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 interface Action extends ActionListener
The Action
interface provides a useful extension to the ActionListener
interface in cases where the same functionality may be accessed by several controls.
In addition to the actionPerformed
method defined by the ActionListener
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 subclassing AbstractAction
). The Action
object can then be added to multiple Action
-aware containers and connected to Action
-capable components. The GUI controls can then be activated or deactivated all at once by invoking the Action
object's setEnabled
method.
Note that Action
implementations tend to be more expensive in terms of storage than a typical ActionListener
, 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 use Action
s where their benefits are desired, and use simple ActionListener
s elsewhere.
Swing Components Supporting Action
Many of Swing's components have an Action
property. When an Action
is set on a component, the following things happen:
- The
Action
is added as anActionListener
to the component. - The component configures some of its properties to match the
Action
. - The component installs a
PropertyChangeListener
on theAction
so that the component can change its properties to reflect changes in theAction
's properties.
The following table describes the properties used by Swing
components that support Actions
. In the table, button refers to any AbstractButton
subclass, which includes not only JButton
but also classes such as JMenuItem
. Unless otherwise stated, a null
property value in an Action
(or a Action
that is null
) results in the button's corresponding property being set to null
.
Component Property | Components | Action Key | Notes |
---|---|---|---|
enabled |
All | The isEnabled method |
|
toolTipText |
All |
SHORT_DESCRIPTION |
|
actionCommand |
All |
ACTION_COMMAND_KEY |
|
mnemonic |
All buttons |
MNEMONIC_KEY |
A null value or Action results in the button's mnemonic property being set to '\0' . |
text |
All buttons |
NAME |
If you do not want the text of the button to mirror that of the Action , set the property hideActionText to true . If hideActionText is true , setting the Action changes the text of the button to null and any changes to NAME are ignored. hideActionText is useful for tool bar buttons that typically only show an Icon . JToolBar.add(Action) sets the property to true if the Action has a non-null value for LARGE_ICON_KEY or SMALL_ICON . |
displayedMnemonicIndex |
All buttons |
DISPLAYED_MNEMONIC_INDEX_KEY |
If the value of DISPLAYED_MNEMONIC_INDEX_KEY is beyond the bounds of the text, it is ignored. When setAction is called, if the value from the Action is null , the displayed mnemonic index is not updated. In any subsequent changes to DISPLAYED_MNEMONIC_INDEX_KEY , null is treated as -1. |
icon |
All buttons except of JCheckBox , JToggleButton and JRadioButton . |
either LARGE_ICON_KEY or SMALL_ICON |
The JMenuItem subclasses only use SMALL_ICON . All other buttons will use LARGE_ICON_KEY ; if the value is null they use SMALL_ICON . |
accelerator |
All JMenuItem subclasses, with the exception of JMenu . |
ACCELERATOR_KEY |
|
selected |
JToggleButton , JCheckBox , JRadioButton , JCheckBoxMenuItem and JRadioButtonMenuItem |
SELECTED_KEY |
Components that honor this property only use the value if it is non-null . For example, if you set an Action that has a null value for SELECTED_KEY on a JToggleButton , the JToggleButton will not update it's selected state in any way. Similarly, any time the JToggleButton 's selected state changes it will only set the value back on the Action if the Action has a non-null value for SELECTED_KEY . Components that honor this property keep their selected state in sync with this property. When the same Action is used with multiple components, all the components keep their selected state in sync with this property. Mutually exclusive buttons, such as JToggleButton s in a ButtonGroup , force only one of the buttons to be selected. As such, do not use the same Action that defines a value for the SELECTED_KEY property with multiple mutually exclusive buttons. |
JPopupMenu
, JToolBar
and JMenu
all provide convenience methods for creating a component and setting the Action
on the corresponding component. Refer to each of these classes for more information.
Action
uses PropertyChangeListener
to inform listeners the Action
has changed. The beans specification indicates that a null
property name can be used to indicate multiple values have changed. By default Swing components that take an Action
do not handle such a change. To indicate that Swing should treat null
according to the beans specification set the system property swing.actions.reconfigureOnNull
to the String
value true
.
- Since:
- 1.2
- See Also:
AbstractAction
Field Summary
Modifier and Type | Field | Description |
---|---|---|
static String | ACCELERATOR_KEY | The key used for storing a |
static String | ACTION_COMMAND_KEY | The key used to determine the command |
static String | DEFAULT | Not currently used. |
static String | DISPLAYED_MNEMONIC_INDEX_KEY | The key used for storing an |
static String | LARGE_ICON_KEY | The key used for storing an |
static String | LONG_DESCRIPTION | The key used for storing a longer |
static String | MNEMONIC_KEY | The key used for storing an |
static String | NAME | The key used for storing the |
static String | SELECTED_KEY | The key used for storing a |
static String | SHORT_DESCRIPTION | The key used for storing a short |
static String | SMALL_ICON | The key used for storing a small |
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 | addPropertyChangeListener(PropertyChangeListener listener) | Adds a |
Object | getValue(String key) | Gets one of this object's properties using the associated key. |
boolean | isEnabled() | Returns the enabled state of the |
void | putValue(String key,
Object value) | Sets one of this object's properties using the associated key. |
void | removePropertyChangeListener(PropertyChangeListener listener) | Removes a |
void | setEnabled(boolean b) | Sets the enabled state of the |
Methods declared in interface java.awt.event.ActionListener
actionPerformed
Field Detail
DEFAULT
static final String DEFAULT
Not currently used.
- See Also:
- Constant Field Values
NAME
static final String NAME
The key used for storing the String
name for the action, used for a menu or button.
- See Also:
- Constant Field Values
SHORT_DESCRIPTION
static final String SHORT_DESCRIPTION
The key used for storing a short String
description for the action, used for tooltip text.
- See Also:
- Constant Field Values
LONG_DESCRIPTION
static final String LONG_DESCRIPTION
The key used for storing a longer String
description for the action, could be used for context-sensitive help.
- See Also:
- Constant Field Values
SMALL_ICON
static final String SMALL_ICON
The key used for storing a small Icon
, such as ImageIcon
. This is typically used with menus such as JMenuItem
.
If the same Action
is used with menus and buttons you'll typically specify both a SMALL_ICON
and a LARGE_ICON_KEY
. The menu will use the SMALL_ICON
and the button will use the LARGE_ICON_KEY
.
- See Also:
- Constant Field Values
ACTION_COMMAND_KEY
static final String ACTION_COMMAND_KEY
The key used to determine the command String
for the ActionEvent
that will be created when an Action
is going to be notified as the result of residing in a Keymap
associated with a JComponent
.
- See Also:
- Constant Field Values
ACCELERATOR_KEY
static final String ACCELERATOR_KEY
The key used for storing a KeyStroke
to be used as the accelerator for the action.
- Since:
- 1.3
- See Also:
- Constant Field Values
MNEMONIC_KEY
static final String MNEMONIC_KEY
The key used for storing an Integer
that corresponds to one of the KeyEvent
key codes. The value is commonly used to specify a mnemonic. For example: myAction.putValue(Action.MNEMONIC_KEY, KeyEvent.VK_A)
sets the mnemonic of myAction
to 'a', while myAction.putValue(Action.MNEMONIC_KEY, KeyEvent.getExtendedKeyCodeForChar('Ñ'))
sets the mnemonic of myAction
to Cyrillic letter "Ef".
- Since:
- 1.3
- See Also:
- Constant Field Values
SELECTED_KEY
static final String SELECTED_KEY
The key used for storing a Boolean
that corresponds to the selected state. This is typically used only for components that have a meaningful selection state. For example, JRadioButton
and JCheckBox
make use of this but instances of JMenu
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 an Action
is attached to a JCheckBox
the selected state of the JCheckBox
will be set from that of the Action
. If the user clicks on the JCheckBox
the selected state of the JCheckBox
and the Action
will 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
DISPLAYED_MNEMONIC_INDEX_KEY
static final String DISPLAYED_MNEMONIC_INDEX_KEY
The key used for storing an Integer
that corresponds to the index in the text (identified by the NAME
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 existing Actions
.
- Since:
- 1.6
- See Also:
-
AbstractButton.setDisplayedMnemonicIndex(int)
, Constant Field Values
LARGE_ICON_KEY
static final String LARGE_ICON_KEY
The key used for storing an Icon
. This is typically used by buttons, such as JButton
and JToggleButton
.
If the same Action
is used with menus and buttons you'll typically specify both a SMALL_ICON
and a LARGE_ICON_KEY
. The menu will use the SMALL_ICON
and the button the LARGE_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
Method Detail
getValue
Object getValue(String key)
Gets one of this object's properties using the associated key.
- Parameters:
-
key
- aString
containing the key - Returns:
- the
Object
value - See Also:
putValue(java.lang.String, java.lang.Object)
putValue
void putValue(String key, Object value)
Sets one of this object's properties using the associated key. If the value has changed, a PropertyChangeEvent
is sent to listeners.
- Parameters:
-
key
- aString
containing the key -
value
- anObject
value
setEnabled
void setEnabled(boolean b)
Sets the enabled state of the Action
. When enabled, any component associated with this object is active and able to fire this object's actionPerformed
method. If the value has changed, a PropertyChangeEvent
is sent to listeners.
- Parameters:
-
b
- true to enable thisAction
, false to disable it - See Also:
accept(java.lang.Object)
isEnabled
boolean isEnabled()
Returns the enabled state of the Action
. When enabled, any component associated with this object is active and able to fire this object's actionPerformed
method.
- Returns:
- true if this
Action
is enabled - See Also:
accept(java.lang.Object)
accept
default boolean accept(Object sender)
Determines whether the action should be performed with the specified sender object. The sender
can be null
. 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:
-
isEnabled()
,setEnabled(boolean)
addPropertyChangeListener
void addPropertyChangeListener(PropertyChangeListener listener)
Adds a PropertyChange
listener. Containers and attached components use these methods to register interest in this Action
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 a PropertyChange
listener.
- Parameters:
-
listener
- aPropertyChangeListener
object - See Also:
addPropertyChangeListener(java.beans.PropertyChangeListener)