Interface Action

All Superinterfaces:
ActionListener,EventListener
All Known Implementing Classes:
AbstractAction,BasicDesktopPaneUI.CloseAction,BasicDesktopPaneUI.MaximizeAction,BasicDesktopPaneUI.MinimizeAction,BasicDesktopPaneUI.NavigateAction,BasicDesktopPaneUI.OpenAction,BasicFileChooserUI.ApproveSelectionAction,BasicFileChooserUI.CancelSelectionAction,BasicFileChooserUI.ChangeToParentDirectoryAction,BasicFileChooserUI.GoHomeAction,BasicFileChooserUI.NewFolderAction,BasicFileChooserUI.UpdateAction,BasicInternalFrameTitlePane.CloseAction,BasicInternalFrameTitlePane.IconifyAction,BasicInternalFrameTitlePane.MaximizeAction,BasicInternalFrameTitlePane.MoveAction,BasicInternalFrameTitlePane.RestoreAction,BasicInternalFrameTitlePane.SizeAction,BasicSliderUI.ActionScroller,BasicTreeUI.TreeCancelEditingAction,BasicTreeUI.TreeHomeAction,BasicTreeUI.TreeIncrementAction,BasicTreeUI.TreePageAction,BasicTreeUI.TreeToggleAction,BasicTreeUI.TreeTraverseAction,DefaultEditorKit.BeepAction,DefaultEditorKit.CopyAction,DefaultEditorKit.CutAction,DefaultEditorKit.DefaultKeyTypedAction,DefaultEditorKit.InsertBreakAction,DefaultEditorKit.InsertContentAction,DefaultEditorKit.InsertTabAction,DefaultEditorKit.PasteAction,HTMLEditorKit.HTMLTextAction,HTMLEditorKit.InsertHTMLTextAction,MetalFileChooserUI.DirectoryComboBoxAction,StyledEditorKit.AlignmentAction,StyledEditorKit.BoldAction,StyledEditorKit.FontFamilyAction,StyledEditorKit.FontSizeAction,StyledEditorKit.ForegroundAction,StyledEditorKit.ItalicAction,StyledEditorKit.StyledTextAction,StyledEditorKit.UnderlineAction,TextAction
public interfaceActionextendsActionListener
TheAction interface provides a useful extension to theActionListener interface in cases where the same functionality may be accessed by several controls.

In addition to theactionPerformed method defined by theActionListener interface, this interface allows the application to define, in a single place:

  • One or more text strings that describe the function. These strings can be used, for example, to display the flyover text for a button or to set the text in a menu item.
  • One or more icons that depict the function. These icons can be used for the images in a menu control, or for composite entries in a more sophisticated user interface.
  • The enabled/disabled state of the functionality. Instead of having to separately disable the menu item and the toolbar button, the application can disable the function that implements this interface. All components which are registered as listeners for the state change then know to disable event generation for that item and to modify the display accordingly.

This interface can be added to an existing class or used to create an adapter (typically, by subclassingAbstractAction). TheAction object can then be added to multipleAction-aware containers and connected toAction-capable components. The GUI controls can then be activated or deactivated all at once by invoking theAction object'ssetEnabled method.

Note thatAction implementations tend to be more expensive in terms of storage than a typicalActionListener, which does not offer the benefits of centralized control of functionality and broadcast of property changes. For this reason, you should take care to only useActions where their benefits are desired, and use simpleActionListeners elsewhere.

Swing Components SupportingAction

Many of Swing's components have anAction property. When anAction is set on a component, the following things happen:

  • TheAction is added as anActionListener to the component.
  • The component configures some of its properties to match theAction.
  • The component installs aPropertyChangeListener on theAction so that the component can change its properties to reflect changes in theAction's properties.

The following table describes the properties used bySwing components that supportActions. In the table,button refers to anyAbstractButton subclass, which includes not onlyJButton but also classes such asJMenuItem. Unless otherwise stated, anull property value in anAction (or aAction that isnull) results in the button's corresponding property being set tonull.

Supported Action properties
Component PropertyComponentsAction KeyNotes
enabledAllTheisEnabled method 
toolTipTextAllSHORT_DESCRIPTION 
actionCommandAllACTION_COMMAND_KEY 
mnemonicAll buttonsMNEMONIC_KEYAnull value orAction results in the button'smnemonic property being set to'\0'.
textAll buttonsNAMEIf you do not want the text of the button to mirror that of theAction, set the propertyhideActionText totrue. IfhideActionText istrue, setting theAction changes the text of the button tonull and any changes toNAME are ignored.hideActionText is useful for tool bar buttons that typically only show anIcon.JToolBar.add(Action) sets the property totrue if theAction has a non-null value forLARGE_ICON_KEY orSMALL_ICON.
displayedMnemonicIndexAll buttonsDISPLAYED_MNEMONIC_INDEX_KEYIf the value ofDISPLAYED_MNEMONIC_INDEX_KEY is beyond the bounds of the text, it is ignored. WhensetAction is called, if the value from theAction isnull, the displayed mnemonic index is not updated. In any subsequent changes toDISPLAYED_MNEMONIC_INDEX_KEY,null is treated as -1.
iconAll buttons except ofJCheckBox,JToggleButton andJRadioButton.eitherLARGE_ICON_KEY orSMALL_ICONTheJMenuItem subclasses only useSMALL_ICON. All other buttons will useLARGE_ICON_KEY; if the value isnull they useSMALL_ICON.
acceleratorAllJMenuItem subclasses, with the exception ofJMenu.ACCELERATOR_KEY 
selectedJToggleButton,JCheckBox,JRadioButton,JCheckBoxMenuItem andJRadioButtonMenuItemSELECTED_KEYComponents that honor this property only use the value if it isnon-null. For example, if you set anAction that has anull value forSELECTED_KEY on aJToggleButton, theJToggleButton will not update it's selected state in any way. Similarly, any time theJToggleButton's selected state changes it will only set the value back on theAction if theAction has anon-null value forSELECTED_KEY.
Components that honor this property keep their selected state in sync with this property. When the sameAction is used with multiple components, all the components keep their selected state in sync with this property. Mutually exclusive buttons, such asJToggleButtons in aButtonGroup, force only one of the buttons to be selected. As such, do not use the sameAction that defines a value for theSELECTED_KEY property with multiple mutually exclusive buttons.

JPopupMenu,JToolBar andJMenu all provide convenience methods for creating a component and setting theAction on the corresponding component. Refer to each of these classes for more information.

Action usesPropertyChangeListener to inform listeners theAction has changed. The beans specification indicates that anull property name can be used to indicate multiple values have changed. By default Swing components that take anAction do not handle such a change. To indicate that Swing should treatnull according to the beans specification set the system propertyswing.actions.reconfigureOnNull to theString valuetrue.

Since:
1.2
See Also:

  • Field Summary

    Fields
    Modifier and Type
    Field
    Description
    static finalString
    The key used for storing aKeyStroke to be used as the accelerator for the action.
    static finalString
    The key used to determine the commandString for theActionEvent that will be created when anAction is going to be notified as the result of residing in aKeymap associated with aJComponent.
    static finalString
    Not currently used.
    static finalString
    The key used for storing anInteger that corresponds to the index in the text (identified by theNAME property) that the decoration for a mnemonic should be rendered at.
    static finalString
    The key used for storing anIcon.
    static finalString
    The key used for storing a longerString description for the action, could be used for context-sensitive help.
    static finalString
    The key used for storing anInteger that corresponds to one of theKeyEvent key codes.
    static finalString
    The key used for storing theString name for the action, used for a menu or button.
    static finalString
    The key used for storing aBoolean that corresponds to the selected state.
    static finalString
    The key used for storing a shortString description for the action, used for tooltip text.
    static finalString
    The key used for storing a smallIcon, such asImageIcon.

  • Method Summary

    Modifier and Type
    Method
    Description
    default boolean
    accept(Object sender)
    Determines whether the action should be performed with the specified sender object.
    void
    Adds aPropertyChange listener.
    Gets one of this object's properties using the associated key.
    boolean
    Returns the enabled state of theAction.
    void
    putValue(String key,Object value)
    Sets one of this object's properties using the associated key.
    void
    Removes aPropertyChange listener.
    void
    setEnabled(boolean b)
    Sets the enabled state of theAction.

    Methods declared in interface java.awt.event.ActionListener

    actionPerformed

  • Field Details

    • DEFAULT

      static final String DEFAULT
      Not currently used.
      See Also:

    • NAME

      static final String NAME
      The key used for storing theString name for the action, used for a menu or button.
      See Also:

    • SHORT_DESCRIPTION

      static final String SHORT_DESCRIPTION
      The key used for storing a shortString description for the action, used for tooltip text.
      See Also:

    • LONG_DESCRIPTION

      static final String LONG_DESCRIPTION
      The key used for storing a longerString description for the action, could be used for context-sensitive help.
      See Also:

    • SMALL_ICON

      static final String SMALL_ICON
      The key used for storing a smallIcon, such asImageIcon. This is typically used with menus such asJMenuItem.

      If the sameAction is used with menus and buttons you'll typically specify both aSMALL_ICON and aLARGE_ICON_KEY. The menu will use theSMALL_ICON and the button will use theLARGE_ICON_KEY.

      See Also:

    • ACTION_COMMAND_KEY

      static final String ACTION_COMMAND_KEY
      The key used to determine the commandString for theActionEvent that will be created when anAction is going to be notified as the result of residing in aKeymap associated with aJComponent.
      See Also:

    • ACCELERATOR_KEY

      static final String ACCELERATOR_KEY
      The key used for storing aKeyStroke to be used as the accelerator for the action.
      Since:
      1.3
      See Also:

    • MNEMONIC_KEY

      static final String MNEMONIC_KEY
      The key used for storing anInteger that corresponds to one of theKeyEvent key codes. The value is commonly used to specify a mnemonic. For example:myAction.putValue(Action.MNEMONIC_KEY, KeyEvent.VK_A) sets the mnemonic ofmyAction to 'a', whilemyAction.putValue(Action.MNEMONIC_KEY, KeyEvent.getExtendedKeyCodeForChar('ф')) sets the mnemonic ofmyAction to Cyrillic letter "Ef".
      Since:
      1.3
      See Also:

    • SELECTED_KEY

      static final String SELECTED_KEY
      The key used for storing aBoolean that corresponds to the selected state. This is typically used only for components that have a meaningful selection state. For example,JRadioButton andJCheckBox make use of this but instances ofJMenu don't.

      This property differs from the others in that it is both read by the component and set by the component. For example, if anAction is attached to aJCheckBox the selected state of theJCheckBox will be set from that of theAction. If the user clicks on theJCheckBox the selected state of theJCheckBoxand theAction willboth be updated.

      Note: the value of this field is prefixed with 'Swing' to avoid possible collisions with existingActions.

      Since:
      1.6
      See Also:

    • DISPLAYED_MNEMONIC_INDEX_KEY

      static final String DISPLAYED_MNEMONIC_INDEX_KEY
      The key used for storing anInteger that corresponds to the index in the text (identified by theNAME property) that the decoration for a mnemonic should be rendered at. If the value of this property is greater than or equal to the length of the text, it will treated as -1.

      Note: the value of this field is prefixed with 'Swing' to avoid possible collisions with existingActions.

      Since:
      1.6
      See Also:

    • LARGE_ICON_KEY

      static final String LARGE_ICON_KEY
      The key used for storing anIcon. This is typically used by buttons, such asJButton andJToggleButton.

      If the sameAction is used with menus and buttons you'll typically specify both aSMALL_ICON and aLARGE_ICON_KEY. The menu will use theSMALL_ICON and the button theLARGE_ICON_KEY.

      Note: the value of this field is prefixed with 'Swing' to avoid possible collisions with existingActions.

      Since:
      1.6
      See Also:

  • Method Details

    • getValue

      Object getValue(String key)
      Gets one of this object's properties using the associated key.
      Parameters:
      key - aString containing the key
      Returns:
      theObject value
      See Also:

    • putValue

      void putValue(String key,Object value)
      Sets one of this object's properties using the associated key. If the value has changed, aPropertyChangeEvent is sent to listeners.
      Parameters:
      key - aString containing the key
      value - anObject value

    • setEnabled

      void setEnabled(boolean b)
      Sets the enabled state of theAction. When enabled, any component associated with this object is active and able to fire this object'sactionPerformed method. If the value has changed, aPropertyChangeEvent is sent to listeners.
      Parameters:
      b - true to enable thisAction, false to disable it
      See Also:

    • isEnabled

      boolean isEnabled()
      Returns the enabled state of theAction. When enabled, any component associated with this object is active and able to fire this object'sactionPerformed method.
      Returns:
      true if thisAction is enabled
      See Also:

    • accept

      default boolean accept(Object sender)
      Determines whether the action should be performed with the specified sender object. Thesender can benull. The method must return false if the action is disabled.
      Parameters:
      sender - the object to check, can be null
      Returns:
      true if the action should be performed with the sender object, must be false if the action is disabled.
      See Also:

    • addPropertyChangeListener

      void addPropertyChangeListener(PropertyChangeListener listener)
      Adds aPropertyChange listener. Containers and attached components use these methods to register interest in thisAction object. When its enabled state or other property changes, the registered listeners are informed of the change.
      Parameters:
      listener - aPropertyChangeListener object

    • removePropertyChangeListener

      void removePropertyChangeListener(PropertyChangeListener listener)
      Removes aPropertyChange listener.
      Parameters:
      listener - aPropertyChangeListener object
      See Also: