public class MenuItem extends MenuComponent implements Accessible
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.
Modifier and Type | Class and Description |
---|---|
protected class |
MenuItem.AccessibleAWTMenuItem
Inner class of MenuItem used to provide default support for
accessibility.
|
MenuComponent.AccessibleAWTMenuComponent
Constructor and Description |
---|
MenuItem()
Constructs a new MenuItem with an empty label and no keyboard
shortcut.
|
MenuItem(String label)
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.
|
Modifier and Type | Method and Description |
---|---|
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. |
void |
disable()
Deprecated.
As of JDK version 1.1,
replaced by
setEnabled(boolean) . |
protected void |
disableEvents(long eventsToDisable)
Disables event delivery to this menu item for events
defined by the specified event mask parameter.
|
void |
enable()
Deprecated.
As of JDK version 1.1,
replaced by
setEnabled(boolean) . |
void |
enable(boolean b)
Deprecated.
As of JDK version 1.1,
replaced by
setEnabled(boolean) . |
protected void |
enableEvents(long eventsToEnable)
Enables event delivery to this menu item for events
to be defined by the specified event mask parameter
|
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.
|
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> |
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 . |
protected void |
processActionEvent(ActionEvent e)
Processes action events occurring on this menu item,
by dispatching them to any registered
ActionListener objects. |
protected void |
processEvent(AWTEvent e)
Processes events on this menu item.
|
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.
|
void |
setEnabled(boolean b)
Sets whether or not this menu item can be chosen.
|
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. |
dispatchEvent, getFont, getName, getParent, getPeer, getTreeLock, postEvent, removeNotify, setFont, setName, toString
public MenuItem() throws HeadlessException
HeadlessException
- if GraphicsEnvironment.isHeadless()
returns true.GraphicsEnvironment.isHeadless()
public MenuItem(String label) throws HeadlessException
label
- the label for this menu item.HeadlessException
- if GraphicsEnvironment.isHeadless()
returns true.GraphicsEnvironment.isHeadless()
public MenuItem(String label, MenuShortcut s) throws HeadlessException
label
- the label for this menu item.s
- the instance of MenuShortcut
associated with this menu item.HeadlessException
- if GraphicsEnvironment.isHeadless()
returns true.GraphicsEnvironment.isHeadless()
public void addNotify()
public String getLabel()
null
if this menu item has no label.setLabel(java.lang.String)
public void setLabel(String label)
label
- the new label, or null
for no label.getLabel()
public boolean isEnabled()
setEnabled(boolean)
public void setEnabled(boolean b)
b
- if true
, enables this menu item;
if false
, disables it.isEnabled()
@Deprecated public void enable()
setEnabled(boolean)
.@Deprecated public void enable(boolean b)
setEnabled(boolean)
.@Deprecated public void disable()
setEnabled(boolean)
.public MenuShortcut getShortcut()
MenuShortcut
object associated with this
menu item,null
if none has been specified.setShortcut(java.awt.MenuShortcut)
public void setShortcut(MenuShortcut s)
MenuShortcut
object associated with this
menu item. If a menu shortcut is already associated with
this menu item, it is replaced.s
- the menu shortcut to associate
with this menu item.getShortcut()
public void deleteShortcut()
MenuShortcut
object associated
with this menu item.protected final void enableEvents(long eventsToEnable)
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.
eventsToEnable
- the event mask defining the event typesprocessEvent(java.awt.AWTEvent)
,
disableEvents(long)
,
Component.enableEvents(long)
protected final void disableEvents(long eventsToDisable)
eventsToDisable
- the event mask defining the event typesprocessEvent(java.awt.AWTEvent)
,
enableEvents(long)
,
Component.disableEvents(long)
public void setActionCommand(String command)
By default, the action command is set to the label of the menu item.
command
- the action command to be set
for this menu item.getActionCommand()
public String getActionCommand()
setActionCommand(java.lang.String)
public void addActionListener(ActionListener l)
Refer to AWT Threading Issues for details on AWT's threading model.
l
- the action listener.removeActionListener(java.awt.event.ActionListener)
,
getActionListeners()
,
ActionEvent
,
ActionListener
public void removeActionListener(ActionListener l)
Refer to AWT Threading Issues for details on AWT's threading model.
l
- the action listener.addActionListener(java.awt.event.ActionListener)
,
getActionListeners()
,
ActionEvent
,
ActionListener
public ActionListener[] getActionListeners()
ActionListener
s
or an empty array if no action
listeners are currently registeredaddActionListener(java.awt.event.ActionListener)
,
removeActionListener(java.awt.event.ActionListener)
,
ActionEvent
,
ActionListener
public <T extends EventListener> T[] getListeners(Class<T> listenerType)
FooListener
s
upon this MenuItem
.
FooListener
s 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
MenuItem
m
for 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.
listenerType
- the type of listeners requested; this parameter
should specify an interface that descends from
java.util.EventListener
FooListener
s on this menu item,
or an empty array if no such
listeners have been addedClassCastException
- if listenerType
doesn't specify a class or interface that implements
java.util.EventListener
getActionListeners()
protected void processEvent(AWTEvent e)
ActionEvent
, it invokes
processActionEvent
, another method
defined by MenuItem
.
Currently, menu items only support action events.
Note that if the event parameter is null
the behavior is unspecified and may result in an
exception.
processEvent
in class MenuComponent
e
- the eventprocessActionEvent(java.awt.event.ActionEvent)
protected void processActionEvent(ActionEvent e)
ActionListener
objects.
This method is not called unless action events are
enabled for this component. Action events are enabled
when one of the following occurs:
ActionListener
object is registered
via addActionListener
.
enableEvents
.
Note that if the event parameter is null
the behavior is unspecified and may result in an
exception.
e
- the action eventActionEvent
,
ActionListener
,
enableEvents(long)
public String paramString()
MenuItem
.
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
.paramString
in class MenuComponent
public AccessibleContext getAccessibleContext()
getAccessibleContext
in interface Accessible
getAccessibleContext
in class MenuComponent
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For further API reference and developer documentation, see Java SE Documentation. That documentation contains more detailed, developer-targeted descriptions, with conceptual overviews, definitions of terms, workarounds, and working code examples.
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