Action (Java Platform SE 8 )

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 Actions where their benefits are desired, and use simple ActionListeners 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 an ActionListener to the component.
The component configures some of its properties to match the Action.
The component installs a PropertyChangeListener on the Action so that the component can change its properties to reflect changes in the Action'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.

See Also:: AbstractAction

Field Summary

Fields
Modifier and Type	Field and Description
`static String`	`ACCELERATOR_KEY` The key used for storing a `KeyStroke` to be used as the accelerator for the action.
`static 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`.
`static String`	`DEFAULT` Not currently used.
`static 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.
`static String`	`LARGE_ICON_KEY` The key used for storing an `Icon`.
`static String`	`LONG_DESCRIPTION` The key used for storing a longer `String` description for the action, could be used for context-sensitive help.
`static String`	`MNEMONIC_KEY` The key used for storing an `Integer` that corresponds to one of the `KeyEvent` key codes.
`static String`	`NAME` The key used for storing the `String` name for the action, used for a menu or button.
`static String`	`SELECTED_KEY` The key used for storing a `Boolean` that corresponds to the selected state.
`static String`	`SHORT_DESCRIPTION` The key used for storing a short `String` description for the action, used for tooltip text.
`static String`	`SMALL_ICON` The key used for storing a small `Icon`, such as `ImageIcon`.

Method Summary

All Methods Instance Methods Abstract Methods
Modifier and Type	Method and Description
`void`	`addPropertyChangeListener(PropertyChangeListener listener)` Adds a `PropertyChange` listener.
`Object`	`getValue(String key)` Gets one of this object's properties using the associated key.
`boolean`	`isEnabled()` Returns the enabled state of the `Action`.
`void`	`putValue(String key, Object value)` Sets one of this object's properties using the associated key.
`void`	`removePropertyChangeListener(PropertyChangeListener listener)` Removes a `PropertyChange` listener.
`void`	`setEnabled(boolean b)` Sets the enabled state of the `Action`.

Methods inherited from 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('?')) 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.
    
    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 - a String containing the key
    
    value - an Object 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 this Action, false to disable it
  - 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
  - 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 - a PropertyChangeListener object
  - removePropertyChangeListener
```
void removePropertyChangeListener(PropertyChangeListener listener)
```
    Removes a PropertyChange listener.
    
    Parameters:
    
    listener - a PropertyChangeListener object
    
    See Also:
    
    addPropertyChangeListener(java.beans.PropertyChangeListener)

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Interface Action

Swing Components Supporting Action

Field Summary

Method Summary

Methods inherited from interface java.awt.event.ActionListener

Field Detail

DEFAULT

NAME

SHORT_DESCRIPTION

LONG_DESCRIPTION

SMALL_ICON

ACTION_COMMAND_KEY

ACCELERATOR_KEY

MNEMONIC_KEY

SELECTED_KEY

DISPLAYED_MNEMONIC_INDEX_KEY

LARGE_ICON_KEY

Method Detail

getValue

putValue

setEnabled

isEnabled

addPropertyChangeListener

removePropertyChangeListener

Swing Components Supporting `Action`