javax.swing.Action — clojure-interop/javax.swing 1.0.5

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 JToggleButtons 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.

add-property-change-listener clj

(add-property-change-listener this 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.

listener - a PropertyChangeListener object - java.beans.PropertyChangeListener

enabled? clj

(enabled? this)

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 - boolean

get-value clj

(get-value this key)

Gets one of this object's properties using the associated key.

key - java.lang.String

returns: java.lang.Object

put-value clj

(put-value this key value)

Sets one of this object's properties using the associated key. If the value has changed, a PropertyChangeEvent is sent to listeners.

key - a String containing the key - java.lang.String value - an Object value - java.lang.Object

remove-property-change-listener clj

(remove-property-change-listener this listener)

Removes a PropertyChange listener.

listener - a PropertyChangeListener object - java.beans.PropertyChangeListener

set-enabled clj

(set-enabled this 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.

b - true to enable this Action, false to disable it - boolean