charvax.swing

Interface Action

All Superinterfaces:
ActionListener, EventListener
Known Implementing Classes:
AbstractAction

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:

Certain containers, including menus and tool bars, know how to add an Action object. When an Action object is added to such a container, the container:
  1. Creates a component that is appropriate for that container (a tool bar creates a button component, for example).
  2. Gets the appropriate property(s) from the Action object to customize the component (for example, the icon image and flyover text).
  3. Checks the initial state of the Action object to determine if it is enabled or disabled, and renders the component in the appropriate fashion.
  4. Registers a listener with the Action object so that is notified of state changes. When the Action object changes from enabled to disabled, or back, the container makes the appropriate revisions to the event-generation mechanisms and renders the component accordingly.
For example, both a menu item and a toolbar button could access a Cut action object. The text associated with the object is specified as "Cut", and an image depicting a pair of scissors is specified as its icon. The Cut action-object can then be added to a menu and to a tool bar. Each container does the appropriate things with the object, and invokes its actionPerformed method when the component associated with it is activated. The application can then disable or enable the application object without worrying about what user-interface components are connected to it.

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.

Version:
1.30 12/19/03
Author:
Georges Saab
See Also:
AbstractAction

Field Summary

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
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 a KeyEvent to be used as the mnemonic for the action.
static String
NAME
The key used for storing the String name for the action, used for a menu or button.
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, for the action, used for toolbar buttons.

Method Summary

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 charva.awt.event.ActionListener

actionPerformed

Field Details

ACCELERATOR_KEY

public static final String ACCELERATOR_KEY
The key used for storing a KeyStroke to be used as the accelerator for the action.
Since:
1.3

ACTION_COMMAND_KEY

public 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.

DEFAULT

public static final String DEFAULT
Not currently used.

LONG_DESCRIPTION

public static final String LONG_DESCRIPTION
The key used for storing a longer String description for the action, could be used for context-sensitive help.

MNEMONIC_KEY

public static final String MNEMONIC_KEY
The key used for storing a KeyEvent to be used as the mnemonic for the action.
Since:
1.3

NAME

public static final String NAME
The key used for storing the String name for the action, used for a menu or button.

SHORT_DESCRIPTION

public static final String SHORT_DESCRIPTION
The key used for storing a short String description for the action, used for tooltip text.

SMALL_ICON

public static final String SMALL_ICON
The key used for storing a small Icon, such as ImageIcon, for the action, used for toolbar buttons.

Method Details

addPropertyChangeListener

public 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

getValue

public Object getValue(String key)
Gets one of this object's properties using the associated key.

isEnabled

public 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

putValue

public 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

removePropertyChangeListener

public void removePropertyChangeListener(PropertyChangeListener listener)
Removes a PropertyChange listener.
Parameters:
listener - a PropertyChangeListener object

setEnabled

public 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