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25 package javax.swing;
26
27 import java.awt.*;
28 import java.awt.event.*;
29 import java.beans.*;
30
31 /**
32 * The <code>Action</code> interface provides a useful extension to the
33 * <code>ActionListener</code>
34 * interface in cases where the same functionality may be accessed by
35 * several controls.
36 * <p>
37 * In addition to the <code>actionPerformed</code> method defined by the
38 * <code>ActionListener</code> interface, this interface allows the
39 * application to define, in a single place:
40 * <ul>
41 * <li>One or more text strings that describe the function. These strings
42 * can be used, for example, to display the flyover text for a button
43 * or to set the text in a menu item.
44 * <li>One or more icons that depict the function. These icons can be used
45 * for the images in a menu control, or for composite entries in a more
46 * sophisticated user interface.
47 * <li>The enabled/disabled state of the functionality. Instead of having
48 * to separately disable the menu item and the toolbar button, the
49 * application can disable the function that implements this interface.
50 * All components which are registered as listeners for the state change
51 * then know to disable event generation for that item and to modify the
52 * display accordingly.
53 * </ul>
54 * <p>
55 * This interface can be added to an existing class or used to create an
56 * adapter (typically, by subclassing <code>AbstractAction</code>).
57 * The <code>Action</code> object
58 * can then be added to multiple <code>Action</code>-aware containers
59 * and connected to <code>Action</code>-capable
60 * components. The GUI controls can then be activated or
61 * deactivated all at once by invoking the <code>Action</code> object's
62 * <code>setEnabled</code> method.
63 * <p>
64 * Note that <code>Action</code> implementations tend to be more expensive
65 * in terms of storage than a typical <code>ActionListener</code>,
66 * which does not offer the benefits of centralized control of
67 * functionality and broadcast of property changes. For this reason,
68 * you should take care to only use <code>Action</code>s where their benefits
69 * are desired, and use simple <code>ActionListener</code>s elsewhere.
70 * <br>
71 *
72 * <h3><a id="buttonActions"></a>Swing Components Supporting <code>Action</code></h3>
73 * <p>
74 * Many of Swing's components have an <code>Action</code> property. When
75 * an <code>Action</code> is set on a component, the following things
76 * happen:
77 * <ul>
78 * <li>The <code>Action</code> is added as an <code>ActionListener</code> to
79 * the component.
80 * <li>The component configures some of its properties to match the
81 * <code>Action</code>.
82 * <li>The component installs a <code>PropertyChangeListener</code> on the
83 * <code>Action</code> so that the component can change its properties
84 * to reflect changes in the <code>Action</code>'s properties.
85 * </ul>
86 * <p>
87 * The following table describes the properties used by
88 * <code>Swing</code> components that support <code>Actions</code>.
89 * In the table, <em>button</em> refers to any
90 * <code>AbstractButton</code> subclass, which includes not only
91 * <code>JButton</code> but also classes such as
92 * <code>JMenuItem</code>. Unless otherwise stated, a
93 * <code>null</code> property value in an <code>Action</code> (or a
94 * <code>Action</code> that is <code>null</code>) results in the
95 * button's corresponding property being set to <code>null</code>.
96 *
97 * <table class="striped">
98 * <caption>Supported Action properties</caption>
99 * <thead>
100 * <tr>
101 * <th scope="col">Component Property
102 * <th scope="col">Components
103 * <th scope="col">Action Key
104 * <th scope="col">Notes
105 * </thead>
106 * <tbody>
107 * <tr>
108 * <th scope="row"><b>{@code enabled}</b>
109 * <td>All
110 * <td>The {@code isEnabled} method
111 * <td>
112 * <tr>
113 * <th scope="row"><b>{@code toolTipText}</b>
114 * <td>All
115 * <td>{@code SHORT_DESCRIPTION}
116 * <td>
117 * <tr>
118 * <th scope="row"><b>{@code actionCommand}</b>
119 * <td>All
120 * <td>{@code ACTION_COMMAND_KEY}
121 * <td>
122 * <tr>
123 * <th scope="row"><b>{@code mnemonic}</b>
124 * <td>All buttons
125 * <td>{@code MNEMONIC_KEY}
126 * <td>A {@code null} value or {@code Action} results in the button's
127 * {@code mnemonic} property being set to {@code '\0'}.
128 * <tr>
129 * <th scope="row"><b>{@code text}</b>
130 * <td>All buttons
131 * <td>{@code NAME}
132 * <td>If you do not want the text of the button to mirror that of the
133 * {@code Action}, set the property {@code hideActionText} to {@code true}.
134 * If {@code hideActionText} is {@code true}, setting the {@code Action}
135 * changes the text of the button to {@code null} and any changes to
136 * {@code NAME} are ignored. {@code hideActionText} is useful for tool bar
137 * buttons that typically only show an {@code Icon}.
138 * {@code JToolBar.add(Action)} sets the property to {@code true} if the
139 * {@code Action} has a non-{@code null} value for {@code LARGE_ICON_KEY} or
140 * {@code SMALL_ICON}.
141 * <tr>
142 * <th scope="row"><b>{@code displayedMnemonicIndex}</b>
143 * <td>All buttons
144 * <td>{@code DISPLAYED_MNEMONIC_INDEX_KEY}
145 * <td>If the value of {@code DISPLAYED_MNEMONIC_INDEX_KEY} is beyond the
146 * bounds of the text, it is ignored. When {@code setAction} is called, if
147 * the value from the {@code Action} is {@code null}, the displayed mnemonic
148 * index is not updated. In any subsequent changes to
149 * {@code DISPLAYED_MNEMONIC_INDEX_KEY}, {@code null} is treated as -1.
150 * <tr>
151 * <th scope="row"><b>{@code icon}</b>
152 * <td>All buttons except of {@code JCheckBox}, {@code JToggleButton} and
153 * {@code JRadioButton}.
154 * <td>either {@code LARGE_ICON_KEY} or {@code SMALL_ICON}
155 * <td>The {@code JMenuItem} subclasses only use {@code SMALL_ICON}. All
156 * other buttons will use {@code LARGE_ICON_KEY}; if the value is
157 * {@code null} they use {@code SMALL_ICON}.
158 * <tr>
159 * <th scope="row"><b>{@code accelerator}</b>
160 * <td>All {@code JMenuItem} subclasses, with the exception of {@code JMenu}.
161 * <td>{@code ACCELERATOR_KEY}
162 * <td>
163 * <tr>
164 * <th scope="row"><b>{@code selected}</b>
165 * <td>{@code JToggleButton}, {@code JCheckBox}, {@code JRadioButton},
166 * {@code JCheckBoxMenuItem} and {@code JRadioButtonMenuItem}
167 * <td>{@code SELECTED_KEY}
168 * <td>Components that honor this property only use the value if it is
169 * {@code non-null}. For example, if you set an {@code Action} that has a
170 * {@code null} value for {@code SELECTED_KEY} on a {@code JToggleButton},
171 * the {@code JToggleButton} will not update it's selected state in any way.
172 * Similarly, any time the {@code JToggleButton}'s selected state changes it
173 * will only set the value back on the {@code Action} if the {@code Action}
174 * has a {@code non-null} value for {@code SELECTED_KEY}.
175 * <br>
176 * Components that honor this property keep their selected state in sync with
177 * this property. When the same {@code Action} is used with multiple
178 * components, all the components keep their selected state in sync with this
179 * property. Mutually exclusive buttons, such as {@code JToggleButton}s in a
180 * {@code ButtonGroup}, force only one of the buttons to be selected. As
181 * such, do not use the same {@code Action} that defines a value for the
182 * {@code SELECTED_KEY} property with multiple mutually exclusive buttons.
183 * </tbody>
184 * </table>
185 * <p>
186 * <code>JPopupMenu</code>, <code>JToolBar</code> and <code>JMenu</code>
187 * all provide convenience methods for creating a component and setting the
188 * <code>Action</code> on the corresponding component. Refer to each of
189 * these classes for more information.
190 * <p>
191 * <code>Action</code> uses <code>PropertyChangeListener</code> to
192 * inform listeners the <code>Action</code> has changed. The beans
193 * specification indicates that a <code>null</code> property name can
194 * be used to indicate multiple values have changed. By default Swing
195 * components that take an <code>Action</code> do not handle such a
196 * change. To indicate that Swing should treat <code>null</code>
197 * according to the beans specification set the system property
198 * <code>swing.actions.reconfigureOnNull</code> to the <code>String</code>
199 * value <code>true</code>.
200 *
201 * @author Georges Saab
202 * @see AbstractAction
203 * @since 1.2
204 */
205 public interface Action extends ActionListener {
206 /**
207 * Useful constants that can be used as the storage-retrieval key
208 * when setting or getting one of this object's properties (text
209 * or icon).
210 */
211 /**
212 * Not currently used.
213 */
214 public static final String DEFAULT = "Default";
215 /**
216 * The key used for storing the <code>String</code> name
217 * for the action, used for a menu or button.
218 */
219 public static final String NAME = "Name";
220 /**
221 * The key used for storing a short <code>String</code>
222 * description for the action, used for tooltip text.
223 */
224 public static final String SHORT_DESCRIPTION = "ShortDescription";
225 /**
226 * The key used for storing a longer <code>String</code>
227 * description for the action, could be used for context-sensitive help.
228 */
229 public static final String LONG_DESCRIPTION = "LongDescription";
230 /**
231 * The key used for storing a small <code>Icon</code>, such
232 * as <code>ImageIcon</code>. This is typically used with
233 * menus such as <code>JMenuItem</code>.
234 * <p>
235 * If the same <code>Action</code> is used with menus and buttons you'll
236 * typically specify both a <code>SMALL_ICON</code> and a
237 * <code>LARGE_ICON_KEY</code>. The menu will use the
238 * <code>SMALL_ICON</code> and the button will use the
239 * <code>LARGE_ICON_KEY</code>.
240 */
241 public static final String SMALL_ICON = "SmallIcon";
242
243 /**
244 * The key used to determine the command <code>String</code> for the
245 * <code>ActionEvent</code> that will be created when an
246 * <code>Action</code> is going to be notified as the result of
247 * residing in a <code>Keymap</code> associated with a
248 * <code>JComponent</code>.
249 */
250 public static final String ACTION_COMMAND_KEY = "ActionCommandKey";
251
252 /**
253 * The key used for storing a <code>KeyStroke</code> to be used as the
254 * accelerator for the action.
255 *
256 * @since 1.3
257 */
258 public static final String ACCELERATOR_KEY="AcceleratorKey";
259
260 /**
261 * The key used for storing an <code>Integer</code> that corresponds to
262 * one of the <code>KeyEvent</code> key codes. The value is
263 * commonly used to specify a mnemonic. For example:
264 * <code>myAction.putValue(Action.MNEMONIC_KEY, KeyEvent.VK_A)</code>
265 * sets the mnemonic of <code>myAction</code> to 'a', while
266 * <code>myAction.putValue(Action.MNEMONIC_KEY, KeyEvent.getExtendedKeyCodeForChar('\u0444'))</code>
267 * sets the mnemonic of <code>myAction</code> to Cyrillic letter "Ef".
268 *
269 * @since 1.3
270 */
271 public static final String MNEMONIC_KEY="MnemonicKey";
272
273 /**
274 * The key used for storing a <code>Boolean</code> that corresponds
275 * to the selected state. This is typically used only for components
276 * that have a meaningful selection state. For example,
277 * <code>JRadioButton</code> and <code>JCheckBox</code> make use of
278 * this but instances of <code>JMenu</code> don't.
279 * <p>
280 * This property differs from the others in that it is both read
281 * by the component and set by the component. For example,
282 * if an <code>Action</code> is attached to a <code>JCheckBox</code>
283 * the selected state of the <code>JCheckBox</code> will be set from
284 * that of the <code>Action</code>. If the user clicks on the
285 * <code>JCheckBox</code> the selected state of the <code>JCheckBox</code>
286 * <b>and</b> the <code>Action</code> will <b>both</b> be updated.
287 * <p>
288 * Note: the value of this field is prefixed with 'Swing' to
289 * avoid possible collisions with existing <code>Actions</code>.
290 *
291 * @since 1.6
292 */
293 public static final String SELECTED_KEY = "SwingSelectedKey";
294
295 /**
296 * The key used for storing an <code>Integer</code> that corresponds
297 * to the index in the text (identified by the <code>NAME</code>
298 * property) that the decoration for a mnemonic should be rendered at. If
299 * the value of this property is greater than or equal to the length of
300 * the text, it will treated as -1.
301 * <p>
302 * Note: the value of this field is prefixed with 'Swing' to
303 * avoid possible collisions with existing <code>Actions</code>.
304 *
305 * @see AbstractButton#setDisplayedMnemonicIndex
306 * @since 1.6
307 */
308 public static final String DISPLAYED_MNEMONIC_INDEX_KEY =
309 "SwingDisplayedMnemonicIndexKey";
310
311 /**
312 * The key used for storing an <code>Icon</code>. This is typically
313 * used by buttons, such as <code>JButton</code> and
314 * <code>JToggleButton</code>.
315 * <p>
316 * If the same <code>Action</code> is used with menus and buttons you'll
317 * typically specify both a <code>SMALL_ICON</code> and a
318 * <code>LARGE_ICON_KEY</code>. The menu will use the
319 * <code>SMALL_ICON</code> and the button the <code>LARGE_ICON_KEY</code>.
320 * <p>
321 * Note: the value of this field is prefixed with 'Swing' to
322 * avoid possible collisions with existing <code>Actions</code>.
323 *
324 * @since 1.6
325 */
326 public static final String LARGE_ICON_KEY = "SwingLargeIconKey";
327
328 /**
329 * Gets one of this object's properties
330 * using the associated key.
331 *
332 * @param key a {@code String} containing the key
333 * @return the {@code Object} value
334 * @see #putValue
335 */
336 public Object getValue(String key);
337 /**
338 * Sets one of this object's properties
339 * using the associated key. If the value has
340 * changed, a <code>PropertyChangeEvent</code> is sent
341 * to listeners.
342 *
343 * @param key a <code>String</code> containing the key
344 * @param value an <code>Object</code> value
345 */
346 public void putValue(String key, Object value);
347
348 /**
349 * Sets the enabled state of the {@code Action}. When enabled,
350 * any component associated with this object is active and
351 * able to fire this object's {@code actionPerformed} method.
352 * If the value has changed, a {@code PropertyChangeEvent} is sent
353 * to listeners.
354 *
355 * @param b true to enable this {@code Action}, false to disable it
356 * @see #accept
357 */
358 public void setEnabled(boolean b);
359 /**
360 * Returns the enabled state of the {@code Action}. When enabled,
361 * any component associated with this object is active and
362 * able to fire this object's {@code actionPerformed} method.
363 *
364 * @return true if this {@code Action} is enabled
365 * @see #accept
366 */
367 public boolean isEnabled();
368
369 /**
370 * Determines whether the action should be performed with the specified
371 * sender object. The {@code sender} can be {@code null}.
372 * The method must return false if the action is disabled.
373 * <p>
374 * @param sender the object to check, can be null
375 * @return {@code true} if the action should be performed with the sender
376 * object, must be false if the action is disabled.
377 * @see #isEnabled
378 * @see #setEnabled
379 */
380 default boolean accept(Object sender) {
381 return isEnabled();
382 }
383
384 /**
385 * Adds a <code>PropertyChange</code> listener. Containers and attached
386 * components use these methods to register interest in this
387 * <code>Action</code> object. When its enabled state or other property
388 * changes, the registered listeners are informed of the change.
389 *
390 * @param listener a <code>PropertyChangeListener</code> object
391 */
392 public void addPropertyChangeListener(PropertyChangeListener listener);
393 /**
394 * Removes a <code>PropertyChange</code> listener.
395 *
396 * @param listener a <code>PropertyChangeListener</code> object
397 * @see #addPropertyChangeListener
398 */
399 public void removePropertyChangeListener(PropertyChangeListener listener);
400
401 }