libjava/classpath/java/awt/Button.java

   1 /* Button.java -- AWT button widget
   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.awt;
  40
  41 import java.awt.event.ActionEvent;
  42 import java.awt.event.ActionListener;
  43 import java.awt.peer.ButtonPeer;
  44 import java.lang.reflect.Array;
  45 import java.util.EventListener;
  46
  47 import javax.accessibility.Accessible;
  48 import javax.accessibility.AccessibleAction;
  49 import javax.accessibility.AccessibleContext;
  50 import javax.accessibility.AccessibleRole;
  51 import javax.accessibility.AccessibleValue;
  52
  53 /**
  54   * This class provides a button widget for the AWT.
  55   *
  56   * @author Aaron M. Renn (arenn@urbanophile.com)
  57   * @author Tom Tromey (tromey@cygnus.com)
  58   */
  59 public class Button extends Component
  60   implements java.io.Serializable, Accessible
  61 {
  62
  63 /*
  64  * Static Variables
  65  */
  66
  67 // FIXME: Need readObject/writeObject for serialization
  68
  69 // Serialization version constant
  70 private static final long serialVersionUID = -8774683716313001058L;
  71
  72 /*************************************************************************/
  73
  74 /*
  75  * Instance Variables
  76  */
  77
  78 /**
  79   * @serial The action command name for this button.
  80   * This is package-private to avoid an accessor method.
  81   */
  82 String actionCommand;
  83
  84 /**
  85   * @serial The label for this button.
  86   * This is package-private to avoid an accessor method.
  87   */
  88 String label;
  89
  90 // List of ActionListeners for this class.
  91 private transient ActionListener action_listeners;
  92
  93   /*
  94    * The number used to generate the name returned by getName.
  95    */
  96   private static transient long next_button_number;
  97
  98   protected class AccessibleAWTButton extends AccessibleAWTComponent
  99     implements AccessibleAction, AccessibleValue
 100   {
 101     private static final long serialVersionUID = -5932203980244017102L;
 102
 103     protected AccessibleAWTButton()
 104     {
 105       // Do nothing here.
 106     }
 107
 108     /* (non-Javadoc)
 109      * @see javax.accessibility.AccessibleAction#getAccessibleActionCount()
 110      */
 111     public int getAccessibleActionCount()
 112     {
 113       // Only 1 action possible
 114       return 1;
 115     }
 116
 117     /* (non-Javadoc)
 118      * @see javax.accessibility.AccessibleAction#getAccessibleActionDescription(int)
 119      */
 120     public String getAccessibleActionDescription(int i)
 121     {
 122       // JDK 1.4.2 returns the string "click" for action 0.  However, the API
 123       // docs don't say what the string to be returned is, beyond being a
 124       // description of the action.  So we return the same thing for
 125       // compatibility with 1.4.2.
 126       if (i == 0)
 127         return "click";
 128       return null;
 129     }
 130
 131     /* (non-Javadoc)
 132      * @see javax.accessibility.AccessibleAction#doAccessibleAction(int)
 133      */
 134     public boolean doAccessibleAction(int i)
 135     {
 136       if (i != 0)
 137         return false;
 138       processActionEvent(new ActionEvent(this, ActionEvent.ACTION_PERFORMED, actionCommand));
 139       return true;
 140     }
 141
 142     public String getAccessibleName()
 143     {
 144       return label;
 145     }
 146
 147     public AccessibleAction getAccessibleAction()
 148     {
 149       return this;
 150     }
 151
 152     public AccessibleValue getAccessibleValue()
 153     {
 154       return this;
 155     }
 156
 157     /* (non-Javadoc)
 158      * @see javax.accessibility.AccessibleValue#getCurrentAccessibleValue()
 159      */
 160     public Number getCurrentAccessibleValue()
 161     {
 162       // Docs say return 1 if selected, but buttons can't be selected, right?
 163       return new Integer(0);
 164     }
 165
 166     /* (non-Javadoc)
 167      * @see javax.accessibility.AccessibleValue#setCurrentAccessibleValue(java.lang.Number)
 168      */
 169     public boolean setCurrentAccessibleValue(Number number)
 170     {
 171       // Since there's no selection with buttons, we're ignoring this.
 172       // TODO someone who knows shoulw check this.
 173       return false;
 174     }
 175
 176     /* (non-Javadoc)
 177      * @see javax.accessibility.AccessibleValue#getMinimumAccessibleValue()
 178      */
 179     public Number getMinimumAccessibleValue()
 180     {
 181       return new Integer(0);
 182     }
 183
 184     /* (non-Javadoc)
 185      * @see javax.accessibility.AccessibleValue#getMaximumAccessibleValue()
 186      */
 187     public Number getMaximumAccessibleValue()
 188     {
 189       return new Integer(0);
 190     }
 191
 192     public AccessibleRole getAccessibleRole()
 193     {
 194       return AccessibleRole.PUSH_BUTTON;
 195     }
 196   }
 197
 198 /*************************************************************************/
 199
 200 /*
 201  * Constructors
 202  */
 203
 204 /**
 205   * Initializes a new instance of <code>Button</code> with no label.
 206   *
 207   * @exception HeadlessException If GraphicsEnvironment.isHeadless()
 208   * returns true
 209   */
 210 public
 211 Button()
 212 {
 213   this("");
 214 }
 215
 216 /*************************************************************************/
 217
 218 /**
 219   * Initializes a new instance of <code>Button</code> with the specified
 220   * label.  The action command name is also initialized to this value.
 221   *
 222   * @param label The label to display on the button.
 223   *
 224   * @exception HeadlessException If GraphicsEnvironment.isHeadless()
 225   * returns true
 226   */
 227 public
 228 Button(String label)
 229 {
 230   this.label = label;
 231   actionCommand = label;
 232
 233   if (GraphicsEnvironment.isHeadless ())
 234     throw new HeadlessException ();
 235 }
 236
 237 /*************************************************************************/
 238
 239 /*
 240  * Instance Variables
 241  */
 242
 243 /**
 244   * Returns the label for this button.
 245   *
 246   * @return The label for this button.
 247   */
 248 public String
 249 getLabel()
 250 {
 251   return(label);
 252 }
 253
 254 /*************************************************************************/
 255
 256 /**
 257   * Sets the label for this button to the specified value.
 258   *
 259   * @param label The new label for this button.
 260   */
 261 public synchronized void
 262 setLabel(String label)
 263 {
 264   this.label = label;
 265   actionCommand = label;
 266   if (peer != null)
 267     {
 268       ButtonPeer bp = (ButtonPeer) peer;
 269       bp.setLabel (label);
 270     }
 271 }
 272
 273 /*************************************************************************/
 274
 275 /**
 276   * Returns the action command name for this button.
 277   *
 278   * @return The action command name for this button.
 279   */
 280 public String
 281 getActionCommand()
 282 {
 283   return(actionCommand);
 284 }
 285
 286 /*************************************************************************/
 287
 288 /**
 289   * Sets the action command name for this button to the specified value.
 290   *
 291   * @param actionCommand The new action command name.
 292   */
 293 public void
 294 setActionCommand(String actionCommand)
 295 {
 296   this.actionCommand = actionCommand == null ? label : actionCommand;
 297 }
 298
 299 /*************************************************************************/
 300
 301 /**
 302   * Adds a new entry to the list of listeners that will receive
 303   * action events from this button.
 304   *
 305   * @param listener The listener to add.
 306   */
 307 public synchronized void
 308 addActionListener(ActionListener listener)
 309 {
 310   action_listeners = AWTEventMulticaster.add(action_listeners, listener);
 311 }
 312
 313 /*************************************************************************/
 314
 315 /**
 316   * Removes the specified listener from the list of listeners that will
 317   * receive action events from this button.
 318   *
 319   * @param listener The listener to remove.
 320   */
 321 public synchronized void
 322 removeActionListener(ActionListener listener)
 323 {
 324   action_listeners = AWTEventMulticaster.remove(action_listeners, listener);
 325 }
 326
 327   /**
 328    * Returns all added <code>ActionListener</code> objects.
 329    *
 330    * @return an array of listeners
 331    *
 332    * @since 1.4
 333    */
 334   public synchronized ActionListener[] getActionListeners()
 335   {
 336     return (ActionListener[])
 337       AWTEventMulticaster.getListeners(action_listeners,
 338                                        ActionListener.class);
 339   }
 340
 341 /**
 342  * Returns all registered EventListers of the given listenerType.
 343  * listenerType must be a subclass of EventListener, or a
 344  * ClassClassException is thrown.
 345  *
 346  * @param listenerType the listener type to return
 347  *
 348  * @return an array of listeners
 349  *
 350  * @exception ClassCastException If listenerType doesn't specify a class or
 351  * interface that implements @see java.util.EventListener.
 352  *
 353  * @since 1.3
 354  */
 355   public EventListener[] getListeners(Class listenerType)
 356   {
 357     if (listenerType == ActionListener.class)
 358       return getActionListeners();
 359     return (EventListener[]) Array.newInstance(listenerType, 0);
 360   }
 361
 362 /*************************************************************************/
 363
 364 /**
 365   * Notifies this button that it should create its native peer object.
 366   */
 367 public void
 368 addNotify()
 369 {
 370   if (peer == null)
 371     peer = getToolkit ().createButton (this);
 372   super.addNotify();
 373 }
 374
 375 /*************************************************************************/
 376
 377 /**
 378   * Processes an event for this button.  If the specified event is an
 379   * instance of <code>ActionEvent</code>, then the
 380   * <code>processActionEvent()</code> method is called to dispatch it
 381   * to any registered listeners.  Otherwise, the superclass method
 382   * will be invoked.  Note that this method will not be called at all
 383   * unless <code>ActionEvent</code>'s are enabled.  This will be done
 384   * implicitly if any listeners are added.
 385   *
 386   * @param event The event to process.
 387   */
 388 protected void
 389 processEvent(AWTEvent event)
 390 {
 391   if (event instanceof ActionEvent)
 392     processActionEvent((ActionEvent)event);
 393   else
 394     super.processEvent(event);
 395 }
 396
 397 /*************************************************************************/
 398
 399 /**
 400   * This method dispatches an action event for this button to any
 401   * registered listeners.
 402   *
 403   * @param event The event to process.
 404   */
 405 protected void
 406 processActionEvent(ActionEvent event)
 407 {
 408   if (action_listeners != null)
 409     action_listeners.actionPerformed(event);
 410 }
 411
 412 void
 413 dispatchEventImpl(AWTEvent e)
 414 {
 415   if (e.id <= ActionEvent.ACTION_LAST
 416       && e.id >= ActionEvent.ACTION_FIRST
 417       && (action_listeners != null
 418           || (eventMask & AWTEvent.ACTION_EVENT_MASK) != 0))
 419     processEvent(e);
 420   else
 421     super.dispatchEventImpl(e);
 422 }
 423
 424 /*************************************************************************/
 425
 426 /**
 427   * Returns a debugging string for this button.
 428   *
 429   * @return A debugging string for this button.
 430   */
 431 protected String
 432 paramString()
 433 {
 434   return getName () + "," + getX () + "," + getY () + ","
 435     + getWidth () + "x" + getHeight () + ",label=" + getLabel ();
 436 }
 437
 438 /**
 439  * Gets the AccessibleContext associated with this <code>Button</code>.
 440  * The context is created, if necessary.
 441  *
 442  * @return the associated context
 443  */
 444 public AccessibleContext getAccessibleContext()
 445 {
 446   /* Create the context if this is the first request */
 447   if (accessibleContext == null)
 448     accessibleContext = new AccessibleAWTButton();
 449   return accessibleContext;
 450 }
 451
 452   /**
 453    * Generate a unique name for this button.
 454    *
 455    * @return A unique name for this button.
 456    */
 457   String generateName ()
 458   {
 459     return "button" + getUniqueLong ();
 460   }
 461
 462   private static synchronized long getUniqueLong ()
 463   {
 464     return next_button_number++;
 465   }
 466
 467 } // class Button
 468