Java example source code file (Action.java)

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The Action.java Java example source code

/*
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 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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 * under the terms of the GNU General Public License version 2 only, as
 * published by the Free Software Foundation.  Oracle designates this
 * particular file as subject to the "Classpath" exception as provided
 * by Oracle in the LICENSE file that accompanied this code.
 *
 * This code is distributed in the hope that it will be useful, but WITHOUT
 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
 * version 2 for more details (a copy is included in the LICENSE file that
 * accompanied this code).
 *
 * You should have received a copy of the GNU General Public License version
 * 2 along with this work; if not, write to the Free Software Foundation,
 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
 *
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package javax.swing;

import java.awt.*;
import java.awt.event.*;
import java.beans.*;

/**
 * The <code>Action interface provides a useful extension to the
 * <code>ActionListener
 * interface in cases where the same functionality may be accessed by
 * several controls.
 * <p>
 * In addition to the <code>actionPerformed method defined by the
 * <code>ActionListener interface, this interface allows the
 * application to define, in a single place:
 * <ul>
 * <li>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.
 * <li>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.
 * <li>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.
 * </ul>
 * <p>
 * This interface can be added to an existing class or used to create an
 * adapter (typically, by subclassing <code>AbstractAction).
 * The <code>Action object
 * can then be added to multiple <code>Action-aware containers
 * and connected to <code>Action-capable
 * components. The GUI controls can then be activated or
 * deactivated all at once by invoking the <code>Action object's
 * <code>setEnabled method.
 * <p>
 * Note that <code>Action implementations tend to be more expensive
 * in terms of storage than a typical <code>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 <code>Actions where their benefits
 * are desired, and use simple <code>ActionListeners elsewhere.
 * <br>
 *
 * <h3>Swing Components Supporting Action
 * <p>
 * Many of Swing's components have an <code>Action property.  When
 * an <code>Action is set on a component, the following things
 * happen:
 * <ul>
 * <li>The Action is added as an ActionListener to
 *     the component.
 * <li>The component configures some of its properties to match the
 *      <code>Action.
 * <li>The component installs a PropertyChangeListener on the
 *     <code>Action so that the component can change its properties
 *     to reflect changes in the <code>Action's properties.
 * </ul>
 * <p>
 * The following table describes the properties used by
 * <code>Swing components that support Actions.
 * In the table, <em>button refers to any
 * <code>AbstractButton subclass, which includes not only
 * <code>JButton but also classes such as
 * <code>JMenuItem. Unless otherwise stated, a
 * <code>null property value in an Action (or a
 * <code>Action that is null) results in the
 * button's corresponding property being set to <code>null.
 *
 * <table border="1" cellpadding="1" cellspacing="0"
 *         summary="Supported Action properties">
 *  <tr valign="top"  align="left">
 *    <th style="background-color:#CCCCFF" align="left">Component Property
 *    <th style="background-color:#CCCCFF" align="left">Components
 *    <th style="background-color:#CCCCFF" align="left">Action Key
 *    <th style="background-color:#CCCCFF" align="left">Notes
 *  <tr valign="top"  align="left">
 *      <td>enabled
 *      <td>All
 *      <td>The isEnabled method
 *      <td> 
 *  <tr valign="top"  align="left">
 *      <td>toolTipText
 *      <td>All
 *      <td>SHORT_DESCRIPTION
 *      <td> 
 *  <tr valign="top"  align="left">
 *      <td>actionCommand
 *      <td>All
 *      <td>ACTION_COMMAND_KEY
 *      <td> 
 *  <tr valign="top"  align="left">
 *      <td>mnemonic
 *      <td>All buttons
 *      <td>MNEMONIC_KEY
 *      <td>A null value or Action results in the
 *          button's <code>mnemonic property being set to
 *          <code>'\0'.
 *  <tr valign="top"  align="left">
 *      <td>text
 *      <td>All buttons
 *      <td>NAME
 *      <td>If you do not want the text of the button to mirror that
 *          of the <code>Action, set the property
 *          <code>hideActionText to true.  If
 *          <code>hideActionText is true, setting the
 *          <code>Action changes the text of the button to
 *          <code>null and any changes to NAME
 *          are ignored.  <code>hideActionText is useful for
 *          tool bar buttons that typically only show an <code>Icon.
 *          <code>JToolBar.add(Action) sets the property to
 *          <code>true if the Action has a
 *          non-<code>null value for LARGE_ICON_KEY or
 *          <code>SMALL_ICON.
 *  <tr valign="top"  align="left">
 *      <td>displayedMnemonicIndex
 *      <td>All buttons
 *      <td>DISPLAYED_MNEMONIC_INDEX_KEY
 *      <td>If the value of DISPLAYED_MNEMONIC_INDEX_KEY is
 *          beyond the bounds of the text, it is ignored.  When
 *          <code>setAction is called, if the value from the
 *          <code>Action is null, the displayed
 *          mnemonic index is not updated.  In any subsequent changes to
 *          <code>DISPLAYED_MNEMONIC_INDEX_KEY, null
 *          is treated as -1.
 *  <tr valign="top"  align="left">
 *      <td>icon
 *      <td>All buttons except of JCheckBox,
 *      <code>JToggleButton and JRadioButton.
 *      <td>either LARGE_ICON_KEY or
 *          <code>SMALL_ICON
 *     <td>The JMenuItem subclasses only use
 *         <code>SMALL_ICON.  All other buttons will use
 *         <code>LARGE_ICON_KEY; if the value is null they
 *         use <code>SMALL_ICON.
 *  <tr valign="top"  align="left">
 *      <td>accelerator
 *      <td>All JMenuItem subclasses, with the exception of
 *          <code>JMenu.
 *      <td>ACCELERATOR_KEY
 *      <td> 
 *  <tr valign="top"  align="left">
 *      <td>selected
 *      <td>JToggleButton, JCheckBox,
 *          <code>JRadioButton, JCheckBoxMenuItem and
 *          <code>JRadioButtonMenuItem
 *      <td>SELECTED_KEY
 *      <td>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}.
 *          <br>
 *          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.
 * </table>
 * <p>
 * <code>JPopupMenu, JToolBar and JMenu
 * all provide convenience methods for creating a component and setting the
 * <code>Action on the corresponding component.  Refer to each of
 * these classes for more information.
 * <p>
 * <code>Action uses PropertyChangeListener to
 * inform listeners the <code>Action has changed.  The beans
 * specification indicates that a <code>null property name can
 * be used to indicate multiple values have changed.  By default Swing
 * components that take an <code>Action do not handle such a
 * change.  To indicate that Swing should treat <code>null
 * according to the beans specification set the system property
 * <code>swing.actions.reconfigureOnNull to the String
 * value <code>true.
 *
 * @author Georges Saab
 * @see AbstractAction
 */
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 <code>String name
     * for the action, used for a menu or button.
     */
    public static final String NAME = "Name";
    /**
     * The key used for storing a short <code>String
     * description for the action, used for tooltip text.
     */
    public static final String SHORT_DESCRIPTION = "ShortDescription";
    /**
     * The key used for storing a longer <code>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 <code>Icon, such
     * as <code>ImageIcon.  This is typically used with
     * menus such as <code>JMenuItem.
     * <p>
     * If the same <code>Action is used with menus and buttons you'll
     * typically specify both a <code>SMALL_ICON and a
     * <code>LARGE_ICON_KEY.  The menu will use the
     * <code>SMALL_ICON and the button will use the
     * <code>LARGE_ICON_KEY.
     */
    public static final String SMALL_ICON = "SmallIcon";

    /**
     * The key used to determine the command <code>String for the
     * <code>ActionEvent that will be created when an
     * <code>Action is going to be notified as the result of
     * residing in a <code>Keymap associated with a
     * <code>JComponent.
     */
    public static final String ACTION_COMMAND_KEY = "ActionCommandKey";

    /**
     * The key used for storing a <code>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 <code>Integer that corresponds to
     * one of the <code>KeyEvent key codes.  The value is
     * commonly used to specify a mnemonic.  For example:
     * <code>myAction.putValue(Action.MNEMONIC_KEY, KeyEvent.VK_A)
     * sets the mnemonic of <code>myAction to 'a', while
     * <code>myAction.putValue(Action.MNEMONIC_KEY, KeyEvent.getExtendedKeyCodeForChar('\u0444'))
     * sets the mnemonic of <code>myAction to Cyrillic letter "Ef".
     *
     * @since 1.3
     */
    public static final String MNEMONIC_KEY="MnemonicKey";

    /**
     * The key used for storing a <code>Boolean that corresponds
     * to the selected state.  This is typically used only for components
     * that have a meaningful selection state.  For example,
     * <code>JRadioButton and JCheckBox make use of
     * this but instances of <code>JMenu don't.
     * <p>
     * This property differs from the others in that it is both read
     * by the component and set by the component.  For example,
     * if an <code>Action is attached to a JCheckBox
     * the selected state of the <code>JCheckBox will be set from
     * that of the <code>Action.  If the user clicks on the
     * <code>JCheckBox the selected state of the JCheckBox
     * <b>and the Action will both be updated.
     * <p>
     * Note: the value of this field is prefixed with 'Swing' to
     * avoid possible collisions with existing <code>Actions.
     *
     * @since 1.6
     */
    public static final String SELECTED_KEY = "SwingSelectedKey";

    /**
     * The key used for storing an <code>Integer that corresponds
     * to the index in the text (identified by the <code>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.
     * <p>
     * Note: the value of this field is prefixed with 'Swing' to
     * avoid possible collisions with existing <code>Actions.
     *
     * @see AbstractButton#setDisplayedMnemonicIndex
     * @since 1.6
     */
    public static final String DISPLAYED_MNEMONIC_INDEX_KEY =
                                 "SwingDisplayedMnemonicIndexKey";

    /**
     * The key used for storing an <code>Icon.  This is typically
     * used by buttons, such as <code>JButton and
     * <code>JToggleButton.
     * <p>
     * If the same <code>Action is used with menus and buttons you'll
     * typically specify both a <code>SMALL_ICON and a
     * <code>LARGE_ICON_KEY.  The menu will use the
     * <code>SMALL_ICON and the button the LARGE_ICON_KEY.
     * <p>
     * Note: the value of this field is prefixed with 'Swing' to
     * avoid possible collisions with existing <code>Actions.
     *
     * @since 1.6
     */
    public static final String LARGE_ICON_KEY = "SwingLargeIconKey";

    /**
     * Gets one of this object's properties
     * using the associated key.
     * @see #putValue
     */
    public Object getValue(String key);
    /**
     * Sets one of this object's properties
     * using the associated key. If the value has
     * changed, a <code>PropertyChangeEvent is sent
     * to listeners.
     *
     * @param key    a <code>String containing the key
     * @param value  an <code>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
     */
    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
     */
    public boolean isEnabled();

    /**
     * Adds a <code>PropertyChange listener. Containers and attached
     * components use these methods to register interest in this
     * <code>Action object. When its enabled state or other property
     * changes, the registered listeners are informed of the change.
     *
     * @param listener  a <code>PropertyChangeListener object
     */
    public void addPropertyChangeListener(PropertyChangeListener listener);
    /**
     * Removes a <code>PropertyChange listener.
     *
     * @param listener  a <code>PropertyChangeListener object
     * @see #addPropertyChangeListener
     */
    public void removePropertyChangeListener(PropertyChangeListener listener);

}