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:
*
* 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.
*
*
*
Action
* Many of Swing's components have an Action property. When
* an Action is set on a component, the following things
* happen:
*
Action is added as an ActionListener to
* the component.
* Action.
* 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 {@code non-null}. For example, if
* you set an {@code Action} that has a {@code null}
* value for {@code SELECTED_KEY} on a {@code JToggleButton}, the
* {@code JToggleButton} will not update it's selected state in
* any way. Similarly, any time the {@code JToggleButton}'s
* selected state changes it will only set the value back on
* the {@code Action} if the {@code Action} has a {@code non-null}
* value for {@code SELECTED_KEY}.
* * Components that honor this property keep their selected state * in sync with this property. When the same {@code Action} is used * with multiple components, all the components keep their selected * state in sync with this property. Mutually exclusive * buttons, such as {@code JToggleButton}s in a {@code ButtonGroup}, * force only one of the buttons to be selected. As such, do not * use the same {@code Action} that defines a value for the * {@code 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.
*
* @author Georges Saab
* @see AbstractAction
* @since 1.2
*/
public interface Action extends ActionListener {
/**
* Useful constants that can be used as the storage-retrieval key
* when setting or getting one of this object's properties (text
* or icon).
*/
/**
* Not currently used.
*/
public static final String DEFAULT = "Default";
/**
* The key used for storing the String name
* for the action, used for a menu or button.
*/
public static final String NAME = "Name";
/**
* The key used for storing a short String
* description for the action, used for tooltip text.
*/
public static final String SHORT_DESCRIPTION = "ShortDescription";
/**
* The key used for storing a longer String
* description for the action, could be used for context-sensitive help.
*/
public static final String LONG_DESCRIPTION = "LongDescription";
/**
* 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.
*/
public static final String SMALL_ICON = "SmallIcon";
/**
* 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.
*/
public static final String ACTION_COMMAND_KEY = "ActionCommandKey";
/**
* The key used for storing a KeyStroke to be used as the
* accelerator for the action.
*
* @since 1.3
*/
public static final String ACCELERATOR_KEY="AcceleratorKey";
/**
* 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('\u0444'))
* sets the mnemonic of myAction to Cyrillic letter "Ef".
*
* @since 1.3
*/
public static final String MNEMONIC_KEY="MnemonicKey";
/**
* 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
*/
public static final String SELECTED_KEY = "SwingSelectedKey";
/**
* 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.
*
* @see AbstractButton#setDisplayedMnemonicIndex
* @since 1.6
*/
public static final String DISPLAYED_MNEMONIC_INDEX_KEY =
"SwingDisplayedMnemonicIndexKey";
/**
* 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
*/
public static final String LARGE_ICON_KEY = "SwingLargeIconKey";
/**
* Gets one of this object's properties
* using the associated key.
*
* @param key a {@code String} containing the key
* @return the {@code Object} value
* @see #putValue
*/
public Object getValue(String key);
/**
* Sets one of this object's properties
* using the associated key. If the value has
* changed, a PropertyChangeEvent is sent
* to listeners.
*
* @param key a String containing the key
* @param value an Object value
*/
public void putValue(String key, Object value);
/**
* Sets the enabled state of the {@code Action}. When enabled,
* any component associated with this object is active and
* able to fire this object's {@code actionPerformed} method.
* If the value has changed, a {@code PropertyChangeEvent} is sent
* to listeners.
*
* @param b true to enable this {@code Action}, false to disable it
* @see #accept
*/
public void setEnabled(boolean b);
/**
* Returns the enabled state of the {@code Action}. When enabled,
* any component associated with this object is active and
* able to fire this object's {@code actionPerformed} method.
*
* @return true if this {@code Action} is enabled
* @see #accept
*/
public boolean isEnabled();
/**
* Determines whether the action should be performed with the specified
* sender object. The {@code sender} can be {@code null}.
* The method must return false if the action is disabled.
*
* @param sender the object to check, can be null
* @return {@code true} if the action should be performed with the sender
* object, must be false if the action is disabled.
* @see #isEnabled
* @see #setEnabled
*/
default boolean accept(Object sender) {
return isEnabled();
}
/**
* 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.
*
* @param listener a PropertyChangeListener object
*/
public void addPropertyChangeListener(PropertyChangeListener listener);
/**
* Removes a PropertyChange listener.
*
* @param listener a PropertyChangeListener object
* @see #addPropertyChangeListener
*/
public void removePropertyChangeListener(PropertyChangeListener listener);
}