1 /*
2 * Copyright (c) 1995, 2014, Oracle and/or its affiliates. All rights reserved.
3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
4 *
5 * This code is free software; you can redistribute it and/or modify it
6 * under the terms of the GNU General Public License version 2 only, as
7 * published by the Free Software Foundation. Oracle designates this
8 * particular file as subject to the "Classpath" exception as provided
9 * by Oracle in the LICENSE file that accompanied this code.
10 *
11 * This code is distributed in the hope that it will be useful, but WITHOUT
12 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
13 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
14 * version 2 for more details (a copy is included in the LICENSE file that
15 * accompanied this code).
16 *
17 * You should have received a copy of the GNU General Public License version
18 * 2 along with this work; if not, write to the Free Software Foundation,
19 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
20 *
21 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
22 * or visit www.oracle.com if you need additional information or have any
23 * questions.
24 */
25
26 package java.awt;
27
28 import java.awt.peer.ButtonPeer;
29 import java.util.EventListener;
30 import java.awt.event.*;
31 import java.io.ObjectOutputStream;
32 import java.io.ObjectInputStream;
33 import java.io.IOException;
34 import javax.accessibility.*;
35
36 /**
37 * This class creates a labeled button. The application can cause
38 * some action to happen when the button is pushed. This image
39 * depicts three views of a "<code>Quit</code>" button as it appears
40 * under the Solaris operating system:
41 * <p>
42 * <img src="doc-files/Button-1.gif" alt="The following context describes the graphic"
43 * style="float:center; margin: 7px 10px;">
44 * <p>
45 * The first view shows the button as it appears normally.
46 * The second view shows the button
47 * when it has input focus. Its outline is darkened to let the
48 * user know that it is an active object. The third view shows the
49 * button when the user clicks the mouse over the button, and thus
50 * requests that an action be performed.
51 * <p>
52 * The gesture of clicking on a button with the mouse
53 * is associated with one instance of <code>ActionEvent</code>,
54 * which is sent out when the mouse is both pressed and released
55 * over the button. If an application is interested in knowing
56 * when the button has been pressed but not released, as a separate
57 * gesture, it can specialize <code>processMouseEvent</code>,
58 * or it can register itself as a listener for mouse events by
59 * calling <code>addMouseListener</code>. Both of these methods are
60 * defined by <code>Component</code>, the abstract superclass of
61 * all components.
62 * <p>
63 * When a button is pressed and released, AWT sends an instance
64 * of <code>ActionEvent</code> to the button, by calling
65 * <code>processEvent</code> on the button. The button's
66 * <code>processEvent</code> method receives all events
67 * for the button; it passes an action event along by
68 * calling its own <code>processActionEvent</code> method.
69 * The latter method passes the action event on to any action
70 * listeners that have registered an interest in action
71 * events generated by this button.
72 * <p>
73 * If an application wants to perform some action based on
74 * a button being pressed and released, it should implement
75 * <code>ActionListener</code> and register the new listener
76 * to receive events from this button, by calling the button's
77 * <code>addActionListener</code> method. The application can
78 * make use of the button's action command as a messaging protocol.
79 *
80 * @author Sami Shaio
81 * @see java.awt.event.ActionEvent
82 * @see java.awt.event.ActionListener
83 * @see java.awt.Component#processMouseEvent
84 * @see java.awt.Component#addMouseListener
85 * @since JDK1.0
86 */
87 public class Button extends Component implements Accessible {
88
89 /**
90 * The button's label. This value may be null.
91 * @serial
92 * @see #getLabel()
93 * @see #setLabel(String)
94 */
95 String label;
96
97 /**
98 * The action to be performed once a button has been
99 * pressed. This value may be null.
100 * @serial
101 * @see #getActionCommand()
102 * @see #setActionCommand(String)
103 */
104 String actionCommand;
105
106 transient ActionListener actionListener;
107
108 private static final String base = "button";
109 private static int nameCounter = 0;
110
111 /*
112 * JDK 1.1 serialVersionUID
113 */
114 private static final long serialVersionUID = -8774683716313001058L;
115
116
117 static {
118 /* ensure that the necessary native libraries are loaded */
119 Toolkit.loadLibraries();
120 if (!GraphicsEnvironment.isHeadless()) {
121 initIDs();
122 }
123 }
124
125 /**
126 * Initialize JNI field and method IDs for fields that may be
127 * accessed from C.
128 */
129 private static native void initIDs();
130
131 /**
132 * Constructs a button with an empty string for its label.
133 *
134 * @exception HeadlessException if GraphicsEnvironment.isHeadless()
135 * returns true
136 * @see java.awt.GraphicsEnvironment#isHeadless
137 */
138 public Button() throws HeadlessException {
139 this("");
140 }
141
142 /**
143 * Constructs a button with the specified label.
144 *
145 * @param label a string label for the button, or
146 * <code>null</code> for no label
147 * @exception HeadlessException if GraphicsEnvironment.isHeadless()
148 * returns true
149 * @see java.awt.GraphicsEnvironment#isHeadless
150 */
151 public Button(String label) throws HeadlessException {
152 GraphicsEnvironment.checkHeadless();
153 this.label = label;
154 }
155
156 /**
157 * Construct a name for this component. Called by getName() when the
158 * name is null.
159 */
160 String constructComponentName() {
161 synchronized (Button.class) {
162 return base + nameCounter++;
163 }
164 }
165
166 /**
167 * Creates the peer of the button. The button's peer allows the
168 * application to change the look of the button without changing
169 * its functionality.
170 *
171 * @see java.awt.Toolkit#createButton(java.awt.Button)
172 * @see java.awt.Component#getToolkit()
173 */
174 public void addNotify() {
175 synchronized(getTreeLock()) {
176 if (peer == null)
177 peer = getToolkit().createButton(this);
178 super.addNotify();
179 }
180 }
181
182 /**
183 * Gets the label of this button.
184 *
185 * @return the button's label, or <code>null</code>
186 * if the button has no label.
187 * @see java.awt.Button#setLabel
188 */
189 public String getLabel() {
190 return label;
191 }
192
193 /**
194 * Sets the button's label to be the specified string.
195 *
196 * @param label the new label, or <code>null</code>
197 * if the button has no label.
198 * @see java.awt.Button#getLabel
199 */
200 public void setLabel(String label) {
201 boolean testvalid = false;
202
203 synchronized (this) {
204 if (label != this.label && (this.label == null ||
205 !this.label.equals(label))) {
206 this.label = label;
207 ButtonPeer peer = (ButtonPeer)this.peer;
208 if (peer != null) {
209 peer.setLabel(label);
210 }
211 testvalid = true;
212 }
213 }
214
215 // This could change the preferred size of the Component.
216 if (testvalid) {
217 invalidateIfValid();
218 }
219 }
220
221 /**
222 * Sets the command name for the action event fired
223 * by this button. By default this action command is
224 * set to match the label of the button.
225 *
226 * @param command a string used to set the button's
227 * action command.
228 * If the string is <code>null</code> then the action command
229 * is set to match the label of the button.
230 * @see java.awt.event.ActionEvent
231 * @since JDK1.1
232 */
233 public void setActionCommand(String command) {
234 actionCommand = command;
235 }
236
237 /**
238 * Returns the command name of the action event fired by this button.
239 * If the command name is <code>null</code> (default) then this method
240 * returns the label of the button.
241 * @return the action command name (or label) for this button
242 */
243 public String getActionCommand() {
244 return (actionCommand == null? label : actionCommand);
245 }
246
247 /**
248 * Adds the specified action listener to receive action events from
249 * this button. Action events occur when a user presses or releases
250 * the mouse over this button.
251 * If l is null, no exception is thrown and no action is performed.
252 * <p>Refer to <a href="doc-files/AWTThreadIssues.html#ListenersThreads"
253 * >AWT Threading Issues</a> for details on AWT's threading model.
254 *
255 * @param l the action listener
256 * @see #removeActionListener
257 * @see #getActionListeners
258 * @see java.awt.event.ActionListener
259 * @since JDK1.1
260 */
261 public synchronized void addActionListener(ActionListener l) {
262 if (l == null) {
263 return;
264 }
265 actionListener = AWTEventMulticaster.add(actionListener, l);
266 newEventsOnly = true;
267 }
268
269 /**
270 * Removes the specified action listener so that it no longer
271 * receives action events from this button. Action events occur
272 * when a user presses or releases the mouse over this button.
273 * If l is null, no exception is thrown and no action is performed.
274 * <p>Refer to <a href="doc-files/AWTThreadIssues.html#ListenersThreads"
275 * >AWT Threading Issues</a> for details on AWT's threading model.
276 *
277 * @param l the action listener
278 * @see #addActionListener
279 * @see #getActionListeners
280 * @see java.awt.event.ActionListener
281 * @since JDK1.1
282 */
283 public synchronized void removeActionListener(ActionListener l) {
284 if (l == null) {
285 return;
286 }
287 actionListener = AWTEventMulticaster.remove(actionListener, l);
288 }
289
290 /**
291 * Returns an array of all the action listeners
292 * registered on this button.
293 *
294 * @return all of this button's <code>ActionListener</code>s
295 * or an empty array if no action
296 * listeners are currently registered
297 *
298 * @see #addActionListener
299 * @see #removeActionListener
300 * @see java.awt.event.ActionListener
301 * @since 1.4
302 */
303 public synchronized ActionListener[] getActionListeners() {
304 return getListeners(ActionListener.class);
305 }
306
307 /**
308 * Returns an array of all the objects currently registered
309 * as <code><em>Foo</em>Listener</code>s
310 * upon this <code>Button</code>.
311 * <code><em>Foo</em>Listener</code>s are registered using the
312 * <code>add<em>Foo</em>Listener</code> method.
313 *
314 * <p>
315 * You can specify the <code>listenerType</code> argument
316 * with a class literal, such as
317 * <code><em>Foo</em>Listener.class</code>.
318 * For example, you can query a
319 * <code>Button</code> <code>b</code>
320 * for its action listeners with the following code:
321 *
322 * <pre>ActionListener[] als = (ActionListener[])(b.getListeners(ActionListener.class));</pre>
323 *
324 * If no such listeners exist, this method returns an empty array.
325 *
326 * @param listenerType the type of listeners requested; this parameter
327 * should specify an interface that descends from
328 * <code>java.util.EventListener</code>
329 * @return an array of all objects registered as
330 * <code><em>Foo</em>Listener</code>s on this button,
331 * or an empty array if no such
332 * listeners have been added
333 * @exception ClassCastException if <code>listenerType</code>
334 * doesn't specify a class or interface that implements
335 * <code>java.util.EventListener</code>
336 *
337 * @see #getActionListeners
338 * @since 1.3
339 */
340 public <T extends EventListener> T[] getListeners(Class<T> listenerType) {
341 EventListener l = null;
342 if (listenerType == ActionListener.class) {
343 l = actionListener;
344 } else {
345 return super.getListeners(listenerType);
346 }
347 return AWTEventMulticaster.getListeners(l, listenerType);
348 }
349
350 // REMIND: remove when filtering is done at lower level
351 boolean eventEnabled(AWTEvent e) {
352 if (e.id == ActionEvent.ACTION_PERFORMED) {
353 if ((eventMask & AWTEvent.ACTION_EVENT_MASK) != 0 ||
354 actionListener != null) {
355 return true;
356 }
357 return false;
358 }
359 return super.eventEnabled(e);
360 }
361
362 /**
363 * Processes events on this button. If an event is
364 * an instance of <code>ActionEvent</code>, this method invokes
365 * the <code>processActionEvent</code> method. Otherwise,
366 * it invokes <code>processEvent</code> on the superclass.
367 * <p>Note that if the event parameter is <code>null</code>
368 * the behavior is unspecified and may result in an
369 * exception.
370 *
371 * @param e the event
372 * @see java.awt.event.ActionEvent
373 * @see java.awt.Button#processActionEvent
374 * @since JDK1.1
375 */
376 protected void processEvent(AWTEvent e) {
377 if (e instanceof ActionEvent) {
378 processActionEvent((ActionEvent)e);
379 return;
380 }
381 super.processEvent(e);
382 }
383
384 /**
385 * Processes action events occurring on this button
386 * by dispatching them to any registered
387 * <code>ActionListener</code> objects.
388 * <p>
389 * This method is not called unless action events are
390 * enabled for this button. Action events are enabled
391 * when one of the following occurs:
392 * <ul>
393 * <li>An <code>ActionListener</code> object is registered
394 * via <code>addActionListener</code>.
395 * <li>Action events are enabled via <code>enableEvents</code>.
396 * </ul>
397 * <p>Note that if the event parameter is <code>null</code>
398 * the behavior is unspecified and may result in an
399 * exception.
400 *
401 * @param e the action event
402 * @see java.awt.event.ActionListener
403 * @see java.awt.Button#addActionListener
404 * @see java.awt.Component#enableEvents
405 * @since JDK1.1
406 */
407 protected void processActionEvent(ActionEvent e) {
408 ActionListener listener = actionListener;
409 if (listener != null) {
410 listener.actionPerformed(e);
411 }
412 }
413
414 /**
415 * Returns a string representing the state of this <code>Button</code>.
416 * This method is intended to be used only for debugging purposes, and the
417 * content and format of the returned string may vary between
418 * implementations. The returned string may be empty but may not be
419 * <code>null</code>.
420 *
421 * @return the parameter string of this button
422 */
423 protected String paramString() {
424 return super.paramString() + ",label=" + label;
425 }
426
427
428 /* Serialization support.
429 */
430
431 /*
432 * Button Serial Data Version.
433 * @serial
434 */
435 private int buttonSerializedDataVersion = 1;
436
437 /**
438 * Writes default serializable fields to stream. Writes
439 * a list of serializable <code>ActionListeners</code>
440 * as optional data. The non-serializable
441 * <code>ActionListeners</code> are detected and
442 * no attempt is made to serialize them.
443 *
444 * @serialData <code>null</code> terminated sequence of 0 or
445 * more pairs: the pair consists of a <code>String</code>
446 * and an <code>Object</code>; the <code>String</code>
447 * indicates the type of object and is one of the following:
448 * <code>actionListenerK</code> indicating an
449 * <code>ActionListener</code> object
450 *
451 * @param s the <code>ObjectOutputStream</code> to write
452 * @see AWTEventMulticaster#save(ObjectOutputStream, String, EventListener)
453 * @see java.awt.Component#actionListenerK
454 * @see #readObject(ObjectInputStream)
455 */
456 private void writeObject(ObjectOutputStream s)
457 throws IOException
458 {
459 s.defaultWriteObject();
460
461 AWTEventMulticaster.save(s, actionListenerK, actionListener);
462 s.writeObject(null);
463 }
464
465 /**
466 * Reads the <code>ObjectInputStream</code> and if
467 * it isn't <code>null</code> adds a listener to
468 * receive action events fired by the button.
469 * Unrecognized keys or values will be ignored.
470 *
471 * @param s the <code>ObjectInputStream</code> to read
472 * @exception HeadlessException if
473 * <code>GraphicsEnvironment.isHeadless</code> returns
474 * <code>true</code>
475 * @serial
476 * @see #removeActionListener(ActionListener)
477 * @see #addActionListener(ActionListener)
478 * @see java.awt.GraphicsEnvironment#isHeadless
479 * @see #writeObject(ObjectOutputStream)
480 */
481 private void readObject(ObjectInputStream s)
482 throws ClassNotFoundException, IOException, HeadlessException
483 {
484 GraphicsEnvironment.checkHeadless();
485 s.defaultReadObject();
486
487 Object keyOrNull;
488 while(null != (keyOrNull = s.readObject())) {
489 String key = ((String)keyOrNull).intern();
490
491 if (actionListenerK == key)
492 addActionListener((ActionListener)(s.readObject()));
493
494 else // skip value for unrecognized key
495 s.readObject();
496 }
497 }
498
499
500 /////////////////
501 // Accessibility support
502 ////////////////
503
504 /**
505 * Gets the <code>AccessibleContext</code> associated with
506 * this <code>Button</code>. For buttons, the
507 * <code>AccessibleContext</code> takes the form of an
508 * <code>AccessibleAWTButton</code>.
509 * A new <code>AccessibleAWTButton</code> instance is
510 * created if necessary.
511 *
512 * @return an <code>AccessibleAWTButton</code> that serves as the
513 * <code>AccessibleContext</code> of this <code>Button</code>
514 * @beaninfo
515 * expert: true
516 * description: The AccessibleContext associated with this Button.
517 * @since 1.3
518 */
519 public AccessibleContext getAccessibleContext() {
520 if (accessibleContext == null) {
521 accessibleContext = new AccessibleAWTButton();
522 }
523 return accessibleContext;
524 }
525
526 /**
527 * This class implements accessibility support for the
528 * <code>Button</code> class. It provides an implementation of the
529 * Java Accessibility API appropriate to button user-interface elements.
530 * @since 1.3
531 */
532 protected class AccessibleAWTButton extends AccessibleAWTComponent
533 implements AccessibleAction, AccessibleValue
534 {
535 /*
536 * JDK 1.3 serialVersionUID
537 */
538 private static final long serialVersionUID = -5932203980244017102L;
539
540 /**
541 * Get the accessible name of this object.
542 *
543 * @return the localized name of the object -- can be null if this
544 * object does not have a name
545 */
546 public String getAccessibleName() {
547 if (accessibleName != null) {
548 return accessibleName;
549 } else {
550 if (getLabel() == null) {
551 return super.getAccessibleName();
552 } else {
553 return getLabel();
554 }
555 }
556 }
557
558 /**
559 * Get the AccessibleAction associated with this object. In the
560 * implementation of the Java Accessibility API for this class,
561 * return this object, which is responsible for implementing the
562 * AccessibleAction interface on behalf of itself.
563 *
564 * @return this object
565 */
566 public AccessibleAction getAccessibleAction() {
567 return this;
568 }
569
570 /**
571 * Get the AccessibleValue associated with this object. In the
572 * implementation of the Java Accessibility API for this class,
573 * return this object, which is responsible for implementing the
574 * AccessibleValue interface on behalf of itself.
575 *
576 * @return this object
577 */
578 public AccessibleValue getAccessibleValue() {
579 return this;
580 }
581
582 /**
583 * Returns the number of Actions available in this object. The
584 * default behavior of a button is to have one action - toggle
585 * the button.
586 *
587 * @return 1, the number of Actions in this object
588 */
589 public int getAccessibleActionCount() {
590 return 1;
591 }
592
593 /**
594 * Return a description of the specified action of the object.
595 *
596 * @param i zero-based index of the actions
597 */
598 public String getAccessibleActionDescription(int i) {
599 if (i == 0) {
600 // [[[PENDING: WDW -- need to provide a localized string]]]
601 return "click";
602 } else {
603 return null;
604 }
605 }
606
607 /**
608 * Perform the specified Action on the object
609 *
610 * @param i zero-based index of actions
611 * @return true if the the action was performed; else false.
612 */
613 public boolean doAccessibleAction(int i) {
614 if (i == 0) {
615 // Simulate a button click
616 Toolkit.getEventQueue().postEvent(
617 new ActionEvent(Button.this,
618 ActionEvent.ACTION_PERFORMED,
619 Button.this.getActionCommand()));
620 return true;
621 } else {
622 return false;
623 }
624 }
625
626 /**
627 * Get the value of this object as a Number.
628 *
629 * @return An Integer of 0 if this isn't selected or an Integer of 1 if
630 * this is selected.
631 * @see javax.swing.AbstractButton#isSelected()
632 */
633 public Number getCurrentAccessibleValue() {
634 return Integer.valueOf(0);
635 }
636
637 /**
638 * Set the value of this object as a Number.
639 *
640 * @return True if the value was set.
641 */
642 public boolean setCurrentAccessibleValue(Number n) {
643 return false;
644 }
645
646 /**
647 * Get the minimum value of this object as a Number.
648 *
649 * @return An Integer of 0.
650 */
651 public Number getMinimumAccessibleValue() {
652 return Integer.valueOf(0);
653 }
654
655 /**
656 * Get the maximum value of this object as a Number.
657 *
658 * @return An Integer of 0.
659 */
660 public Number getMaximumAccessibleValue() {
661 return Integer.valueOf(0);
662 }
663
664 /**
665 * Get the role of this object.
666 *
667 * @return an instance of AccessibleRole describing the role of the
668 * object
669 * @see AccessibleRole
670 */
671 public AccessibleRole getAccessibleRole() {
672 return AccessibleRole.PUSH_BUTTON;
673 }
674 } // inner class AccessibleAWTButton
675
676 }