libjava/java/awt/CheckboxMenuItem.java

   1 /* CheckboxMenuItem.java -- A menu option with a checkbox on it.
   2    Copyright (C) 1999, 2000, 2001, 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., 59 Temple Place, Suite 330, Boston, MA
  19 02111-1307 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.ItemEvent;
  42 import java.awt.event.ItemListener;
  43 import java.awt.peer.CheckboxMenuItemPeer;
  44 import java.util.EventListener;
  45
  46 import javax.accessibility.Accessible;
  47 import javax.accessibility.AccessibleAction;
  48 import javax.accessibility.AccessibleContext;
  49 import javax.accessibility.AccessibleValue;
  50
  51 /**
  52   * This class implements a menu item that has a checkbox on it indicating
  53   * the selected state of some option.
  54   *
  55   * @author Aaron M. Renn (arenn@urbanophile.com)
  56   * @author Tom Tromey (tromey@redhat.com)
  57   */
  58 public class CheckboxMenuItem extends MenuItem
  59   implements ItemSelectable, Accessible
  60 {
  61
  62 /*
  63  * Static Variables
  64  */
  65
  66 // Serialization constant
  67 private static final long serialVersionUID = 6190621106981774043L;
  68
  69 /*
  70  * Instance Variables
  71  */
  72
  73 /**
  74   * @serial The state of the checkbox, with <code>true</code> being on and
  75   * <code>false</code> being off.
  76   */
  77 private boolean state;
  78
  79 // List of registered ItemListeners
  80 private transient ItemListener item_listeners;
  81
  82 /*************************************************************************/
  83
  84 /*
  85  * Constructors
  86  */
  87
  88 /**
  89   * Initializes a new instance of <code>CheckboxMenuItem</code> with no
  90   * label and an initial state of off.
  91   *
  92   * @exception HeadlessException If GraphicsEnvironment.isHeadless()
  93   * returns true.
  94   */
  95 public
  96 CheckboxMenuItem()
  97 {
  98   this("", false);
  99 }
 100
 101 /*************************************************************************/
 102
 103 /**
 104   * Initializes a new instance of <code>CheckboxMenuItem</code> with the
 105   * specified label and an initial state of off.
 106   *
 107   * @param label The label of the menu item.
 108   *
 109   * @exception HeadlessException If GraphicsEnvironment.isHeadless()
 110   * returns true.
 111   */
 112 public
 113 CheckboxMenuItem(String label)
 114 {
 115   this(label, false);
 116 }
 117
 118 /*************************************************************************/
 119
 120 /**
 121   * Initializes a new instance of <code>CheckboxMenuItem</code> with the
 122   * specified label and initial state.
 123   *
 124   * @param label The label of the menu item.
 125   * @param state The initial state of the menu item, where <code>true</code>
 126   * is on, and <code>false</code> is off.
 127   *
 128   * @exception HeadlessException If GraphicsEnvironment.isHeadless()
 129   * returns true.
 130   */
 131 public
 132 CheckboxMenuItem(String label, boolean state)
 133 {
 134   super(label);
 135   this.state = state;
 136
 137   if (GraphicsEnvironment.isHeadless())
 138     throw new HeadlessException ();
 139 }
 140
 141 /*************************************************************************/
 142
 143 /*
 144  * Instance Methods
 145  */
 146
 147 /**
 148   * Returns the state of this menu item.
 149   *
 150   * @return The state of this menu item.
 151   */
 152 public boolean
 153 getState()
 154 {
 155   return(state);
 156 }
 157
 158 /*************************************************************************/
 159
 160 /**
 161   * Sets the state of this menu item.
 162   *
 163   * @param state The initial state of the menu item, where <code>true</code>
 164   * is on, and <code>false</code> is off.
 165   */
 166 public synchronized void
 167 setState(boolean state)
 168 {
 169   this.state = state;
 170   if (peer != null)
 171     {
 172       CheckboxMenuItemPeer cp = (CheckboxMenuItemPeer) peer;
 173       cp.setState (state);
 174     }
 175 }
 176
 177 /*************************************************************************/
 178
 179 /**
 180   * Returns an array of length 1 with the menu item label for this object
 181   * if the state is on.  Otherwise <code>null</code> is returned.
 182   *
 183   * @return An array with this menu item's label if it has a state of on,
 184   * or <code>null</code> otherwise.
 185   */
 186 public Object[]
 187 getSelectedObjects()
 188 {
 189   if (state == false)
 190     return(null);
 191
 192   Object[] obj = new Object[1];
 193   obj[0] = getLabel();
 194
 195   return(obj);
 196 }
 197
 198 /*************************************************************************/
 199
 200 /**
 201   * Create's this object's native peer
 202   */
 203 public synchronized void
 204 addNotify()
 205 {
 206   if (peer == null)
 207     peer = getToolkit().createCheckboxMenuItem(this);
 208
 209   super.addNotify ();
 210 }
 211
 212 /*************************************************************************/
 213
 214 /**
 215   * Adds the specified listener to the list of registered item listeners
 216   * for this object.
 217   *
 218   * @param listener The listener to add.
 219   */
 220 public synchronized void
 221 addItemListener(ItemListener listener)
 222 {
 223   item_listeners = AWTEventMulticaster.add(item_listeners, listener);
 224
 225   enableEvents(AWTEvent.ITEM_EVENT_MASK);
 226 }
 227
 228 /*************************************************************************/
 229
 230 /**
 231   * Removes the specified listener from the list of registered item
 232   * listeners for this object.
 233   *
 234   * @param listener The listener to remove.
 235   */
 236 public synchronized void
 237 removeItemListener(ItemListener listener)
 238 {
 239   item_listeners = AWTEventMulticaster.remove(item_listeners, listener);
 240 }
 241
 242 /*************************************************************************/
 243
 244 /**
 245   * Processes the specified event by calling <code>processItemEvent()</code>
 246   * if it is an instance of <code>ItemEvent</code> or calling the superclass
 247   * method otherwise.
 248   *
 249   * @param event The event to process.
 250   */
 251 protected void
 252 processEvent(AWTEvent event)
 253 {
 254   if (event instanceof ItemEvent)
 255     processItemEvent((ItemEvent)event);
 256   else
 257     super.processEvent(event);
 258 }
 259
 260 /*************************************************************************/
 261
 262 /**
 263   * Processes the specified event by dispatching it to any registered listeners.
 264   *
 265   * @param event The event to process.
 266   */
 267 protected void
 268 processItemEvent(ItemEvent event)
 269 {
 270   if (item_listeners != null)
 271     item_listeners.itemStateChanged(event);
 272 }
 273
 274 void
 275 dispatchEventImpl(AWTEvent e)
 276 {
 277   if (e instanceof ItemEvent)
 278     {
 279       synchronized (this)
 280         {
 281           state = (((ItemEvent) e).getStateChange() == ItemEvent.SELECTED);
 282         }
 283     }
 284
 285   if (e.id <= ItemEvent.ITEM_LAST
 286       && e.id >= ItemEvent.ITEM_FIRST
 287       && (item_listeners != null
 288           || (eventMask & AWTEvent.ITEM_EVENT_MASK) != 0))
 289     processEvent(e);
 290   else
 291     super.dispatchEventImpl(e);
 292 }
 293
 294 /*************************************************************************/
 295
 296 /**
 297   * Returns a debugging string for this object.
 298   *
 299   * @return A debugging string for this object.
 300   */
 301 public String
 302 paramString()
 303 {
 304   return ("label=" + getLabel() + ",state=" + state
 305           + "," + super.paramString());
 306 }
 307
 308   /**
 309    * Returns an array of all the objects currently registered as FooListeners
 310    * upon this <code>CheckboxMenuItem</code>. FooListeners are registered using
 311    * the addFooListener method.
 312    *
 313    * @exception ClassCastException If listenerType doesn't specify a class or
 314    * interface that implements java.util.EventListener.
 315    */
 316   public EventListener[] getListeners (Class listenerType)
 317   {
 318     if (listenerType == ItemListener.class)
 319       return AWTEventMulticaster.getListeners (item_listeners, listenerType);
 320
 321     return super.getListeners (listenerType);
 322   }
 323
 324   /**
 325    * Returns an aray of all item listeners currently registered to this
 326    * <code>CheckBoxMenuItem</code>.
 327    */
 328   public ItemListener[] getItemListeners ()
 329   {
 330     return (ItemListener[]) getListeners (ItemListener.class);
 331   }
 332
 333
 334   protected class AccessibleAWTCheckboxMenuItem extends AccessibleAWTMenuItem
 335     implements AccessibleAction, AccessibleValue
 336   {
 337     // I think the base class provides the necessary implementation
 338   }
 339
 340   /**
 341    * Gets the AccessibleContext associated with this <code>CheckboxMenuItem</code>.
 342    * The context is created, if necessary.
 343    *
 344    * @return the associated context
 345    */
 346   public AccessibleContext getAccessibleContext()
 347   {
 348     /* Create the context if this is the first request */
 349     if (accessibleContext == null)
 350       accessibleContext = new AccessibleAWTCheckboxMenuItem();
 351     return accessibleContext;
 352   }
 353
 354 } // class CheckboxMenuItem
 355