Action (Java Platform SE 6) (original) (raw)

javax.swing

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 theActionListener 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'ssetEnabled 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 theAction.
• The component installs a PropertyChangeListener on theAction so that the component can change its properties to reflect changes in the Action's properties.

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

JPopupMenu, JToolBar and JMenu 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 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 propertyswing.actions.reconfigureOnNull to the String value true.

See Also:

AbstractAction

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 aLARGE_ICON_KEY. The menu will use theSMALL_ICON and the button will use theLARGE_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 theActionEvent that will be created when anAction is going to be notified as the result of residing in a Keymap associated with aJComponent.

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'.

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 theJCheckBox 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 aLARGE_ICON_KEY. The menu will use theSMALL_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

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)](../../javax/swing/Action.html#putValue%28java.lang.String, java.lang.Object%29)

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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