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- 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 interface Action extends ActionListener
TheActioninterface provides a useful extension to theActionListenerinterface in cases where the same functionality may be accessed by several controls.In addition to the
actionPerformedmethod defined by theActionListenerinterface, 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 subclassing
AbstractAction). TheActionobject 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 theActionobject'ssetEnabledmethod.Note that
Actionimplementations 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 Supporting
ActionMany of Swing's components have an
Actionproperty. When anActionis set on a component, the following things happen:- The
Actionis added as anActionListenerto the component. - The component configures some of its properties to match the
Action. - The component installs a
PropertyChangeListeneron theActionso that the component can change its properties to reflect changes in theAction's properties.
The following table describes the properties used by
Swingcomponents that supportActions. In the table, button refers to anyAbstractButtonsubclass, which includes not onlyJButtonbut also classes such asJMenuItem. Unless otherwise stated, anullproperty value in anAction(or aActionthat isnull) results in the button's corresponding property being set tonull.Supported Action properties Component Property Components Action Key Notes enabledAll The isEnabledmethodtoolTipTextAll SHORT_DESCRIPTIONactionCommandAll ACTION_COMMAND_KEYmnemonicAll buttons MNEMONIC_KEYA nullvalue orActionresults in the button'smnemonicproperty being set to'\0'.textAll buttons NAMEIf you do not want the text of the button to mirror that of the Action, set the propertyhideActionTexttotrue. IfhideActionTextistrue, setting theActionchanges the text of the button tonulland any changes toNAMEare ignored.hideActionTextis useful for tool bar buttons that typically only show anIcon.JToolBar.add(Action)sets the property totrueif theActionhas a non-nullvalue forLARGE_ICON_KEYorSMALL_ICON.displayedMnemonicIndexAll buttons DISPLAYED_MNEMONIC_INDEX_KEYIf the value of DISPLAYED_MNEMONIC_INDEX_KEYis beyond the bounds of the text, it is ignored. WhensetActionis called, if the value from theActionisnull, the displayed mnemonic index is not updated. In any subsequent changes toDISPLAYED_MNEMONIC_INDEX_KEY,nullis treated as -1.iconAll buttons except of JCheckBox,JToggleButtonandJRadioButton.either LARGE_ICON_KEYorSMALL_ICONThe JMenuItemsubclasses only useSMALL_ICON. All other buttons will useLARGE_ICON_KEY; if the value isnullthey useSMALL_ICON.acceleratorAll JMenuItemsubclasses, with the exception ofJMenu.ACCELERATOR_KEYselectedJToggleButton,JCheckBox,JRadioButton,JCheckBoxMenuItemandJRadioButtonMenuItemSELECTED_KEYComponents that honor this property only use the value if it is non-null. For example, if you set anActionthat has anullvalue forSELECTED_KEYon aJToggleButton, theJToggleButtonwill 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 theActionif theActionhas anon-nullvalue forSELECTED_KEY.
Components that honor this property keep their selected state in sync with this property. When the sameActionis 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 sameActionthat defines a value for theSELECTED_KEYproperty with multiple mutually exclusive buttons.JPopupMenu,JToolBarandJMenuall provide convenience methods for creating a component and setting theActionon the corresponding component. Refer to each of these classes for more information.ActionusesPropertyChangeListenerto inform listeners theActionhas changed. The beans specification indicates that anullproperty name can be used to indicate multiple values have changed. By default Swing components that take anActiondo not handle such a change. To indicate that Swing should treatnullaccording to the beans specification set the system propertyswing.actions.reconfigureOnNullto theStringvaluetrue.- Since:
- 1.2
- See Also:
AbstractAction
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Field Summary
Fields Modifier and Type Field Description static StringACCELERATOR_KEYThe key used for storing aKeyStroketo be used as the accelerator for the action.static StringACTION_COMMAND_KEYThe key used to determine the commandStringfor theActionEventthat will be created when anActionis going to be notified as the result of residing in aKeymapassociated with aJComponent.static StringDEFAULTNot currently used.static StringDISPLAYED_MNEMONIC_INDEX_KEYThe key used for storing anIntegerthat corresponds to the index in the text (identified by theNAMEproperty) that the decoration for a mnemonic should be rendered at.static StringLARGE_ICON_KEYThe key used for storing anIcon.static StringLONG_DESCRIPTIONThe key used for storing a longerStringdescription for the action, could be used for context-sensitive help.static StringMNEMONIC_KEYThe key used for storing anIntegerthat corresponds to one of theKeyEventkey codes.static StringNAMEThe key used for storing theStringname for the action, used for a menu or button.static StringSELECTED_KEYThe key used for storing aBooleanthat corresponds to the selected state.static StringSHORT_DESCRIPTIONThe key used for storing a shortStringdescription for the action, used for tooltip text.static StringSMALL_ICONThe key used for storing a smallIcon, such asImageIcon.
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Method Summary
All Methods Instance Methods Abstract Methods Default Methods Modifier and Type Method Description default booleanaccept(Object sender)Determines whether the action should be performed with the specified sender object.voidaddPropertyChangeListener(PropertyChangeListener listener)Adds aPropertyChangelistener.ObjectgetValue(String key)Gets one of this object's properties using the associated key.booleanisEnabled()Returns the enabled state of theAction.voidputValue(String key, Object value)Sets one of this object's properties using the associated key.voidremovePropertyChangeListener(PropertyChangeListener listener)Removes aPropertyChangelistener.voidsetEnabled(boolean b)Sets the enabled state of theAction.-
Methods declared in interface java.awt.event.ActionListener
actionPerformed
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Field Detail
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DEFAULT
static final String DEFAULT
Not currently used.- See Also:
- Constant Field Values
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NAME
static final String NAME
The key used for storing theStringname for the action, used for a menu or button.- See Also:
- Constant Field Values
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SHORT_DESCRIPTION
static final String SHORT_DESCRIPTION
The key used for storing a shortStringdescription for the action, used for tooltip text.- See Also:
- Constant Field Values
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LONG_DESCRIPTION
static final String LONG_DESCRIPTION
The key used for storing a longerStringdescription for the action, could be used for context-sensitive help.- See Also:
- Constant Field Values
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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 same
Actionis used with menus and buttons you'll typically specify both aSMALL_ICONand aLARGE_ICON_KEY. The menu will use theSMALL_ICONand the button will use theLARGE_ICON_KEY.- See Also:
- Constant Field Values
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ACTION_COMMAND_KEY
static final String ACTION_COMMAND_KEY
The key used to determine the commandStringfor theActionEventthat will be created when anActionis going to be notified as the result of residing in aKeymapassociated with aJComponent.- See Also:
- Constant Field Values
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ACCELERATOR_KEY
static final String ACCELERATOR_KEY
The key used for storing aKeyStroketo be used as the accelerator for the action.- Since:
- 1.3
- See Also:
- Constant Field Values
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MNEMONIC_KEY
static final String MNEMONIC_KEY
The key used for storing anIntegerthat corresponds to one of theKeyEventkey codes. The value is commonly used to specify a mnemonic. For example:myAction.putValue(Action.MNEMONIC_KEY, KeyEvent.VK_A)sets the mnemonic ofmyActionto 'a', whilemyAction.putValue(Action.MNEMONIC_KEY, KeyEvent.getExtendedKeyCodeForChar('ф'))sets the mnemonic ofmyActionto Cyrillic letter "Ef".- Since:
- 1.3
- See Also:
- Constant Field Values
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SELECTED_KEY
static final String SELECTED_KEY
The key used for storing aBooleanthat corresponds to the selected state. This is typically used only for components that have a meaningful selection state. For example,JRadioButtonandJCheckBoxmake use of this but instances ofJMenudon't.This property differs from the others in that it is both read by the component and set by the component. For example, if an
Actionis attached to aJCheckBoxthe selected state of theJCheckBoxwill be set from that of theAction. If the user clicks on theJCheckBoxthe selected state of theJCheckBoxand theActionwill both be updated.Note: the value of this field is prefixed with 'Swing' to avoid possible collisions with existing
Actions.- Since:
- 1.6
- See Also:
- Constant Field Values
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DISPLAYED_MNEMONIC_INDEX_KEY
static final String DISPLAYED_MNEMONIC_INDEX_KEY
The key used for storing anIntegerthat corresponds to the index in the text (identified by theNAMEproperty) 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 existing
Actions.- Since:
- 1.6
- See Also:
AbstractButton.setDisplayedMnemonicIndex(int), Constant Field Values
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LARGE_ICON_KEY
static final String LARGE_ICON_KEY
The key used for storing anIcon. This is typically used by buttons, such asJButtonandJToggleButton.If the same
Actionis used with menus and buttons you'll typically specify both aSMALL_ICONand aLARGE_ICON_KEY. The menu will use theSMALL_ICONand the button theLARGE_ICON_KEY.Note: the value of this field is prefixed with 'Swing' to avoid possible collisions with existing
Actions.- Since:
- 1.6
- See Also:
- Constant Field Values
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Method Detail
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getValue
Object getValue(String key)
Gets one of this object's properties using the associated key.- Parameters:
key- aStringcontaining the key- Returns:
- the
Objectvalue - See Also:
putValue(java.lang.String, java.lang.Object)
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putValue
void putValue(String key, Object value)
Sets one of this object's properties using the associated key. If the value has changed, aPropertyChangeEventis sent to listeners.- Parameters:
key- aStringcontaining the keyvalue- anObjectvalue
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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'sactionPerformedmethod. If the value has changed, aPropertyChangeEventis sent to listeners.- Parameters:
b- true to enable thisAction, false to disable it- See Also:
accept(java.lang.Object)
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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'sactionPerformedmethod.- Returns:
- true if this
Actionis enabled - See Also:
accept(java.lang.Object)
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accept
default boolean accept(Object sender)
Determines whether the action should be performed with the specified sender object. Thesendercan benull. The method must return false if the action is disabled.- Parameters:
sender- the object to check, can be null- Returns:
trueif the action should be performed with the sender object, must be false if the action is disabled.- See Also:
isEnabled(),setEnabled(boolean)
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addPropertyChangeListener
void addPropertyChangeListener(PropertyChangeListener listener)
Adds aPropertyChangelistener. Containers and attached components use these methods to register interest in thisActionobject. When its enabled state or other property changes, the registered listeners are informed of the change.- Parameters:
listener- aPropertyChangeListenerobject
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removePropertyChangeListener
void removePropertyChangeListener(PropertyChangeListener listener)
Removes aPropertyChangelistener.- Parameters:
listener- aPropertyChangeListenerobject- See Also:
addPropertyChangeListener(java.beans.PropertyChangeListener)
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