libjava/classpath/java/applet/Applet.java

   1 /* Applet.java -- Java base applet class
   2    Copyright (C) 1999, 2002, 2004, 2005  Free Software Foundation, Inc.
   3
   4 This file is part of GNU Classpath.
   5
   6 GNU Classpath is free software; you can redistribute it and/or modify
   7 it under the terms of the GNU General Public License as published by
   8 the Free Software Foundation; either version 2, or (at your option)
   9 any later version.
  10
  11 GNU Classpath is distributed in the hope that it will be useful, but
  12 WITHOUT ANY WARRANTY; without even the implied warranty of
  13 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  14 General Public License for more details.
  15
  16 You should have received a copy of the GNU General Public License
  17 along with GNU Classpath; see the file COPYING.  If not, write to the
  18 Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
  19 02110-1301 USA.
  20
  21 Linking this library statically or dynamically with other modules is
  22 making a combined work based on this library.  Thus, the terms and
  23 conditions of the GNU General Public License cover the whole
  24 combination.
  25
  26 As a special exception, the copyright holders of this library give you
  27 permission to link this library with independent modules to produce an
  28 executable, regardless of the license terms of these independent
  29 modules, and to copy and distribute the resulting executable under
  30 terms of your choice, provided that you also meet, for each linked
  31 independent module, the terms and conditions of the license of that
  32 module.  An independent module is a module which is not derived from
  33 or based on this library.  If you modify this library, you may extend
  34 this exception to your version of the library, but you are not
  35 obligated to do so.  If you do not wish to do so, delete this
  36 exception statement from your version. */
  37
  38
  39 package java.applet;
  40
  41 import java.awt.Component;
  42 import java.awt.Dimension;
  43 import java.awt.GraphicsEnvironment;
  44 import java.awt.HeadlessException;
  45 import java.awt.Image;
  46 import java.awt.Panel;
  47 import java.io.IOException;
  48 import java.io.ObjectInputStream;
  49 import java.net.MalformedURLException;
  50 import java.net.URL;
  51 import java.util.Locale;
  52
  53 import javax.accessibility.AccessibleContext;
  54 import javax.accessibility.AccessibleRole;
  55 import javax.accessibility.AccessibleState;
  56 import javax.accessibility.AccessibleStateSet;
  57 import javax.sound.sampled.AudioSystem;
  58 import javax.sound.sampled.Clip;
  59 import javax.sound.sampled.LineUnavailableException;
  60 import javax.sound.sampled.UnsupportedAudioFileException;
  61
  62 /**
  63  * This is the base applet class.  An applet is a Java program that
  64  * runs inside a web browser or other applet viewer in a restricted
  65  * environment.
  66  *
  67  * <p>To be useful, a subclass should override at least start(). Also useful
  68  * are init, stop, and destroy for control purposes, and getAppletInfo and
  69  * getParameterInfo for descriptive purposes.
  70  *
  71  * @author Aaron M. Renn (arenn@urbanophile.com)
  72  * @author Eric Blake (ebb9@email.byu.edu)
  73  * @since 1.0
  74  * @status updated to 1.4
  75  */
  76 public class Applet extends Panel
  77 {
  78   /**
  79    * Compatible with JDK 1.0+.
  80    */
  81   private static final long serialVersionUID = -5836846270535785031L;
  82
  83   /** The applet stub for this applet. */
  84   private transient AppletStub stub;
  85
  86   /** Some applets call setSize in their constructors.  In that case,
  87       these fields are used to store width and height values until a
  88       stub is set. */
  89   private transient int width;
  90   private transient int height;
  91
  92   /**
  93    * The accessibility context for this applet.
  94    *
  95    * @serial the accessibleContext for this
  96    * @since 1.2
  97    */
  98   private AccessibleContext accessibleContext;
  99
 100   /**
 101    * Default constructor for subclasses.
 102    *
 103    * @throws HeadlessException if in a headless environment
 104    */
 105   public Applet()
 106   {
 107     if (GraphicsEnvironment.isHeadless())
 108       throw new HeadlessException();
 109   }
 110
 111   /**
 112    * The browser calls this method to set the applet's stub, which is the
 113    * low level interface to the browser. Manually setting this to null is
 114    * asking for problems down the road.
 115    *
 116    * @param stub the applet stub for this applet
 117    */
 118   public final void setStub(AppletStub stub)
 119   {
 120     this.stub = stub;
 121
 122     if (width != 0 && height != 0)
 123       stub.appletResize (width, height);
 124   }
 125
 126   /**
 127    * Tests whether or not this applet is currently active. An applet is active
 128    * just before the browser invokes start(), and becomes inactive just
 129    * before the browser invokes stop().
 130    *
 131    * @return <code>true</code> if this applet is active
 132    */
 133   public boolean isActive()
 134   {
 135     return stub.isActive();
 136   }
 137
 138   /**
 139    * Returns the basename URL of the document this applet is embedded in. This
 140    * is everything up to the final '/'.
 141    *
 142    * @return the URL of the document this applet is embedded in
 143    * @see #getCodeBase()
 144    */
 145   public URL getDocumentBase()
 146   {
 147     return stub.getDocumentBase();
 148   }
 149
 150   /**
 151    * Returns the URL of the code base for this applet.
 152    *
 153    * @return the URL of the code base for this applet
 154    */
 155   public URL getCodeBase()
 156   {
 157     return stub.getCodeBase();
 158   }
 159
 160   /**
 161    * Returns the value of the specified parameter that was specified in
 162    * the <code>&lt;APPLET&gt;</code> tag for this applet.
 163    *
 164    * @param name the parameter name
 165    * @return the parameter value, or null if the parameter does not exist
 166    * @throws NullPointerException if name is null
 167    */
 168   public String getParameter(String name)
 169   {
 170     return stub.getParameter(name);
 171   }
 172
 173   /**
 174    * Returns the applet context for this applet.
 175    *
 176    * @return the applet context for this applet
 177    */
 178   public AppletContext getAppletContext()
 179   {
 180     return stub.getAppletContext();
 181   }
 182
 183   /**
 184    * Requests that the applet window for this applet be resized.
 185    *
 186    * @param width the new width in pixels
 187    * @param height the new height in pixels
 188    */
 189   public void resize(int width, int height)
 190   {
 191     if (stub == null)
 192       {
 193         this.width = width;
 194         this.height = height;
 195       }
 196     else
 197       stub.appletResize(width, height);
 198   }
 199
 200   /**
 201    * Requests that the applet window for this applet be resized.
 202    *
 203    * @param dim the requested dimensions
 204    * @throws NullPointerException if dim is null
 205    */
 206   public void resize(Dimension dim)
 207   {
 208     resize(dim.width, dim.height);
 209   }
 210
 211   /**
 212    * Displays the specified message in the status window if that window
 213    * exists.
 214    *
 215    * @param message the status message, may be null
 216    */
 217   public void showStatus(String message)
 218   {
 219     getAppletContext().showStatus(message);
 220   }
 221
 222   /**
 223    * Returns an image from the specified URL.  Note that the image is not
 224    * actually retrieved until the applet attempts to display it, so this
 225    * method returns immediately.
 226    *
 227    * @param url the URL of the image
 228    * @return the retrieved image
 229    * @throws NullPointerException if url is null
 230    */
 231   public Image getImage(URL url)
 232   {
 233     return getAppletContext().getImage(url);
 234   }
 235
 236   /**
 237    * Returns an image from the specified absolute URL, and relative path
 238    * from that URL.  Note that the image is not actually retrieved until the
 239    * applet attempts to display it, so this method returns immediately.
 240    * This calls <code>getImage(new URL(url, name))</code>, but if building
 241    * the new URL fails, this returns null.
 242    *
 243    * @param url the base URL of the image
 244    * @param name the name of the image relative to the URL
 245    * @return the retrieved image, or null on failure
 246    * @see #getImage(URL)
 247    */
 248   public Image getImage(URL url, String name)
 249   {
 250     try
 251       {
 252         return getImage(new URL(url, name));
 253       }
 254     catch (MalformedURLException e)
 255       {
 256         return null;
 257       }
 258   }
 259
 260   /**
 261    * Returns an audio clip from the specified URL. This clip is not tied to
 262    * any particular applet.
 263    *
 264    * @param url the URL of the audio clip
 265    * @return the retrieved audio clip
 266    * @throws NullPointerException if url is null
 267    * @see #getAudioClip(URL)
 268    * @since 1.2
 269    */
 270   public static final AudioClip newAudioClip(URL url)
 271   {
 272     return new URLAudioClip(url);
 273   }
 274
 275   /**
 276    * Returns an audio clip from the specified URL. Note that the clip is not
 277    * actually retrieved until the applet attempts to play it, so this method
 278    * returns immediately.
 279    *
 280    * @param url the URL of the audio clip
 281    * @return the retrieved audio clip
 282    * @throws NullPointerException if url is null
 283    */
 284   public AudioClip getAudioClip(URL url)
 285   {
 286     return getAppletContext().getAudioClip(url);
 287   }
 288
 289   /**
 290    * Returns an audio clip from the specified absolute URL, and relative path
 291    * from that URL.  Note that the clip is not actually retrieved until the
 292    * applet attempts to play it, so this method returns immediately. This
 293    * calls <code>getAudioClip(new URL(url, name))</code>, but if building
 294    * the new URL fails, this returns null.
 295    *
 296    * @param url the base URL of the audio clip
 297    * @param name the name of the clip relative to the URL
 298    * @return the retrieved audio clip, or null on failure
 299    * @see #getAudioClip(URL)
 300    */
 301   public AudioClip getAudioClip(URL url, String name)
 302   {
 303     try
 304       {
 305         return getAudioClip(new URL(url, name));
 306       }
 307     catch (MalformedURLException e)
 308       {
 309         return null;
 310       }
 311   }
 312
 313   /**
 314    * Returns a descriptive string with applet defined information.  The
 315    * implementation in this class returns <code>null</code>, so subclasses
 316    * must override to return information.
 317    *
 318    * @return a string describing the author, version, and applet copyright
 319    */
 320   public String getAppletInfo()
 321   {
 322     return null;
 323   }
 324
 325   /**
 326    * Returns the locale for this applet, if it has been set.  If no applet
 327    * specific locale has been set, the default locale is returned.
 328    *
 329    * @return the locale for this applet
 330    * @see Component#setLocale(Locale)
 331    * @since 1.1
 332    */
 333   public Locale getLocale()
 334   {
 335     return super.getLocale();
 336   }
 337
 338   /**
 339    * Returns a list of parameters this applet supports.  Each element of
 340    * the outer array is an array of three strings with the name of the
 341    * parameter, the data type or valid values, and a description.  This
 342    * method is optional and the default implementation returns null.
 343    *
 344    * @return the list of parameters supported by this applet
 345    */
 346   public String[][] getParameterInfo()
 347   {
 348     return null;
 349   }
 350
 351   /**
 352    * Loads and plays the audio clip pointed to by the specified URL. This does
 353    * nothing if the URL does not point to a valid audio clip.
 354    *
 355    * @param url the URL of the audio clip
 356    * @throws NullPointerException if url is null
 357    * @see #getAudioClip(URL)
 358    */
 359   public void play(URL url)
 360   {
 361     AudioClip ac = getAudioClip(url);
 362     try
 363       {
 364         ac.play();
 365       }
 366     catch (Exception ignored)
 367       {
 368       }
 369   }
 370
 371   /**
 372    * Loads and plays the audio clip pointed to by the specified absolute URL,
 373    * and relative path from that URL. This does nothing if the URL cannot be
 374    * constructed, or if it does not point to a valid audio clip.
 375    *
 376    * @param url the base URL of the audio clip
 377    * @param name the name of the audio clip relative to the URL
 378    * @see #getAudioClip(URL, String)
 379    * @see #play(URL)
 380    */
 381   public void play(URL url, String name)
 382   {
 383     try
 384       {
 385         getAudioClip(url, name).play();
 386       }
 387     catch (Exception ignored)
 388       {
 389       }
 390   }
 391
 392   /**
 393    * This method is called when the applet is first loaded, before start().
 394    * The default implementation does nothing; override to do any one-time
 395    * initialization.
 396    *
 397    * @see #start()
 398    * @see #stop()
 399    * @see #destroy()
 400    */
 401   public void init()
 402   {
 403   }
 404
 405   /**
 406    * This method is called when the applet should start running.  This is
 407    * normally each time a web page containing it is loaded.  The default
 408    * implemention does nothing; override for your applet to be useful.
 409    *
 410    * @see #init()
 411    * @see #stop()
 412    * @see #destroy()
 413    */
 414   public void start()
 415   {
 416   }
 417
 418   /**
 419    * This method is called when the applet should stop running.  This is
 420    * normally when the next web page is loaded.  The default implementation
 421    * does nothing; override for your applet to stop using resources when
 422    * it is no longer visible, but may be restarted soon.
 423    *
 424    * @see #init()
 425    * @see #start()
 426    * @see #destroy()
 427    */
 428   public void stop()
 429   {
 430   }
 431
 432   /**
 433    * This method is called when the applet is being unloaded.  The default
 434    * implementation does nothing; override for your applet to clean up
 435    * resources on exit.
 436    *
 437    * @see #init()
 438    * @see #start()
 439    * @see #stop()
 440    */
 441   public void destroy()
 442   {
 443   }
 444
 445   /**
 446    * Gets the AccessibleContext associated with this applet, creating one if
 447    * necessary. This always returns an instance of {@link AccessibleApplet}.
 448    *
 449    * @return the accessibility context of this applet
 450    * @since 1.3
 451    */
 452   public AccessibleContext getAccessibleContext()
 453   {
 454     if (accessibleContext == null)
 455       accessibleContext = new AccessibleApplet();
 456     return accessibleContext;
 457   }
 458
 459   /**
 460    * Read an applet from an object stream. This checks for a headless
 461    * environment, then does the normal read.
 462    *
 463    * @param s the stream to read from
 464    * @throws ClassNotFoundException if a class is not found
 465    * @throws IOException if deserialization fails
 466    * @throws HeadlessException if this is a headless environment
 467    * @see GraphicsEnvironment#isHeadless()
 468    * @since 1.4
 469    */
 470   private void readObject(ObjectInputStream s)
 471     throws ClassNotFoundException, IOException
 472   {
 473     if (GraphicsEnvironment.isHeadless())
 474       throw new HeadlessException();
 475     s.defaultReadObject();
 476   }
 477
 478   /**
 479    * This class provides accessibility support for Applets, and is the
 480    * runtime type returned by {@link #getAccessibleContext()}.
 481    *
 482    * @author Eric Blake (ebb9@email.byu.edu)
 483    * @since 1.3
 484    */
 485   protected class AccessibleApplet extends AccessibleAWTPanel
 486   {
 487     /**
 488      * Compatible with JDK 1.4+.
 489      */
 490     private static final long serialVersionUID = 8127374778187708896L;
 491
 492     /**
 493      * The default constructor.
 494      */
 495     protected AccessibleApplet()
 496     {
 497     }
 498
 499     /**
 500      * Get the role of this accessible object, a frame.
 501      *
 502      * @return the role of the object
 503      * @see AccessibleRole#FRAME
 504      */
 505     public AccessibleRole getAccessibleRole()
 506     {
 507       return AccessibleRole.FRAME;
 508     }
 509
 510     /**
 511      * Get the state set of this accessible object. In addition to the default
 512      * states of a Component, the applet can also be active.
 513      *
 514      * @return the role of the object
 515      * @see AccessibleState
 516      */
 517     public AccessibleStateSet getAccessibleStateSet()
 518     {
 519       AccessibleStateSet s = super.getAccessibleStateSet();
 520       if (isActive())
 521         s.add(AccessibleState.ACTIVE);
 522       return s;
 523     }
 524   } // class AccessibleApplet
 525
 526   private static class URLAudioClip implements AudioClip
 527   {
 528     // The URL we will try to play.
 529     // This is null if we have already tried to create an
 530     // audio input stream from this URL.
 531     private URL url;
 532
 533     // The real audio clip.  This is null before the URL is read,
 534     // and might be null afterward if we were unable to read the URL
 535     // for some reason.
 536     private Clip clip;
 537
 538     public URLAudioClip(URL url)
 539     {
 540       this.url = url;
 541     }
 542
 543     private synchronized Clip getClip()
 544     {
 545       if (url == null)
 546         return clip;
 547       try
 548         {
 549           clip = AudioSystem.getClip();
 550           clip.open(AudioSystem.getAudioInputStream(url));
 551         }
 552       catch (LineUnavailableException _)
 553         {
 554           // Ignore.
 555         }
 556       catch (IOException _)
 557         {
 558           // Ignore.
 559         }
 560       catch (UnsupportedAudioFileException _)
 561         {
 562           // Ignore.
 563         }
 564       url = null;
 565       return clip;
 566     }
 567
 568     public void loop()
 569     {
 570       Clip myclip = getClip();
 571       if (myclip != null)
 572         myclip.loop(Clip.LOOP_CONTINUOUSLY);
 573     }
 574
 575     public void play()
 576     {
 577       Clip myclip = getClip();
 578       if (myclip != null)
 579         myclip.start();
 580     }
 581
 582     public void stop()
 583     {
 584       Clip myclip = getClip();
 585       if (myclip != null)
 586         {
 587           myclip.stop();
 588           myclip.setFramePosition(0);
 589         }
 590     }
 591   }
 592 } // class Applet