Class MenuItem

java.lang.Object
java.awt.MenuComponent
java.awt.MenuItem
All Implemented Interfaces:
Serializable, Accessible
Direct Known Subclasses:
CheckboxMenuItem, Menu
public class MenuItem extends MenuComponent implements Accessible
All items in a menu must belong to the class 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 following text describes this graphic.
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:

  • Nested Class Summary

    Nested Classes
    Modifier and Type
    Class
    Description
    protected class 
    MenuItem.AccessibleAWTMenuItem
    Inner class of MenuItem used to provide default support for accessibility.

    Nested classes/interfaces inherited from class MenuComponent

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

  • Constructor Summary

    Constructors
    Constructor
    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.

  • Method Summary

    Modifier and Type
    Method
    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 final 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 final 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>
    T[]
    getListeners(Class<T> listenerType)
    Returns an array of all the objects currently registered as FooListeners 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.

    Methods inherited from class MenuComponent

    dispatchEvent, getFont, getName, getParent, getTreeLock, postEvent, removeNotify, setFont, setName, toString
    Modifier and Type
    Method
    Description
    final void
    dispatchEvent(AWTEvent e)
    Delivers an event to this component or one of its sub components.
    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.
    protected final Object
    getTreeLock()
    Gets this component's locking object (the object that owns the thread synchronization monitor) for AWT component-tree and layout operations.
    boolean
    postEvent(Event evt)
    Deprecated.
    As of JDK version 1.1, replaced by dispatchEvent.
    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.

    Methods inherited from class Object

    clone, equals, finalize, getClass, hashCode, notify, notifyAll, wait, wait, wait
    Modifier and Type
    Method
    Description
    protected Object
    clone()
    Creates and returns a copy of this object.
    boolean
    equals(Object obj)
    Indicates whether some other object is "equal to" this one.
    protected void
    finalize()
    Deprecated, for removal: This API element is subject to removal in a future version.
    Finalization is deprecated and subject to removal in a future release.
    final Class<?>
    getClass()
    Returns the runtime class of this Object.
    int
    hashCode()
    Returns a hash code value for this 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.
    final void
    wait()
    Causes the current thread to wait until it is awakened, typically by being notified or interrupted.
    final void
    wait(long timeoutMillis)
    Causes the current thread to wait until it is awakened, typically by being notified or interrupted, or until a certain amount of real time has elapsed.
    final void
    wait(long timeoutMillis, int nanos)
    Causes the current thread to wait until it is awakened, typically by being notified or interrupted, or until a certain amount of real time has elapsed.

  • Constructor Details

    • MenuItem

      public MenuItem() throws HeadlessException
      Constructs a new MenuItem with an empty label and no keyboard shortcut.
      Throws:
      HeadlessException - if GraphicsEnvironment.isHeadless() returns true.
      Since:
      1.1
      See Also:

    • MenuItem

      public MenuItem(String label) throws HeadlessException
      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
      See Also:

    • MenuItem

      public MenuItem(String label, MenuShortcut s) throws HeadlessException
      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 of MenuShortcut associated with this menu item.
      Throws:
      HeadlessException - if GraphicsEnvironment.isHeadless() returns true.
      Since:
      1.1
      See Also:

  • Method Details

    • 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

      public String getLabel()
      Gets the label for this menu item.
      Returns:
      the label of this menu item, or null if this menu item has no label.
      Since:
      1.0
      See Also:

    • setLabel

      public void setLabel(String label)
      Sets the label for this menu item to the specified label.
      Parameters:
      label - the new label, or null for no label.
      Since:
      1.0
      See Also:

    • isEnabled

      public boolean isEnabled()
      Checks whether this menu item is enabled.
      Returns:
      true if the item is enabled; otherwise false
      Since:
      1.0
      See Also:

    • setEnabled

      public void setEnabled(boolean b)
      Sets whether or not this menu item can be chosen.
      Parameters:
      b - if true, enables this menu item; if false, disables it.
      Since:
      1.1
      See Also:

    • enable

      @Deprecated public void enable()
      Deprecated.
      As of JDK version 1.1, replaced by setEnabled(boolean).

    • enable

      @Deprecated public void enable(boolean b)
      Deprecated.
      As of JDK version 1.1, replaced by setEnabled(boolean).
      Sets whether or not this menu item can be chosen.
      Parameters:
      b - if true, enables this menu item; otherwise disables

    • disable

      @Deprecated public void disable()
      Deprecated.
      As of JDK version 1.1, replaced by setEnabled(boolean).

    • getShortcut

      public MenuShortcut getShortcut()
      Get the MenuShortcut object associated with this menu item,
      Returns:
      the menu shortcut associated with this menu item, or null if none has been specified.
      Since:
      1.1
      See Also:

    • setShortcut

      public void setShortcut(MenuShortcut s)
      Set the MenuShortcut object 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
      See Also:

    • deleteShortcut

      public void deleteShortcut()
      Delete any MenuShortcut object associated with this menu item.
      Since:
      1.1

    • enableEvents

      protected 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.

      Parameters:
      eventsToEnable - the event mask defining the event types
      Since:
      1.1
      See Also:

    • 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
      See Also:

    • setActionCommand

      public void setActionCommand(String command)
      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
      See Also:

    • getActionCommand

      public String getActionCommand()
      Gets the command name of the action event that is fired by this menu item.
      Returns:
      the action command name
      Since:
      1.1
      See Also:

    • addActionListener

      public void addActionListener(ActionListener l)
      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
      See Also:

    • removeActionListener

      public void removeActionListener(ActionListener l)
      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
      See Also:

    • getActionListeners

      public ActionListener[] 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
      See Also:

    • getListeners

      public <T extends EventListener> T[] getListeners(Class<T> listenerType)
      Returns an array of all the objects currently registered as FooListeners upon this MenuItem. 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 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.
      Type Parameters:
      T - the type of the listeners
      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 menu item, 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:

    • processEvent

      protected void processEvent(AWTEvent e)
      Processes events on this menu item. If the event is an instance of 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.

      Overrides:
      processEvent in class MenuComponent
      Parameters:
      e - the event
      Since:
      1.1
      See Also:

    • processActionEvent

      protected void processActionEvent(ActionEvent e)
      Processes action events occurring on this menu item, by dispatching them to any registered 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:
      • An ActionListener object is registered via addActionListener.
      • Action 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 action event
      Since:
      1.1
      See Also:

    • paramString

      public String paramString()
      Returns a string representing the state of this 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.
      Overrides:
      paramString in class MenuComponent
      Returns:
      the parameter string of this menu item

    • getAccessibleContext

      public AccessibleContext 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:
      getAccessibleContext in interface Accessible
      Overrides:
      getAccessibleContext in class MenuComponent
      Returns:
      an AccessibleAWTMenuItem that serves as the AccessibleContext of this MenuItem
      Since:
      1.3