Class MenuItem
- All Implemented Interfaces:
Serializable,Accessible
- Direct Known Subclasses:
CheckboxMenuItem,Menu
MenuItem, or one of its subclasses.
The default MenuItem object embodies
a simple labeled menu item.
This picture of a menu bar shows five menu items:
The first two items are simple menu items, labeled
"Basic" and "Simple".
Following these two items is a separator, which is itself
a menu item, created with the label "-".
Next is an instance of CheckboxMenuItem
labeled "Check". The final menu item is a
submenu labeled "More Examples",
and this submenu is an instance of Menu.
When a menu item is selected, AWT sends an action event to
the menu item. Since the event is an
instance of ActionEvent, the processEvent
method examines the event and passes it along to
processActionEvent. The latter method redirects the
event to any ActionListener objects that have
registered an interest in action events generated by this
menu item.
Note that the subclass Menu overrides this behavior and
does not send any event to the frame until one of its subitems is
selected.
- See Also:
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Nested Class Summary
Nested ClassesModifier and TypeClassDescriptionprotected classInner class of MenuItem used to provide default support for accessibility.Nested classes/interfaces declared in class java.awt.MenuComponent
MenuComponent.AccessibleAWTMenuComponent -
Constructor Summary
ConstructorsConstructorDescriptionMenuItem()Constructs a new MenuItem with an empty label and no keyboard shortcut.Constructs a new MenuItem with the specified label and no keyboard shortcut.MenuItem(String label, MenuShortcut s) Create a menu item with an associated keyboard shortcut. -
Method Summary
Modifier and TypeMethodDescriptionvoidAdds the specified action listener to receive action events from this menu item.voidCreates the menu item's peer.voidDelete anyMenuShortcutobject associated with this menu item.voiddisable()Deprecated.protected final voiddisableEvents(long eventsToDisable) Disables event delivery to this menu item for events defined by the specified event mask parameter.voidenable()Deprecated.As of JDK version 1.1, replaced bysetEnabled(boolean).voidenable(boolean b) Deprecated.As of JDK version 1.1, replaced bysetEnabled(boolean).protected final voidenableEvents(long eventsToEnable) Enables event delivery to this menu item for events to be defined by the specified event mask parameterGets the AccessibleContext associated with this MenuItem.Gets the command name of the action event that is fired by this menu item.Returns an array of all the action listeners registered on this menu item.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 asFooListeners upon thisMenuItem.Get theMenuShortcutobject associated with this menu item,booleanChecks whether this menu item is enabled.Returns a string representing the state of thisMenuItem.protected voidProcesses action events occurring on this menu item, by dispatching them to any registeredActionListenerobjects.protected voidProcesses events on this menu item.voidRemoves the specified action listener so it no longer receives action events from this menu item.voidsetActionCommand(String command) Sets the command name of the action event that is fired by this menu item.voidsetEnabled(boolean b) Sets whether or not this menu item can be chosen.voidSets the label for this menu item to the specified label.voidSet theMenuShortcutobject associated with this menu item.Methods declared in class java.awt.MenuComponent
dispatchEvent, getFont, getName, getParent, getTreeLock, postEvent, removeNotify, setFont, setName, toString
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Constructor Details
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MenuItem
Constructs a new MenuItem with an empty label and no keyboard shortcut.- Throws:
HeadlessException- if GraphicsEnvironment.isHeadless() returns true.- Since:
- 1.1
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MenuItem
Constructs a new MenuItem with the specified label and no keyboard shortcut. Note that use of "-" in a label is reserved to indicate a separator between menu items. By default, all menu items except for separators are enabled.- Parameters:
label- the label for this menu item.- Throws:
HeadlessException- if GraphicsEnvironment.isHeadless() returns true.- Since:
- 1.0
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MenuItem
Create a menu item with an associated keyboard shortcut. Note that use of "-" in a label is reserved to indicate a separator between menu items. By default, all menu items except for separators are enabled.- Parameters:
label- the label for this menu item.s- the instance ofMenuShortcutassociated with this menu item.- Throws:
HeadlessException- if GraphicsEnvironment.isHeadless() returns true.- Since:
- 1.1
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Method Details
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addNotify
public void addNotify()Creates the menu item's peer. The peer allows us to modify the appearance of the menu item without changing its functionality. -
getLabel
Gets the label for this menu item.- Returns:
- the label of this menu item, or
nullif this menu item has no label. - Since:
- 1.0
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setLabel
Sets the label for this menu item to the specified label.- Parameters:
label- the new label, ornullfor no label.- Since:
- 1.0
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isEnabled
public boolean isEnabled()Checks whether this menu item is enabled.- Returns:
trueif the item is enabled; otherwisefalse- Since:
- 1.0
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setEnabled
public void setEnabled(boolean b) Sets whether or not this menu item can be chosen.- Parameters:
b- iftrue, enables this menu item; iffalse, disables it.- Since:
- 1.1
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enable
Deprecated.As of JDK version 1.1, replaced bysetEnabled(boolean). -
enable
Deprecated.As of JDK version 1.1, replaced bysetEnabled(boolean).Sets whether or not this menu item can be chosen.- Parameters:
b- iftrue, enables this menu item; otherwise disables
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disable
Deprecated.As of JDK version 1.1, replaced bysetEnabled(boolean). -
getShortcut
Get theMenuShortcutobject associated with this menu item,- Returns:
- the menu shortcut associated with this menu item,
or
nullif none has been specified. - Since:
- 1.1
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setShortcut
Set theMenuShortcutobject associated with this menu item. If a menu shortcut is already associated with this menu item, it is replaced.- Parameters:
s- the menu shortcut to associate with this menu item.- Since:
- 1.1
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deleteShortcut
public void deleteShortcut()Delete anyMenuShortcutobject associated with this menu item.- Since:
- 1.1
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enableEvents
protected final void enableEvents(long eventsToEnable) Enables event delivery to this menu item for events to be defined by the specified event mask parameterSince 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
MenuItemwhich desire to have the specified event types delivered toprocessEventregardless of whether a listener is registered.- Parameters:
eventsToEnable- the event mask defining the event types- Since:
- 1.1
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disableEvents
protected final void disableEvents(long eventsToDisable) Disables event delivery to this menu item for events defined by the specified event mask parameter.- Parameters:
eventsToDisable- the event mask defining the event types- Since:
- 1.1
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setActionCommand
Sets the command name of the action event that is fired by this menu item.By default, the action command is set to the label of the menu item.
- Parameters:
command- the action command to be set for this menu item.- Since:
- 1.1
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getActionCommand
Gets the command name of the action event that is fired by this menu item.- Returns:
- the action command name
- Since:
- 1.1
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addActionListener
Adds the specified action listener to receive action events from this 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 action listener.- Since:
- 1.1
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removeActionListener
Removes the specified action listener so it no longer receives action events from this 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 action listener.- Since:
- 1.1
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getActionListeners
Returns an array of all the action listeners registered on this menu item.- Returns:
- all of this menu item's
ActionListeners or an empty array if no action listeners are currently registered - Since:
- 1.4
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getListeners
Returns an array of all the objects currently registered asFooListeners upon thisMenuItem.FooListeners are registered using theaddFooListenermethod.You can specify the
listenerTypeargument with a class literal, such asFooListener.class. For example, you can query aMenuItem mfor its action listeners with the following code:ActionListener[] als = (ActionListener[])(m.getListeners(ActionListener.class));
If no such listeners exist, this method returns an empty array.- Type Parameters:
T- the type of the listeners- Parameters:
listenerType- the type of listeners requested; this parameter should specify an interface that descends fromjava.util.EventListener- Returns:
- an array of all objects registered as
FooListeners on this menu item, or an empty array if no such listeners have been added - Throws:
ClassCastException- iflistenerTypedoesn't specify a class or interface that implementsjava.util.EventListener- Since:
- 1.3
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processEvent
Processes events on this menu item. If the event is an instance ofActionEvent, it invokesprocessActionEvent, another method defined byMenuItem.Currently, menu items only support action events.
Note that if the event parameter is
nullthe behavior is unspecified and may result in an exception.- Overrides:
processEventin classMenuComponent- Parameters:
e- the event- Since:
- 1.1
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processActionEvent
Processes action events occurring on this menu item, by dispatching them to any registeredActionListenerobjects. This method is not called unless action events are enabled for this component. Action events are enabled when one of the following occurs:- An
ActionListenerobject is registered viaaddActionListener. - Action events are enabled via
enableEvents.
Note that if the event parameter is
nullthe behavior is unspecified and may result in an exception.- Parameters:
e- the action event- Since:
- 1.1
- See Also:
- An
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paramString
Returns a string representing the state of thisMenuItem. 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 benull.- Overrides:
paramStringin classMenuComponent- Returns:
- the parameter string of this menu item
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getAccessibleContext
Gets the AccessibleContext associated with this MenuItem. For menu items, the AccessibleContext takes the form of an AccessibleAWTMenuItem. A new AccessibleAWTMenuItem instance is created if necessary.- Specified by:
getAccessibleContextin interfaceAccessible- Overrides:
getAccessibleContextin classMenuComponent- Returns:
- an AccessibleAWTMenuItem that serves as the AccessibleContext of this MenuItem
- Since:
- 1.3
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setEnabled(boolean).