JMenuItem (Java 2 Platform SE 5.0) - JDK 5 Documentation v1.5.0, Java 2 SDK 英文文档

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Java^TM 2 Platform
Standard Ed. 5.0

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javax.swing
Class JMenuItem

java.lang.Object
  java.awt.Component
      java.awt.Container
          javax.swing.JComponent
              javax.swing.AbstractButton
                  javax.swing.JMenuItem

All Implemented Interfaces:: ImageObserver, ItemSelectable, MenuContainer, Serializable, Accessible, MenuElement, SwingConstants

Direct Known Subclasses:: JCheckBoxMenuItem, JMenu, JRadioButtonMenuItem

public class JMenuItem
extends AbstractButton
implements Accessible, MenuElement
extends AbstractButton
implements Accessible, MenuElement

An implementation of an item in a menu. A menu item is essentially a button sitting in a list. When the user selects the "button", the action associated with the menu item is performed. A JMenuItem contained in a JPopupMenu performs exactly that function.

For further documentation and for examples, see How to Use Menus in The Java Tutorial.

Warning: Serialized objects of this class will not be compatible with future Swing releases. The current serialization support is appropriate for short term storage or RMI between applications running the same version of Swing. As of 1.4, support for long term storage of all JavaBeans^TM has been added to the java.beans package. Please see XMLEncoder.

See Also:: JPopupMenu, JMenu, JCheckBoxMenuItem, JRadioButtonMenuItem

Nested Class Summary
`protected class`	`JMenuItem.AccessibleJMenuItem` This class implements accessibility support for the `JMenuItem` class.

Nested classes/interfaces inherited from class javax.swing.AbstractButton
`AbstractButton.AccessibleAbstractButton, AbstractButton.ButtonChangeListener`

Nested classes/interfaces inherited from class javax.swing.JComponent
`JComponent.AccessibleJComponent`

Nested classes/interfaces inherited from class java.awt.Container
`Container.AccessibleAWTContainer`

Nested classes/interfaces inherited from class java.awt.Component
`Component.AccessibleAWTComponent, Component.BltBufferStrategy, Component.FlipBufferStrategy`

Fields inherited from class javax.swing.AbstractButton
actionListener, BORDER_PAINTED_CHANGED_PROPERTY, changeEvent, changeListener, CONTENT_AREA_FILLED_CHANGED_PROPERTY, DISABLED_ICON_CHANGED_PROPERTY, DISABLED_SELECTED_ICON_CHANGED_PROPERTY, FOCUS_PAINTED_CHANGED_PROPERTY, HORIZONTAL_ALIGNMENT_CHANGED_PROPERTY, HORIZONTAL_TEXT_POSITION_CHANGED_PROPERTY, ICON_CHANGED_PROPERTY, itemListener, MARGIN_CHANGED_PROPERTY, MNEMONIC_CHANGED_PROPERTY, model, MODEL_CHANGED_PROPERTY, PRESSED_ICON_CHANGED_PROPERTY, ROLLOVER_ENABLED_CHANGED_PROPERTY, ROLLOVER_ICON_CHANGED_PROPERTY, ROLLOVER_SELECTED_ICON_CHANGED_PROPERTY, SELECTED_ICON_CHANGED_PROPERTY, TEXT_CHANGED_PROPERTY, VERTICAL_ALIGNMENT_CHANGED_PROPERTY, VERTICAL_TEXT_POSITION_CHANGED_PROPERTY

Fields inherited from class javax.swing.JComponent
`accessibleContext, listenerList, TOOL_TIP_TEXT_KEY, ui, UNDEFINED_CONDITION, WHEN_ANCESTOR_OF_FOCUSED_COMPONENT, WHEN_FOCUSED, WHEN_IN_FOCUSED_WINDOW`

Fields inherited from class java.awt.Component
`BOTTOM_ALIGNMENT, CENTER_ALIGNMENT, LEFT_ALIGNMENT, RIGHT_ALIGNMENT, TOP_ALIGNMENT`

Fields inherited from interface javax.swing.SwingConstants
`BOTTOM, CENTER, EAST, HORIZONTAL, LEADING, LEFT, NEXT, NORTH, NORTH_EAST, NORTH_WEST, PREVIOUS, RIGHT, SOUTH, SOUTH_EAST, SOUTH_WEST, TOP, TRAILING, VERTICAL, WEST`

Fields inherited from interface java.awt.image.ImageObserver
`ABORT, ALLBITS, ERROR, FRAMEBITS, HEIGHT, PROPERTIES, SOMEBITS, WIDTH`

Constructor Summary
`JMenuItem()` Creates a `JMenuItem` with no set text or icon.
`JMenuItem(Action a)` Creates a menu item whose properties are taken from the specified `Action`.
`JMenuItem(Icon icon)` Creates a `JMenuItem` with the specified icon.
`JMenuItem(String text)` Creates a `JMenuItem` with the specified text.
`JMenuItem(String text, Icon icon)` Creates a `JMenuItem` with the specified text and icon.
`JMenuItem(String text, int mnemonic)` Creates a `JMenuItem` with the specified text and keyboard mnemonic.

Method Summary
`void`	`addMenuDragMouseListener(MenuDragMouseListener l)` Adds a `MenuDragMouseListener` to the menu item.
`void`	`addMenuKeyListener(MenuKeyListener l)` Adds a `MenuKeyListener` to the menu item.
`protected void`	`configurePropertiesFromAction(Action a)` Factory method which sets the `ActionEvent` source's properties according to values from the `Action` instance.
`protected PropertyChangeListener`	`createActionPropertyChangeListener(Action a)` Factory method which creates the `PropertyChangeListener` used to update the `ActionEvent` source as properties change on its `Action` instance.
`protected void`	`fireMenuDragMouseDragged(MenuDragMouseEvent event)` Notifies all listeners that have registered interest for notification on this event type.
`protected void`	`fireMenuDragMouseEntered(MenuDragMouseEvent event)` Notifies all listeners that have registered interest for notification on this event type.
`protected void`	`fireMenuDragMouseExited(MenuDragMouseEvent event)` Notifies all listeners that have registered interest for notification on this event type.
`protected void`	`fireMenuDragMouseReleased(MenuDragMouseEvent event)` Notifies all listeners that have registered interest for notification on this event type.
`protected void`	`fireMenuKeyPressed(MenuKeyEvent event)` Notifies all listeners that have registered interest for notification on this event type.
`protected void`	`fireMenuKeyReleased(MenuKeyEvent event)` Notifies all listeners that have registered interest for notification on this event type.
`protected void`	`fireMenuKeyTyped(MenuKeyEvent event)` Notifies all listeners that have registered interest for notification on this event type.
`KeyStroke`	`getAccelerator()` Returns the `KeyStroke` which serves as an accelerator for the menu item.
`AccessibleContext`	`getAccessibleContext()` Returns the `AccessibleContext` associated with this `JMenuItem`.
`Component`	`getComponent()` Returns the `java.awt.Component` used to paint this object.
`MenuDragMouseListener[]`	`getMenuDragMouseListeners()` Returns an array of all the `MenuDragMouseListener`s added to this JMenuItem with addMenuDragMouseListener().
`MenuKeyListener[]`	`getMenuKeyListeners()` Returns an array of all the `MenuKeyListener`s added to this JMenuItem with addMenuKeyListener().
`MenuElement[]`	`getSubElements()` This method returns an array containing the sub-menu components for this menu component.
`String`	`getUIClassID()` Returns the suffix used to construct the name of the L&F class used to render this component.
`protected void`	`init(String text, Icon icon)` Initializes the menu item with the specified text and icon.
`boolean`	`isArmed()` Returns whether the menu item is "armed".
`void`	`menuSelectionChanged(boolean isIncluded)` Called by the `MenuSelectionManager` when the `MenuElement` is selected or unselected.
`protected String`	`paramString()` Returns a string representation of this `JMenuItem`.
`void`	`processKeyEvent(KeyEvent e, MenuElement[] path, MenuSelectionManager manager)` Processes a key event forwarded from the `MenuSelectionManager` and changes the menu selection, if necessary, by using `MenuSelectionManager`'s API.
`void`	`processMenuDragMouseEvent(MenuDragMouseEvent e)` Handles mouse drag in a menu.
`void`	`processMenuKeyEvent(MenuKeyEvent e)` Handles a keystroke in a menu.
`void`	`processMouseEvent(MouseEvent e, MenuElement[] path, MenuSelectionManager manager)` Processes a mouse event forwarded from the `MenuSelectionManager` and changes the menu selection, if necessary, by using the `MenuSelectionManager`'s API.
`void`	`removeMenuDragMouseListener(MenuDragMouseListener l)` Removes a `MenuDragMouseListener` from the menu item.
`void`	`removeMenuKeyListener(MenuKeyListener l)` Removes a `MenuKeyListener` from the menu item.
`void`	`setAccelerator(KeyStroke keyStroke)` Sets the key combination which invokes the menu item's action listeners without navigating the menu hierarchy.
`void`	`setArmed(boolean b)` Identifies the menu item as "armed".
`void`	`setEnabled(boolean b)` Enables or disables the menu item.
`void`	`setUI(MenuItemUI ui)` Sets the look and feel object that renders this component.
`void`	`updateUI()` Resets the UI property with a value from the current look and feel.

Methods inherited from class javax.swing.AbstractButton
addActionListener, addChangeListener, addImpl, addItemListener, checkHorizontalKey, checkVerticalKey, createActionListener, createChangeListener, createItemListener, doClick, doClick, fireActionPerformed, fireItemStateChanged, fireStateChanged, getAction, getActionCommand, getActionListeners, getChangeListeners, getDisabledIcon, getDisabledSelectedIcon, getDisplayedMnemonicIndex, getHorizontalAlignment, getHorizontalTextPosition, getIcon, getIconTextGap, getItemListeners, getLabel, getMargin, getMnemonic, getModel, getMultiClickThreshhold, getPressedIcon, getRolloverIcon, getRolloverSelectedIcon, getSelectedIcon, getSelectedObjects, getText, getUI, getVerticalAlignment, getVerticalTextPosition, imageUpdate, isBorderPainted, isContentAreaFilled, isFocusPainted, isRolloverEnabled, isSelected, paintBorder, removeActionListener, removeChangeListener, removeItemListener, setAction, setActionCommand, setBorderPainted, setContentAreaFilled, setDisabledIcon, setDisabledSelectedIcon, setDisplayedMnemonicIndex, setFocusPainted, setHorizontalAlignment, setHorizontalTextPosition, setIcon, setIconTextGap, setLabel, setLayout, setMargin, setMnemonic, setMnemonic, setModel, setMultiClickThreshhold, setPressedIcon, setRolloverEnabled, setRolloverIcon, setRolloverSelectedIcon, setSelected, setSelectedIcon, setText, setUI, setVerticalAlignment, setVerticalTextPosition

Methods inherited from class javax.swing.JComponent
addAncestorListener, addNotify, addVetoableChangeListener, computeVisibleRect, contains, createToolTip, disable, enable, firePropertyChange, firePropertyChange, firePropertyChange, fireVetoableChange, getActionForKeyStroke, getActionMap, getAlignmentX, getAlignmentY, getAncestorListeners, getAutoscrolls, getBorder, getBounds, getClientProperty, getComponentGraphics, getComponentPopupMenu, getConditionForKeyStroke, getDebugGraphicsOptions, getDefaultLocale, getFontMetrics, getGraphics, getHeight, getInheritsPopupMenu, getInputMap, getInputMap, getInputVerifier, getInsets, getInsets, getListeners, getLocation, getMaximumSize, getMinimumSize, getNextFocusableComponent, getPopupLocation, getPreferredSize, getRegisteredKeyStrokes, getRootPane, getSize, getToolTipLocation, getToolTipText, getToolTipText, getTopLevelAncestor, getTransferHandler, getVerifyInputWhenFocusTarget, getVetoableChangeListeners, getVisibleRect, getWidth, getX, getY, grabFocus, isDoubleBuffered, isLightweightComponent, isManagingFocus, isOpaque, isOptimizedDrawingEnabled, isPaintingTile, isRequestFocusEnabled, isValidateRoot, paint, paintChildren, paintComponent, paintImmediately, paintImmediately, print, printAll, printBorder, printChildren, printComponent, processComponentKeyEvent, processKeyBinding, processKeyEvent, processMouseEvent, processMouseMotionEvent, putClientProperty, registerKeyboardAction, registerKeyboardAction, removeAncestorListener, removeNotify, removeVetoableChangeListener, repaint, repaint, requestDefaultFocus, requestFocus, requestFocus, requestFocusInWindow, requestFocusInWindow, resetKeyboardActions, reshape, revalidate, scrollRectToVisible, setActionMap, setAlignmentX, setAlignmentY, setAutoscrolls, setBackground, setBorder, setComponentPopupMenu, setDebugGraphicsOptions, setDefaultLocale, setDoubleBuffered, setFocusTraversalKeys, setFont, setForeground, setInheritsPopupMenu, setInputMap, setInputVerifier, setMaximumSize, setMinimumSize, setNextFocusableComponent, setOpaque, setPreferredSize, setRequestFocusEnabled, setToolTipText, setTransferHandler, setUI, setVerifyInputWhenFocusTarget, setVisible, unregisterKeyboardAction, update

Methods inherited from class java.awt.Container
add, add, add, add, add, addContainerListener, addPropertyChangeListener, addPropertyChangeListener, applyComponentOrientation, areFocusTraversalKeysSet, countComponents, deliverEvent, doLayout, findComponentAt, findComponentAt, getComponent, getComponentAt, getComponentAt, getComponentCount, getComponents, getComponentZOrder, getContainerListeners, getFocusTraversalKeys, getFocusTraversalPolicy, getLayout, getMousePosition, insets, invalidate, isAncestorOf, isFocusCycleRoot, isFocusCycleRoot, isFocusTraversalPolicyProvider, isFocusTraversalPolicySet, layout, list, list, locate, minimumSize, paintComponents, preferredSize, printComponents, processContainerEvent, processEvent, remove, remove, removeAll, removeContainerListener, setComponentZOrder, setFocusCycleRoot, setFocusTraversalPolicy, setFocusTraversalPolicyProvider, transferFocusBackward, transferFocusDownCycle, validate, validateTree

Methods inherited from class java.awt.Component
action, add, addComponentListener, addFocusListener, addHierarchyBoundsListener, addHierarchyListener, addInputMethodListener, addKeyListener, addMouseListener, addMouseMotionListener, addMouseWheelListener, bounds, checkImage, checkImage, coalesceEvents, contains, createImage, createImage, createVolatileImage, createVolatileImage, disableEvents, dispatchEvent, enable, enableEvents, enableInputMethods, firePropertyChange, firePropertyChange, firePropertyChange, firePropertyChange, firePropertyChange, firePropertyChange, getBackground, getBounds, getColorModel, getComponentListeners, getComponentOrientation, getCursor, getDropTarget, getFocusCycleRootAncestor, getFocusListeners, getFocusTraversalKeysEnabled, getFont, getForeground, getGraphicsConfiguration, getHierarchyBoundsListeners, getHierarchyListeners, getIgnoreRepaint, getInputContext, getInputMethodListeners, getInputMethodRequests, getKeyListeners, getLocale, getLocation, getLocationOnScreen, getMouseListeners, getMouseMotionListeners, getMousePosition, getMouseWheelListeners, getName, getParent, getPeer, getPropertyChangeListeners, getPropertyChangeListeners, getSize, getToolkit, getTreeLock, gotFocus, handleEvent, hasFocus, hide, inside, isBackgroundSet, isCursorSet, isDisplayable, isEnabled, isFocusable, isFocusOwner, isFocusTraversable, isFontSet, isForegroundSet, isLightweight, isMaximumSizeSet, isMinimumSizeSet, isPreferredSizeSet, isShowing, isValid, isVisible, keyDown, keyUp, list, list, list, location, lostFocus, mouseDown, mouseDrag, mouseEnter, mouseExit, mouseMove, mouseUp, move, nextFocus, paintAll, postEvent, prepareImage, prepareImage, processComponentEvent, processFocusEvent, processHierarchyBoundsEvent, processHierarchyEvent, processInputMethodEvent, processMouseWheelEvent, remove, removeComponentListener, removeFocusListener, removeHierarchyBoundsListener, removeHierarchyListener, removeInputMethodListener, removeKeyListener, removeMouseListener, removeMouseMotionListener, removeMouseWheelListener, removePropertyChangeListener, removePropertyChangeListener, repaint, repaint, repaint, resize, resize, setBounds, setBounds, setComponentOrientation, setCursor, setDropTarget, setFocusable, setFocusTraversalKeysEnabled, setIgnoreRepaint, setLocale, setLocation, setLocation, setName, setSize, setSize, show, show, size, toString, transferFocus, transferFocusUpCycle

Methods inherited from class java.lang.Object
`clone, equals, finalize, getClass, hashCode, notify, notifyAll, wait, wait, wait`

Constructor Detail

JMenuItem

public JMenuItem()

Creates a JMenuItem with no set text or icon.

JMenuItem

public JMenuItem(Icon icon)

Creates a JMenuItem with the specified icon.

Parameters:: icon - the icon of the JMenuItem

JMenuItem

public JMenuItem(String text)

Creates a JMenuItem with the specified text.

Parameters:: text - the text of the JMenuItem

JMenuItem

public JMenuItem(Action a)

Creates a menu item whose properties are taken from the specified Action.

Parameters:: a - the action of the JMenuItem
Since:: 1.3

JMenuItem

public JMenuItem(String text,
                 Icon icon)

Creates a JMenuItem with the specified text and icon.

Parameters:: text - the text of the JMenuItem; icon - the icon of the JMenuItem

JMenuItem

public JMenuItem(String text,
                 int mnemonic)

Creates a JMenuItem with the specified text and keyboard mnemonic.

Parameters:: text - the text of the JMenuItem; mnemonic - the keyboard mnemonic for the JMenuItem

Method Detail

init

protected void init(String text,
                    Icon icon)

Initializes the menu item with the specified text and icon.

Overrides:: init in class AbstractButton

Parameters:: text - the text of the JMenuItem; icon - the icon of the JMenuItem

setUI

public void setUI(MenuItemUI ui)

Sets the look and feel object that renders this component.

Parameters:: ui - the JMenuItemUI L&F object
See Also:: UIDefaults.getUI(javax.swing.JComponent)

updateUI

public void updateUI()

Resets the UI property with a value from the current look and feel.

Overrides:: updateUI in class AbstractButton

See Also:: JComponent.updateUI()

getUIClassID

public String getUIClassID()

Returns the suffix used to construct the name of the L&F class used to render this component.

Overrides:: getUIClassID in class JComponent

Returns:: the string "MenuItemUI"
See Also:: JComponent.getUIClassID(), UIDefaults.getUI(javax.swing.JComponent)

setArmed

public void setArmed(boolean b)

Identifies the menu item as "armed". If the mouse button is released while it is over this item, the menu's action event will fire. If the mouse button is released elsewhere, the event will not fire and the menu item will be disarmed.

Parameters:: b - true to arm the menu item so it can be selected

isArmed

public boolean isArmed()

Returns whether the menu item is "armed".

Returns:: true if the menu item is armed, and it can be selected
See Also:: setArmed(boolean)

setEnabled

public void setEnabled(boolean b)

Enables or disables the menu item.

Overrides:: setEnabled in class AbstractButton

Parameters:: b - true to enable the item
See Also:: Component.isEnabled(), Component.isLightweight()

setAccelerator

public void setAccelerator(KeyStroke keyStroke)

Sets the key combination which invokes the menu item's action listeners without navigating the menu hierarchy. It is the UI's responsibility to install the correct action. Note that when the keyboard accelerator is typed, it will work whether or not the menu is currently displayed.

Parameters:: keyStroke - the KeyStroke which will serve as an accelerator

getAccelerator

public KeyStroke getAccelerator()

Returns the KeyStroke which serves as an accelerator for the menu item.

Returns:: a KeyStroke object identifying the accelerator key

configurePropertiesFromAction

protected void configurePropertiesFromAction(Action a)

Factory method which sets the ActionEvent source's properties according to values from the Action instance. The properties which are set may differ for subclasses. By default, this method sets the same properties as AbstractButton.configurePropertiesFromAction(), plus Accelerator.

Overrides:: configurePropertiesFromAction in class AbstractButton

Parameters:: a - the Action from which to get the properties, or null
Since:: 1.3
See Also:: Action

createActionPropertyChangeListener

protected PropertyChangeListener createActionPropertyChangeListener(Action a)

Factory method which creates the PropertyChangeListener used to update the ActionEvent source as properties change on its Action instance. Subclasses may override this in order to provide their own PropertyChangeListener if the set of properties which should be kept up to date differs.

Note that PropertyChangeListeners should avoid holding strong references to the ActionEvent source, as this may hinder garbage collection of the ActionEvent source and all components in its containment hierarchy.

Overrides:: createActionPropertyChangeListener in class AbstractButton

Parameters:: a - the Action from which to get the properties, or null
Since:: 1.3
See Also:: Action

processMouseEvent

public void processMouseEvent(MouseEvent e,
                              MenuElement[] path,
                              MenuSelectionManager manager)

Processes a mouse event forwarded from the MenuSelectionManager and changes the menu selection, if necessary, by using the MenuSelectionManager's API.

Note: you do not have to forward the event to sub-components. This is done automatically by the MenuSelectionManager.

Specified by:: processMouseEvent in interface MenuElement

Parameters:: e - a MouseEvent; path - the MenuElement path array; manager - the MenuSelectionManager

processKeyEvent

public void processKeyEvent(KeyEvent e,
                            MenuElement[] path,
                            MenuSelectionManager manager)

Processes a key event forwarded from the MenuSelectionManager and changes the menu selection, if necessary, by using MenuSelectionManager's API.

Note: you do not have to forward the event to sub-components. This is done automatically by the MenuSelectionManager.

Specified by:: processKeyEvent in interface MenuElement

Parameters:: e - a KeyEvent; path - the MenuElement path array; manager - the MenuSelectionManager

processMenuDragMouseEvent

public void processMenuDragMouseEvent(MenuDragMouseEvent e)

Handles mouse drag in a menu.

Parameters:: e - a MenuDragMouseEvent object

processMenuKeyEvent

public void processMenuKeyEvent(MenuKeyEvent e)

Handles a keystroke in a menu.

Parameters:: e - a MenuKeyEvent object