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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 style="display:none">Supported Action properties</caption>
99 * <thead>
100 * <tr>
101 * <th>Component Property
102 * <th>Components
103 * <th>Action Key
104 * <th>Notes
105 * </thead>
106 * <tbody>
107 * <tr valign="top" style="text-align:left">
108 * <td><b><code>enabled</code></b>
109 * <td>All
110 * <td>The <code>isEnabled</code> method
111 * <td>
112 * <tr valign="top" style="text-align:left">
113 * <td><b><code>toolTipText</code></b>
114 * <td>All
115 * <td><code>SHORT_DESCRIPTION</code>
116 * <td>
117 * <tr valign="top" style="text-align:left">
118 * <td><b><code>actionCommand</code></b>
119 * <td>All
120 * <td><code>ACTION_COMMAND_KEY</code>
121 * <td>
122 * <tr valign="top" style="text-align:left">
123 * <td><b><code>mnemonic</code></b>
124 * <td>All buttons
125 * <td><code>MNEMONIC_KEY</code>
126 * <td>A <code>null</code> value or <code>Action</code> results in the
127 * button's <code>mnemonic</code> property being set to
128 * <code>'\0'</code>.
129 * <tr valign="top" style="text-align:left">
130 * <td><b><code>text</code></b>
131 * <td>All buttons
132 * <td><code>NAME</code>
133 * <td>If you do not want the text of the button to mirror that
134 * of the <code>Action</code>, set the property
135 * <code>hideActionText</code> to <code>true</code>. If
136 * <code>hideActionText</code> is <code>true</code>, setting the
137 * <code>Action</code> changes the text of the button to
138 * <code>null</code> and any changes to <code>NAME</code>
139 * are ignored. <code>hideActionText</code> is useful for
140 * tool bar buttons that typically only show an <code>Icon</code>.
141 * <code>JToolBar.add(Action)</code> sets the property to
142 * <code>true</code> if the <code>Action</code> has a
143 * non-<code>null</code> value for <code>LARGE_ICON_KEY</code> or
144 * <code>SMALL_ICON</code>.
145 * <tr valign="top" style="text-align:left">
146 * <td><b><code>displayedMnemonicIndex</code></b>
147 * <td>All buttons
148 * <td><code>DISPLAYED_MNEMONIC_INDEX_KEY</code>
149 * <td>If the value of <code>DISPLAYED_MNEMONIC_INDEX_KEY</code> is
150 * beyond the bounds of the text, it is ignored. When
151 * <code>setAction</code> is called, if the value from the
152 * <code>Action</code> is <code>null</code>, the displayed
153 * mnemonic index is not updated. In any subsequent changes to
154 * <code>DISPLAYED_MNEMONIC_INDEX_KEY</code>, <code>null</code>
155 * is treated as -1.
156 * <tr valign="top" style="text-align:left">
157 * <td><b><code>icon</code></b>
158 * <td>All buttons except of <code>JCheckBox</code>,
159 * <code>JToggleButton</code> and <code>JRadioButton</code>.
160 * <td>either <code>LARGE_ICON_KEY</code> or
161 * <code>SMALL_ICON</code>
162 * <td>The <code>JMenuItem</code> subclasses only use
163 * <code>SMALL_ICON</code>. All other buttons will use
164 * <code>LARGE_ICON_KEY</code>; if the value is <code>null</code> they
165 * use <code>SMALL_ICON</code>.
166 * <tr valign="top" style="text-align:left">
167 * <td><b><code>accelerator</code></b>
168 * <td>All <code>JMenuItem</code> subclasses, with the exception of
169 * <code>JMenu</code>.
170 * <td><code>ACCELERATOR_KEY</code>
171 * <td>
172 * <tr valign="top" style="text-align:left">
173 * <td><b><code>selected</code></b>
174 * <td><code>JToggleButton</code>, <code>JCheckBox</code>,
175 * <code>JRadioButton</code>, <code>JCheckBoxMenuItem</code> and
176 * <code>JRadioButtonMenuItem</code>
177 * <td><code>SELECTED_KEY</code>
178 * <td>Components that honor this property only use
179 * the value if it is {@code non-null}. For example, if
180 * you set an {@code Action} that has a {@code null}
181 * value for {@code SELECTED_KEY} on a {@code JToggleButton}, the
182 * {@code JToggleButton} will not update it's selected state in
183 * any way. Similarly, any time the {@code JToggleButton}'s
184 * selected state changes it will only set the value back on
185 * the {@code Action} if the {@code Action} has a {@code non-null}
186 * value for {@code SELECTED_KEY}.
187 * <br>
188 * Components that honor this property keep their selected state
189 * in sync with this property. When the same {@code Action} is used
190 * with multiple components, all the components keep their selected
191 * state in sync with this property. Mutually exclusive
192 * buttons, such as {@code JToggleButton}s in a {@code ButtonGroup},
193 * force only one of the buttons to be selected. As such, do not
194 * use the same {@code Action} that defines a value for the
195 * {@code SELECTED_KEY} property with multiple mutually
196 * exclusive buttons.
197 * </tbody>
198 * </table>
199 * <p>
200 * <code>JPopupMenu</code>, <code>JToolBar</code> and <code>JMenu</code>
201 * all provide convenience methods for creating a component and setting the
202 * <code>Action</code> on the corresponding component. Refer to each of
203 * these classes for more information.
204 * <p>
205 * <code>Action</code> uses <code>PropertyChangeListener</code> to
206 * inform listeners the <code>Action</code> has changed. The beans
207 * specification indicates that a <code>null</code> property name can
208 * be used to indicate multiple values have changed. By default Swing
209 * components that take an <code>Action</code> do not handle such a
210 * change. To indicate that Swing should treat <code>null</code>
211 * according to the beans specification set the system property
212 * <code>swing.actions.reconfigureOnNull</code> to the <code>String</code>
213 * value <code>true</code>.
214 *
215 * @author Georges Saab
216 * @see AbstractAction
217 * @since 1.2
218 */
219 public interface Action extends ActionListener {
220 /**
221 * Useful constants that can be used as the storage-retrieval key
222 * when setting or getting one of this object's properties (text
223 * or icon).
224 */
225 /**
226 * Not currently used.
227 */
228 public static final String DEFAULT = "Default";
229 /**
230 * The key used for storing the <code>String</code> name
231 * for the action, used for a menu or button.
232 */
233 public static final String NAME = "Name";
234 /**
235 * The key used for storing a short <code>String</code>
236 * description for the action, used for tooltip text.
237 */
238 public static final String SHORT_DESCRIPTION = "ShortDescription";
239 /**
240 * The key used for storing a longer <code>String</code>
241 * description for the action, could be used for context-sensitive help.
242 */
243 public static final String LONG_DESCRIPTION = "LongDescription";
244 /**
245 * The key used for storing a small <code>Icon</code>, such
246 * as <code>ImageIcon</code>. This is typically used with
247 * menus such as <code>JMenuItem</code>.
248 * <p>
249 * If the same <code>Action</code> is used with menus and buttons you'll
250 * typically specify both a <code>SMALL_ICON</code> and a
251 * <code>LARGE_ICON_KEY</code>. The menu will use the
252 * <code>SMALL_ICON</code> and the button will use the
253 * <code>LARGE_ICON_KEY</code>.
254 */
255 public static final String SMALL_ICON = "SmallIcon";
256
257 /**
258 * The key used to determine the command <code>String</code> for the
259 * <code>ActionEvent</code> that will be created when an
260 * <code>Action</code> is going to be notified as the result of
261 * residing in a <code>Keymap</code> associated with a
262 * <code>JComponent</code>.
263 */
264 public static final String ACTION_COMMAND_KEY = "ActionCommandKey";
265
266 /**
267 * The key used for storing a <code>KeyStroke</code> to be used as the
268 * accelerator for the action.
269 *
270 * @since 1.3
271 */
272 public static final String ACCELERATOR_KEY="AcceleratorKey";
273
274 /**
275 * The key used for storing an <code>Integer</code> that corresponds to
276 * one of the <code>KeyEvent</code> key codes. The value is
277 * commonly used to specify a mnemonic. For example:
278 * <code>myAction.putValue(Action.MNEMONIC_KEY, KeyEvent.VK_A)</code>
279 * sets the mnemonic of <code>myAction</code> to 'a', while
280 * <code>myAction.putValue(Action.MNEMONIC_KEY, KeyEvent.getExtendedKeyCodeForChar('\u0444'))</code>
281 * sets the mnemonic of <code>myAction</code> to Cyrillic letter "Ef".
282 *
283 * @since 1.3
284 */
285 public static final String MNEMONIC_KEY="MnemonicKey";
286
287 /**
288 * The key used for storing a <code>Boolean</code> that corresponds
289 * to the selected state. This is typically used only for components
290 * that have a meaningful selection state. For example,
291 * <code>JRadioButton</code> and <code>JCheckBox</code> make use of
292 * this but instances of <code>JMenu</code> don't.
293 * <p>
294 * This property differs from the others in that it is both read
295 * by the component and set by the component. For example,
296 * if an <code>Action</code> is attached to a <code>JCheckBox</code>
297 * the selected state of the <code>JCheckBox</code> will be set from
298 * that of the <code>Action</code>. If the user clicks on the
299 * <code>JCheckBox</code> the selected state of the <code>JCheckBox</code>
300 * <b>and</b> the <code>Action</code> will <b>both</b> be updated.
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 * @since 1.6
306 */
307 public static final String SELECTED_KEY = "SwingSelectedKey";
308
309 /**
310 * The key used for storing an <code>Integer</code> that corresponds
311 * to the index in the text (identified by the <code>NAME</code>
312 * property) that the decoration for a mnemonic should be rendered at. If
313 * the value of this property is greater than or equal to the length of
314 * the text, it will treated as -1.
315 * <p>
316 * Note: the value of this field is prefixed with 'Swing' to
317 * avoid possible collisions with existing <code>Actions</code>.
318 *
319 * @see AbstractButton#setDisplayedMnemonicIndex
320 * @since 1.6
321 */
322 public static final String DISPLAYED_MNEMONIC_INDEX_KEY =
323 "SwingDisplayedMnemonicIndexKey";
324
325 /**
326 * The key used for storing an <code>Icon</code>. This is typically
327 * used by buttons, such as <code>JButton</code> and
328 * <code>JToggleButton</code>.
329 * <p>
330 * If the same <code>Action</code> is used with menus and buttons you'll
331 * typically specify both a <code>SMALL_ICON</code> and a
332 * <code>LARGE_ICON_KEY</code>. The menu will use the
333 * <code>SMALL_ICON</code> and the button the <code>LARGE_ICON_KEY</code>.
334 * <p>
335 * Note: the value of this field is prefixed with 'Swing' to
336 * avoid possible collisions with existing <code>Actions</code>.
337 *
338 * @since 1.6
339 */
340 public static final String LARGE_ICON_KEY = "SwingLargeIconKey";
341
342 /**
343 * Gets one of this object's properties
344 * using the associated key.
345 *
346 * @param key a {@code String} containing the key
347 * @return the {@code Object} value
348 * @see #putValue
349 */
350 public Object getValue(String key);
351 /**
352 * Sets one of this object's properties
353 * using the associated key. If the value has
354 * changed, a <code>PropertyChangeEvent</code> is sent
355 * to listeners.
356 *
357 * @param key a <code>String</code> containing the key
358 * @param value an <code>Object</code> value
359 */
360 public void putValue(String key, Object value);
361
362 /**
363 * Sets the enabled state of the {@code Action}. When enabled,
364 * any component associated with this object is active and
365 * able to fire this object's {@code actionPerformed} method.
366 * If the value has changed, a {@code PropertyChangeEvent} is sent
367 * to listeners.
368 *
369 * @param b true to enable this {@code Action}, false to disable it
370 * @see #accept
371 */
372 public void setEnabled(boolean b);
373 /**
374 * Returns the enabled state of the {@code Action}. When enabled,
375 * any component associated with this object is active and
376 * able to fire this object's {@code actionPerformed} method.
377 *
378 * @return true if this {@code Action} is enabled
379 * @see #accept
380 */
381 public boolean isEnabled();
382
383 /**
384 * Determines whether the action should be performed with the specified
385 * sender object. The {@code sender} can be {@code null}.
386 * The method must return false if the action is disabled.
387 * <p>
388 * @param sender the object to check, can be null
389 * @return {@code true} if the action should be performed with the sender
390 * object, must be false if the action is disabled.
391 * @see #isEnabled
392 * @see #setEnabled
393 */
394 default boolean accept(Object sender) {
395 return isEnabled();
396 }
397
398 /**
399 * Adds a <code>PropertyChange</code> listener. Containers and attached
400 * components use these methods to register interest in this
401 * <code>Action</code> object. When its enabled state or other property
402 * changes, the registered listeners are informed of the change.
403 *
404 * @param listener a <code>PropertyChangeListener</code> object
405 */
406 public void addPropertyChangeListener(PropertyChangeListener listener);
407 /**
408 * Removes a <code>PropertyChange</code> listener.
409 *
410 * @param listener a <code>PropertyChangeListener</code> object
411 * @see #addPropertyChangeListener
412 */
413 public void removePropertyChangeListener(PropertyChangeListener listener);
414
415 }