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 *
242 * @return the action command name (or label) for this button
243 */
244 public String getActionCommand() {
245 return (actionCommand == null? label : actionCommand);
246 }
247
248 /**
249 * Adds the specified action listener to receive action events from
250 * this button. Action events occur when a user presses or releases
251 * the mouse over this button.
252 * If l is null, no exception is thrown and no action is performed.
253 * <p>Refer to <a href="doc-files/AWTThreadIssues.html#ListenersThreads"
254 * >AWT Threading Issues</a> for details on AWT's threading model.
255 *
256 * @param l the action listener
257 * @see #removeActionListener
258 * @see #getActionListeners
259 * @see java.awt.event.ActionListener
260 * @since JDK1.1
261 */
262 public synchronized void addActionListener(ActionListener l) {
263 if (l == null) {
264 return;
265 }
266 actionListener = AWTEventMulticaster.add(actionListener, l);
267 newEventsOnly = true;
268 }
269
270 /**
271 * Removes the specified action listener so that it no longer
272 * receives action events from this button. Action events occur
273 * when a user presses or releases the mouse over this button.
274 * If l is null, no exception is thrown and no action is performed.
275 * <p>Refer to <a href="doc-files/AWTThreadIssues.html#ListenersThreads"
276 * >AWT Threading Issues</a> for details on AWT's threading model.
277 *
278 * @param l the action listener
279 * @see #addActionListener
280 * @see #getActionListeners
281 * @see java.awt.event.ActionListener
282 * @since JDK1.1
283 */
284 public synchronized void removeActionListener(ActionListener l) {
285 if (l == null) {
286 return;
287 }
288 actionListener = AWTEventMulticaster.remove(actionListener, l);
289 }
290
291 /**
292 * Returns an array of all the action listeners
293 * registered on this button.
294 *
295 * @return all of this button's <code>ActionListener</code>s
296 * or an empty array if no action
297 * listeners are currently registered
298 *
299 * @see #addActionListener
300 * @see #removeActionListener
301 * @see java.awt.event.ActionListener
302 * @since 1.4
303 */
304 public synchronized ActionListener[] getActionListeners() {
305 return getListeners(ActionListener.class);
306 }
307
308 /**
309 * Returns an array of all the objects currently registered
310 * as <code><em>Foo</em>Listener</code>s
311 * upon this <code>Button</code>.
312 * <code><em>Foo</em>Listener</code>s are registered using the
313 * <code>add<em>Foo</em>Listener</code> method.
314 *
315 * <p>
316 * You can specify the <code>listenerType</code> argument
317 * with a class literal, such as
318 * <code><em>Foo</em>Listener.class</code>.
319 * For example, you can query a
320 * <code>Button</code> <code>b</code>
321 * for its action listeners with the following code:
322 *
323 * <pre>ActionListener[] als = (ActionListener[])(b.getListeners(ActionListener.class));</pre>
324 *
325 * If no such listeners exist, this method returns an empty array.
326 *
327 * @param listenerType the type of listeners requested; this parameter
328 * should specify an interface that descends from
329 * <code>java.util.EventListener</code>
330 * @return an array of all objects registered as
331 * <code><em>Foo</em>Listener</code>s on this button,
332 * or an empty array if no such
333 * listeners have been added
334 * @exception ClassCastException if <code>listenerType</code>
335 * doesn't specify a class or interface that implements
336 * <code>java.util.EventListener</code>
337 *
338 * @see #getActionListeners
339 * @since 1.3
340 */
341 public <T extends EventListener> T[] getListeners(Class<T> listenerType) {
342 EventListener l = null;
343 if (listenerType == ActionListener.class) {
344 l = actionListener;
345 } else {
346 return super.getListeners(listenerType);
347 }
348 return AWTEventMulticaster.getListeners(l, listenerType);
349 }
350
351 // REMIND: remove when filtering is done at lower level
352 boolean eventEnabled(AWTEvent e) {
353 if (e.id == ActionEvent.ACTION_PERFORMED) {
354 if ((eventMask & AWTEvent.ACTION_EVENT_MASK) != 0 ||
355 actionListener != null) {
356 return true;
357 }
358 return false;
359 }
360 return super.eventEnabled(e);
361 }
362
363 /**
364 * Processes events on this button. If an event is
365 * an instance of <code>ActionEvent</code>, this method invokes
366 * the <code>processActionEvent</code> method. Otherwise,
367 * it invokes <code>processEvent</code> on the superclass.
368 * <p>Note that if the event parameter is <code>null</code>
369 * the behavior is unspecified and may result in an
370 * exception.
371 *
372 * @param e the event
373 * @see java.awt.event.ActionEvent
374 * @see java.awt.Button#processActionEvent
375 * @since JDK1.1
376 */
377 protected void processEvent(AWTEvent e) {
378 if (e instanceof ActionEvent) {
379 processActionEvent((ActionEvent)e);
380 return;
381 }
382 super.processEvent(e);
383 }
384
385 /**
386 * Processes action events occurring on this button
387 * by dispatching them to any registered
388 * <code>ActionListener</code> objects.
389 * <p>
390 * This method is not called unless action events are
391 * enabled for this button. Action events are enabled
392 * when one of the following occurs:
393 * <ul>
394 * <li>An <code>ActionListener</code> object is registered
395 * via <code>addActionListener</code>.
396 * <li>Action events are enabled via <code>enableEvents</code>.
397 * </ul>
398 * <p>Note that if the event parameter is <code>null</code>
399 * the behavior is unspecified and may result in an
400 * exception.
401 *
402 * @param e the action event
403 * @see java.awt.event.ActionListener
404 * @see java.awt.Button#addActionListener
405 * @see java.awt.Component#enableEvents
406 * @since JDK1.1
407 */
408 protected void processActionEvent(ActionEvent e) {
409 ActionListener listener = actionListener;
410 if (listener != null) {
411 listener.actionPerformed(e);
412 }
413 }
414
415 /**
416 * Returns a string representing the state of this <code>Button</code>.
417 * This method is intended to be used only for debugging purposes, and the
418 * content and format of the returned string may vary between
419 * implementations. The returned string may be empty but may not be
420 * <code>null</code>.
421 *
422 * @return the parameter string of this button
423 */
424 protected String paramString() {
425 return super.paramString() + ",label=" + label;
426 }
427
428
429 /* Serialization support.
430 */
431
432 /*
433 * Button Serial Data Version.
434 * @serial
435 */
436 private int buttonSerializedDataVersion = 1;
437
438 /**
439 * Writes default serializable fields to stream. Writes
440 * a list of serializable <code>ActionListeners</code>
441 * as optional data. The non-serializable
442 * <code>ActionListeners</code> are detected and
443 * no attempt is made to serialize them.
444 *
445 * @serialData <code>null</code> terminated sequence of 0 or
446 * more pairs: the pair consists of a <code>String</code>
447 * and an <code>Object</code>; the <code>String</code>
448 * indicates the type of object and is one of the following:
449 * <code>actionListenerK</code> indicating an
450 * <code>ActionListener</code> object
451 *
452 * @param s the <code>ObjectOutputStream</code> to write
453 * @see AWTEventMulticaster#save(ObjectOutputStream, String, EventListener)
454 * @see java.awt.Component#actionListenerK
455 * @see #readObject(ObjectInputStream)
456 */
457 private void writeObject(ObjectOutputStream s)
458 throws IOException
459 {
460 s.defaultWriteObject();
461
462 AWTEventMulticaster.save(s, actionListenerK, actionListener);
463 s.writeObject(null);
464 }
465
466 /**
467 * Reads the <code>ObjectInputStream</code> and if
468 * it isn't <code>null</code> adds a listener to
469 * receive action events fired by the button.
470 * Unrecognized keys or values will be ignored.
471 *
472 * @param s the <code>ObjectInputStream</code> to read
473 * @exception HeadlessException if
474 * <code>GraphicsEnvironment.isHeadless</code> returns
475 * <code>true</code>
476 * @serial
477 * @see #removeActionListener(ActionListener)
478 * @see #addActionListener(ActionListener)
479 * @see java.awt.GraphicsEnvironment#isHeadless
480 * @see #writeObject(ObjectOutputStream)
481 */
482 private void readObject(ObjectInputStream s)
483 throws ClassNotFoundException, IOException, HeadlessException
484 {
485 GraphicsEnvironment.checkHeadless();
486 s.defaultReadObject();
487
488 Object keyOrNull;
489 while(null != (keyOrNull = s.readObject())) {
490 String key = ((String)keyOrNull).intern();
491
492 if (actionListenerK == key)
493 addActionListener((ActionListener)(s.readObject()));
494
495 else // skip value for unrecognized key
496 s.readObject();
497 }
498 }
499
500
501 /////////////////
502 // Accessibility support
503 ////////////////
504
505 /**
506 * Gets the <code>AccessibleContext</code> associated with
507 * this <code>Button</code>. For buttons, the
508 * <code>AccessibleContext</code> takes the form of an
509 * <code>AccessibleAWTButton</code>.
510 * A new <code>AccessibleAWTButton</code> instance is
511 * created if necessary.
512 *
513 * @return an <code>AccessibleAWTButton</code> that serves as the
514 * <code>AccessibleContext</code> of this <code>Button</code>
515 * @beaninfo
516 * expert: true
517 * description: The AccessibleContext associated with this Button.
518 * @since 1.3
519 */
520 public AccessibleContext getAccessibleContext() {
521 if (accessibleContext == null) {
522 accessibleContext = new AccessibleAWTButton();
523 }
524 return accessibleContext;
525 }
526
527 /**
528 * This class implements accessibility support for the
529 * <code>Button</code> class. It provides an implementation of the
530 * Java Accessibility API appropriate to button user-interface elements.
531 * @since 1.3
532 */
533 protected class AccessibleAWTButton extends AccessibleAWTComponent
534 implements AccessibleAction, AccessibleValue
535 {
536 /*
537 * JDK 1.3 serialVersionUID
538 */
539 private static final long serialVersionUID = -5932203980244017102L;
540
541 /**
542 * Get the accessible name of this object.
543 *
544 * @return the localized name of the object -- can be null if this
545 * object does not have a name
546 */
547 public String getAccessibleName() {
548 if (accessibleName != null) {
549 return accessibleName;
550 } else {
551 if (getLabel() == null) {
552 return super.getAccessibleName();
553 } else {
554 return getLabel();
555 }
556 }
557 }
558
559 /**
560 * Get the AccessibleAction associated with this object. In the
561 * implementation of the Java Accessibility API for this class,
562 * return this object, which is responsible for implementing the
563 * AccessibleAction interface on behalf of itself.
564 *
565 * @return this object
566 */
567 public AccessibleAction getAccessibleAction() {
568 return this;
569 }
570
571 /**
572 * Get the AccessibleValue associated with this object. In the
573 * implementation of the Java Accessibility API for this class,
574 * return this object, which is responsible for implementing the
575 * AccessibleValue interface on behalf of itself.
576 *
577 * @return this object
578 */
579 public AccessibleValue getAccessibleValue() {
580 return this;
581 }
582
583 /**
584 * Returns the number of Actions available in this object. The
585 * default behavior of a button is to have one action - toggle
586 * the button.
587 *
588 * @return 1, the number of Actions in this object
589 */
590 public int getAccessibleActionCount() {
591 return 1;
592 }
593
594 /**
595 * Return a description of the specified action of the object.
596 *
597 * @param i zero-based index of the actions
598 */
599 public String getAccessibleActionDescription(int i) {
600 if (i == 0) {
601 // [[[PENDING: WDW -- need to provide a localized string]]]
602 return "click";
603 } else {
604 return null;
605 }
606 }
607
608 /**
609 * Perform the specified Action on the object
610 *
611 * @param i zero-based index of actions
612 * @return true if the the action was performed; else false.
613 */
614 public boolean doAccessibleAction(int i) {
615 if (i == 0) {
616 // Simulate a button click
617 Toolkit.getEventQueue().postEvent(
618 new ActionEvent(Button.this,
619 ActionEvent.ACTION_PERFORMED,
620 Button.this.getActionCommand()));
621 return true;
622 } else {
623 return false;
624 }
625 }
626
627 /**
628 * Get the value of this object as a Number.
629 *
630 * @return An Integer of 0 if this isn't selected or an Integer of 1 if
631 * this is selected.
632 * @see javax.swing.AbstractButton#isSelected()
633 */
634 public Number getCurrentAccessibleValue() {
635 return Integer.valueOf(0);
636 }
637
638 /**
639 * Set the value of this object as a Number.
640 *
641 * @return True if the value was set.
642 */
643 public boolean setCurrentAccessibleValue(Number n) {
644 return false;
645 }
646
647 /**
648 * Get the minimum value of this object as a Number.
649 *
650 * @return An Integer of 0.
651 */
652 public Number getMinimumAccessibleValue() {
653 return Integer.valueOf(0);
654 }
655
656 /**
657 * Get the maximum value of this object as a Number.
658 *
659 * @return An Integer of 0.
660 */
661 public Number getMaximumAccessibleValue() {
662 return Integer.valueOf(0);
663 }
664
665 /**
666 * Get the role of this object.
667 *
668 * @return an instance of AccessibleRole describing the role of the
669 * object
670 * @see AccessibleRole
671 */
672 public AccessibleRole getAccessibleRole() {
673 return AccessibleRole.PUSH_BUTTON;
674 }
675 } // inner class AccessibleAWTButton
676
677 }