by:

getSelectedObjects in interface ItemSelectable

See Also:

ItemSelectable

addItemListener

public void addItemListener(ItemListener l)

Specified by:

addItemListener in interface ItemSelectable

Parameters:

l - the item listener

Since:

JDK1.1

See Also:

removeItemListener(java.awt.event.ItemListener), getItemListeners(), setState(boolean), ItemEvent, ItemListener

removeItemListener

public void removeItemListener(ItemListener l)

Specified by:

removeItemListener in interface ItemSelectable

Parameters:

l - the item listener

Since:

JDK1.1

See Also:

addItemListener(java.awt.event.ItemListener), getItemListeners(), ItemEvent, ItemListener

getItemListeners

public 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

Since:

1.4

See Also:

addItemListener(java.awt.event.ItemListener), removeItemListener(java.awt.event.ItemListener), ItemEvent, ItemListener

getListeners

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

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

Overrides:

getListeners in class MenuItem

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

Since:

1.3

See Also:

getItemListeners()

processEvent

protected void processEvent(AWTEvent e)

Overrides:

processEvent in class MenuItem

Parameters:

e - the event

Since:

JDK1.1

See Also:

ItemEvent, processItemEvent(java.awt.event.ItemEvent)

processItemEvent

protected void processItemEvent(ItemEvent e)

Parameters:

e - the item event

Since:

JDK1.1

See Also:

ItemEvent, ItemListener, addItemListener(java.awt.event.ItemListener), MenuItem.enableEvents(long)

paramString

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.

Overrides:

paramString in class MenuItem

Returns:

the parameter string of this check box menu item

getAccessibleContext

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.

Specified by:

getAccessibleContext in interface Accessible

Overrides:

getAccessibleContext in class MenuItem

Returns:

an AccessibleAWTCheckboxMenuItem that serves as the AccessibleContext of this CheckboxMenuItem

Since:

1.3