1 /*
   2  * Copyright (c) 1997, 2011, 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 
  27 
  28 package javax.swing;
  29 
  30 
  31 
  32 import java.util.*;
  33 import java.util.concurrent.atomic.AtomicBoolean;
  34 import java.util.concurrent.locks.*;
  35 import java.awt.*;
  36 import java.awt.event.*;
  37 import java.io.Serializable;
  38 import java.io.*;
  39 import java.security.AccessControlContext;
  40 import java.security.AccessController;
  41 import java.security.PrivilegedAction;
  42 import javax.swing.event.EventListenerList;
  43 
  44 
  45 
  46 /**
  47  * Fires one or more {@code ActionEvent}s at specified
  48  * intervals. An example use is an animation object that uses a
  49  * <code>Timer</code> as the trigger for drawing its frames.
  50  *<p>
  51  * Setting up a timer
  52  * involves creating a <code>Timer</code> object,
  53  * registering one or more action listeners on it,
  54  * and starting the timer using
  55  * the <code>start</code> method.
  56  * For example,
  57  * the following code creates and starts a timer
  58  * that fires an action event once per second
  59  * (as specified by the first argument to the <code>Timer</code> constructor).
  60  * The second argument to the <code>Timer</code> constructor
  61  * specifies a listener to receive the timer's action events.
  62  *
  63  *<pre>
  64  *  int delay = 1000; //milliseconds
  65  *  ActionListener taskPerformer = new ActionListener() {
  66  *      public void actionPerformed(ActionEvent evt) {
  67  *          <em>//...Perform a task...</em>
  68  *      }
  69  *  };
  70  *  new Timer(delay, taskPerformer).start();</pre>
  71  *
  72  * <p>
  73  * {@code Timers} are constructed by specifying both a delay parameter
  74  * and an {@code ActionListener}. The delay parameter is used
  75  * to set both the initial delay and the delay between event
  76  * firing, in milliseconds. Once the timer has been started,
  77  * it waits for the initial delay before firing its
  78  * first <code>ActionEvent</code> to registered listeners.
  79  * After this first event, it continues to fire events
  80  * every time the between-event delay has elapsed, until it
  81  * is stopped.
  82  * <p>
  83  * After construction, the initial delay and the between-event
  84  * delay can be changed independently, and additional
  85  * <code>ActionListeners</code> may be added.
  86  * <p>
  87  * If you want the timer to fire only the first time and then stop,
  88  * invoke <code>setRepeats(false)</code> on the timer.
  89  * <p>
  90  * Although all <code>Timer</code>s perform their waiting
  91  * using a single, shared thread
  92  * (created by the first <code>Timer</code> object that executes),
  93  * the action event handlers for <code>Timer</code>s
  94  * execute on another thread -- the event-dispatching thread.
  95  * This means that the action handlers for <code>Timer</code>s
  96  * can safely perform operations on Swing components.
  97  * However, it also means that the handlers must execute quickly
  98  * to keep the GUI responsive.
  99  *
 100  * <p>
 101  * In v 1.3, another <code>Timer</code> class was added
 102  * to the Java platform: <code>java.util.Timer</code>.
 103  * Both it and <code>javax.swing.Timer</code>
 104  * provide the same basic functionality,
 105  * but <code>java.util.Timer</code>
 106  * is more general and has more features.
 107  * The <code>javax.swing.Timer</code> has two features
 108  * that can make it a little easier to use with GUIs.
 109  * First, its event handling metaphor is familiar to GUI programmers
 110  * and can make dealing with the event-dispatching thread
 111  * a bit simpler.
 112  * Second, its
 113  * automatic thread sharing means that you don't have to
 114  * take special steps to avoid spawning
 115  * too many threads.
 116  * Instead, your timer uses the same thread
 117  * used to make cursors blink,
 118  * tool tips appear,
 119  * and so on.
 120  *
 121  * <p>
 122  * You can find further documentation
 123  * and several examples of using timers by visiting
 124  * <a href="http://java.sun.com/docs/books/tutorial/uiswing/misc/timer.html"
 125  * target = "_top">How to Use Timers</a>,
 126  * a section in <em>The Java Tutorial.</em>
 127  * For more examples and help in choosing between
 128  * this <code>Timer</code> class and
 129  * <code>java.util.Timer</code>,
 130  * see
 131  * <a href="http://java.sun.com/products/jfc/tsc/articles/timer/"
 132  * target="_top">Using Timers in Swing Applications</a>,
 133  * an article in <em>The Swing Connection.</em>
 134  * <p>
 135  * <strong>Warning:</strong>
 136  * Serialized objects of this class will not be compatible with
 137  * future Swing releases. The current serialization support is
 138  * appropriate for short term storage or RMI between applications running
 139  * the same version of Swing.  As of 1.4, support for long term storage
 140  * of all JavaBeans<sup><font size="-2">TM</font></sup>
 141  * has been added to the <code>java.beans</code> package.
 142  * Please see {@link java.beans.XMLEncoder}.
 143  *
 144  * @see java.util.Timer <code>java.util.Timer</code>
 145  *
 146  *
 147  * @author Dave Moore
 148  */
 149 public class Timer implements Serializable
 150 {
 151     /*
 152      * NOTE: all fields need to be handled in readResolve
 153      */
 154 
 155     protected EventListenerList listenerList = new EventListenerList();
 156 
 157     // The following field strives to maintain the following:
 158     //    If coalesce is true, only allow one Runnable to be queued on the
 159     //    EventQueue and be pending (ie in the process of notifying the
 160     //    ActionListener). If we didn't do this it would allow for a
 161     //    situation where the app is taking too long to process the
 162     //    actionPerformed, and thus we'ld end up queing a bunch of Runnables
 163     //    and the app would never return: not good. This of course implies
 164     //    you can get dropped events, but such is life.
 165     // notify is used to indicate if the ActionListener can be notified, when
 166     // the Runnable is processed if this is true it will notify the listeners.
 167     // notify is set to true when the Timer fires and the Runnable is queued.
 168     // It will be set to false after notifying the listeners (if coalesce is
 169     // true) or if the developer invokes stop.
 170     private transient final AtomicBoolean notify = new AtomicBoolean(false);
 171 
 172     private volatile int     initialDelay, delay;
 173     private volatile boolean repeats = true, coalesce = true;
 174 
 175     private transient final Runnable doPostEvent;
 176 
 177     private static volatile boolean logTimers;
 178 
 179     private transient final Lock lock = new ReentrantLock();
 180 
 181     /*
 182      * The timer's AccessControlContext.
 183      */
 184      private transient volatile AccessControlContext acc =
 185             AccessController.getContext();
 186 
 187     /**
 188       * Returns the acc this timer was constructed with.
 189       */
 190      final AccessControlContext getAccessControlContext() {
 191        if (acc == null) {
 192            throw new SecurityException(
 193                    "Timer is missing AccessControlContext");
 194        }
 195        return acc;
 196      }
 197 
 198     // This field is maintained by TimerQueue.
 199     // eventQueued can also be reset by the TimerQueue, but will only ever
 200     // happen in applet case when TimerQueues thread is destroyed.
 201     // access to this field is synchronized on getLock() lock.
 202     transient TimerQueue.DelayedTimer delayedTimer = null;
 203 
 204     private volatile String actionCommand;
 205 
 206     /**
 207      * Creates a {@code Timer} and initializes both the initial delay and
 208      * between-event delay to {@code delay} milliseconds. If {@code delay}
 209      * is less than or equal to zero, the timer fires as soon as it
 210      * is started. If <code>listener</code> is not <code>null</code>,
 211      * it's registered as an action listener on the timer.
 212      *
 213      * @param delay milliseconds for the initial and between-event delay
 214      * @param listener  an initial listener; can be <code>null</code>
 215 
 216      * @see #addActionListener
 217      * @see #setInitialDelay
 218      * @see #setRepeats
 219      */
 220     public Timer(int delay, ActionListener listener) {
 221         super();
 222         this.delay = delay;
 223         this.initialDelay = delay;
 224 
 225         doPostEvent = new DoPostEvent();
 226 
 227         if (listener != null) {
 228             addActionListener(listener);
 229         }
 230     }
 231 
 232     /**
 233      * DoPostEvent is a runnable class that fires actionEvents to
 234      * the listeners on the EventDispatchThread, via invokeLater.
 235      * @see Timer#post
 236      */
 237     class DoPostEvent implements Runnable
 238     {
 239         public void run() {
 240             if (logTimers) {
 241                 System.out.println("Timer ringing: " + Timer.this);
 242             }
 243             if(notify.get()) {
 244                 fireActionPerformed(new ActionEvent(Timer.this, 0, getActionCommand(),
 245                                                     System.currentTimeMillis(),
 246                                                     0));
 247                 if (coalesce) {
 248                     cancelEvent();
 249                 }
 250             }
 251         }
 252 
 253         Timer getTimer() {
 254             return Timer.this;
 255         }
 256     }
 257 
 258     /**
 259      * Adds an action listener to the <code>Timer</code>.
 260      *
 261      * @param listener the listener to add
 262      *
 263      * @see #Timer
 264      */
 265     public void addActionListener(ActionListener listener) {
 266         listenerList.add(ActionListener.class, listener);
 267     }
 268 
 269 
 270     /**
 271      * Removes the specified action listener from the <code>Timer</code>.
 272      *
 273      * @param listener the listener to remove
 274      */
 275     public void removeActionListener(ActionListener listener) {
 276         listenerList.remove(ActionListener.class, listener);
 277     }
 278 
 279 
 280     /**
 281      * Returns an array of all the action listeners registered
 282      * on this timer.
 283      *
 284      * @return all of the timer's <code>ActionListener</code>s or an empty
 285      *         array if no action listeners are currently registered
 286      *
 287      * @see #addActionListener
 288      * @see #removeActionListener
 289      *
 290      * @since 1.4
 291      */
 292     public ActionListener[] getActionListeners() {
 293         return (ActionListener[])listenerList.getListeners(
 294                 ActionListener.class);
 295     }
 296 
 297 
 298     /**
 299      * Notifies all listeners that have registered interest for
 300      * notification on this event type.
 301      *
 302      * @param e the action event to fire
 303      * @see EventListenerList
 304      */
 305     protected void fireActionPerformed(ActionEvent e) {
 306         // Guaranteed to return a non-null array
 307         Object[] listeners = listenerList.getListenerList();
 308 
 309         // Process the listeners last to first, notifying
 310         // those that are interested in this event
 311         for (int i=listeners.length-2; i>=0; i-=2) {
 312             if (listeners[i]==ActionListener.class) {
 313                 ((ActionListener)listeners[i+1]).actionPerformed(e);
 314             }
 315         }
 316     }
 317 
 318     /**
 319      * Returns an array of all the objects currently registered as
 320      * <code><em>Foo</em>Listener</code>s
 321      * upon this <code>Timer</code>.
 322      * <code><em>Foo</em>Listener</code>s
 323      * are registered using the <code>add<em>Foo</em>Listener</code> method.
 324      * <p>
 325      * You can specify the <code>listenerType</code> argument
 326      * with a class literal, such as <code><em>Foo</em>Listener.class</code>.
 327      * For example, you can query a <code>Timer</code>
 328      * instance <code>t</code>
 329      * for its action listeners
 330      * with the following code:
 331      *
 332      * <pre>ActionListener[] als = (ActionListener[])(t.getListeners(ActionListener.class));</pre>
 333      *
 334      * If no such listeners exist,
 335      * this method returns an empty array.
 336      *
 337      * @param listenerType  the type of listeners requested;
 338      *          this parameter should specify an interface
 339      *          that descends from <code>java.util.EventListener</code>
 340      * @return an array of all objects registered as
 341      *          <code><em>Foo</em>Listener</code>s
 342      *          on this timer,
 343      *          or an empty array if no such
 344      *          listeners have been added
 345      * @exception ClassCastException if <code>listenerType</code> doesn't
 346      *          specify a class or interface that implements
 347      *          <code>java.util.EventListener</code>
 348      *
 349      * @see #getActionListeners
 350      * @see #addActionListener
 351      * @see #removeActionListener
 352      *
 353      * @since 1.3
 354      */
 355     public <T extends EventListener> T[] getListeners(Class<T> listenerType) {
 356         return listenerList.getListeners(listenerType);
 357     }
 358 
 359     /**
 360      * Returns the timer queue.
 361      */
 362     private TimerQueue timerQueue() {
 363         return TimerQueue.sharedInstance();
 364     }
 365 
 366 
 367     /**
 368      * Enables or disables the timer log. When enabled, a message
 369      * is posted to <code>System.out</code> whenever the timer goes off.
 370      *
 371      * @param flag  <code>true</code> to enable logging
 372      * @see #getLogTimers
 373      */
 374     public static void setLogTimers(boolean flag) {
 375         logTimers = flag;
 376     }
 377 
 378 
 379     /**
 380      * Returns <code>true</code> if logging is enabled.
 381      *
 382      * @return <code>true</code> if logging is enabled; otherwise, false
 383      * @see #setLogTimers
 384      */
 385     public static boolean getLogTimers() {
 386         return logTimers;
 387     }
 388 
 389 
 390     /**
 391      * Sets the <code>Timer</code>'s between-event delay, the number of milliseconds
 392      * between successive action events. This does not affect the initial delay
 393      * property, which can be set by the {@code setInitialDelay} method.
 394      *
 395      * @param delay the delay in milliseconds
 396      * @see #setInitialDelay
 397      */
 398     public void setDelay(int delay) {
 399         if (delay < 0) {
 400             throw new IllegalArgumentException("Invalid delay: " + delay);
 401         }
 402         else {
 403             this.delay = delay;
 404         }
 405     }
 406 
 407 
 408     /**
 409      * Returns the delay, in milliseconds,
 410      * between firings of action events.
 411      *
 412      * @see #setDelay
 413      * @see #getInitialDelay
 414      */
 415     public int getDelay() {
 416         return delay;
 417     }
 418 
 419 
 420     /**
 421      * Sets the <code>Timer</code>'s initial delay, the time
 422      * in milliseconds to wait after the timer is started
 423      * before firing the first event. Upon construction, this
 424      * is set to be the same as the between-event delay,
 425      * but then its value is independent and remains unaffected
 426      * by changes to the between-event delay.
 427      *
 428      * @param initialDelay the initial delay, in milliseconds
 429      * @see #setDelay
 430      */
 431     public void setInitialDelay(int initialDelay) {
 432         if (initialDelay < 0) {
 433             throw new IllegalArgumentException("Invalid initial delay: " +
 434                                                initialDelay);
 435         }
 436         else {
 437             this.initialDelay = initialDelay;
 438         }
 439     }
 440 
 441 
 442     /**
 443      * Returns the <code>Timer</code>'s initial delay.
 444      *
 445      * @see #setInitialDelay
 446      * @see #setDelay
 447      */
 448     public int getInitialDelay() {
 449         return initialDelay;
 450     }
 451 
 452 
 453     /**
 454      * If <code>flag</code> is <code>false</code>,
 455      * instructs the <code>Timer</code> to send only one
 456      * action event to its listeners.
 457      *
 458      * @param flag specify <code>false</code> to make the timer
 459      *             stop after sending its first action event
 460      */
 461     public void setRepeats(boolean flag) {
 462         repeats = flag;
 463     }
 464 
 465 
 466     /**
 467      * Returns <code>true</code> (the default)
 468      * if the <code>Timer</code> will send
 469      * an action event
 470      * to its listeners multiple times.
 471      *
 472      * @see #setRepeats
 473      */
 474     public boolean isRepeats() {
 475         return repeats;
 476     }
 477 
 478 
 479     /**
 480      * Sets whether the <code>Timer</code> coalesces multiple pending
 481      * <code>ActionEvent</code> firings.
 482      * A busy application may not be able
 483      * to keep up with a <code>Timer</code>'s event generation,
 484      * causing multiple
 485      * action events to be queued.  When processed,
 486      * the application sends these events one after the other, causing the
 487      * <code>Timer</code>'s listeners to receive a sequence of
 488      * events with no delay between them. Coalescing avoids this situation
 489      * by reducing multiple pending events to a single event.
 490      * <code>Timer</code>s
 491      * coalesce events by default.
 492      *
 493      * @param flag specify <code>false</code> to turn off coalescing
 494      */
 495     public void setCoalesce(boolean flag) {
 496         boolean old = coalesce;
 497         coalesce = flag;
 498         if (!old && coalesce) {
 499             // We must do this as otherwise if the Timer once notified
 500             // in !coalese mode notify will be stuck to true and never
 501             // become false.
 502             cancelEvent();
 503         }
 504     }
 505 
 506 
 507     /**
 508      * Returns <code>true</code> if the <code>Timer</code> coalesces
 509      * multiple pending action events.
 510      *
 511      * @see #setCoalesce
 512      */
 513     public boolean isCoalesce() {
 514         return coalesce;
 515     }
 516 
 517 
 518     /**
 519      * Sets the string that will be delivered as the action command
 520      * in <code>ActionEvent</code>s fired by this timer.
 521      * <code>null</code> is an acceptable value.
 522      *
 523      * @param command the action command
 524      * @since 1.6
 525      */
 526     public void setActionCommand(String command) {
 527         this.actionCommand = command;
 528     }
 529 
 530 
 531     /**
 532      * Returns the string that will be delivered as the action command
 533      * in <code>ActionEvent</code>s fired by this timer. May be
 534      * <code>null</code>, which is also the default.
 535      *
 536      * @return the action command used in firing events
 537      * @since 1.6
 538      */
 539     public String getActionCommand() {
 540         return actionCommand;
 541     }
 542 
 543 
 544     /**
 545      * Starts the <code>Timer</code>,
 546      * causing it to start sending action events
 547      * to its listeners.
 548      *
 549      * @see #stop
 550      */
 551      public void start() {
 552         timerQueue().addTimer(this, getInitialDelay());
 553     }
 554 
 555 
 556     /**
 557      * Returns <code>true</code> if the <code>Timer</code> is running.
 558      *
 559      * @see #start
 560      */
 561     public boolean isRunning() {
 562         return timerQueue().containsTimer(this);
 563     }
 564 
 565 
 566     /**
 567      * Stops the <code>Timer</code>,
 568      * causing it to stop sending action events
 569      * to its listeners.
 570      *
 571      * @see #start
 572      */
 573     public void stop() {
 574         getLock().lock();
 575         try {
 576             cancelEvent();
 577             timerQueue().removeTimer(this);
 578         } finally {
 579             getLock().unlock();
 580         }
 581     }
 582 
 583 
 584     /**
 585      * Restarts the <code>Timer</code>,
 586      * canceling any pending firings and causing
 587      * it to fire with its initial delay.
 588      */
 589     public void restart() {
 590         getLock().lock();
 591         try {
 592             stop();
 593             start();
 594         } finally {
 595             getLock().unlock();
 596         }
 597     }
 598 
 599 
 600     /**
 601      * Resets the internal state to indicate this Timer shouldn't notify
 602      * any of its listeners. This does not stop a repeatable Timer from
 603      * firing again, use <code>stop</code> for that.
 604      */
 605     void cancelEvent() {
 606         notify.set(false);
 607     }
 608 
 609 
 610     void post() {
 611         if (notify.compareAndSet(false, true) || !coalesce) {
 612             AccessController.doPrivileged(new PrivilegedAction<Void>() {
 613                 public Void run() {
 614                     SwingUtilities.invokeLater(doPostEvent);
 615                     return null;
 616                  }
 617             }, getAccessControlContext());
 618         }
 619     }
 620 
 621     Lock getLock() {
 622         return lock;
 623     }
 624 
 625     /*
 626      * We have to use readResolve because we can not initialize final
 627      * fields for deserialized object otherwise
 628      */
 629     private Object readResolve() {
 630         Timer timer = new Timer(getDelay(), null);
 631         timer.listenerList = listenerList;
 632         timer.initialDelay = initialDelay;
 633         timer.delay = delay;
 634         timer.repeats = repeats;
 635         timer.coalesce = coalesce;
 636         timer.actionCommand = actionCommand;
 637         return timer;
 638     }
 639 
 640      private void readObject(ObjectInputStream in) 
 641         throws ClassNotFoundException, IOException
 642      {
 643         this.acc = AccessController.getContext();
 644         in.defaultReadObject();
 645      }
 646 }