001/* EventListenerList.java -- 002 Copyright (C) 2002, 2004, 2005, 2006, Free Software Foundation, Inc. 003 004This file is part of GNU Classpath. 005 006GNU Classpath is free software; you can redistribute it and/or modify 007it under the terms of the GNU General Public License as published by 008the Free Software Foundation; either version 2, or (at your option) 009any later version. 010 011GNU Classpath is distributed in the hope that it will be useful, but 012WITHOUT ANY WARRANTY; without even the implied warranty of 013MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU 014General Public License for more details. 015 016You should have received a copy of the GNU General Public License 017along with GNU Classpath; see the file COPYING. If not, write to the 018Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 01902110-1301 USA. 020 021Linking this library statically or dynamically with other modules is 022making a combined work based on this library. Thus, the terms and 023conditions of the GNU General Public License cover the whole 024combination. 025 026As a special exception, the copyright holders of this library give you 027permission to link this library with independent modules to produce an 028executable, regardless of the license terms of these independent 029modules, and to copy and distribute the resulting executable under 030terms of your choice, provided that you also meet, for each linked 031independent module, the terms and conditions of the license of that 032module. An independent module is a module which is not derived from 033or based on this library. If you modify this library, you may extend 034this exception to your version of the library, but you are not 035obligated to do so. If you do not wish to do so, delete this 036exception statement from your version. */ 037 038package javax.swing.event; 039 040import gnu.java.lang.CPStringBuilder; 041 042import java.io.IOException; 043import java.io.ObjectInputStream; 044import java.io.ObjectOutputStream; 045import java.io.Serializable; 046import java.lang.reflect.Array; 047import java.util.EventListener; 048 049 050/** 051 * A utility class for keeping track of {@link EventListener}s. 052 * 053 * <p><b>Example for using this class:</b> 054 * 055 * <blockquote><pre> import java.util.EventListener; 056 * import javax.swing.event.EventListenerList; 057 * 058 * class Foo 059 * { 060 * protected final EventListenerList listeners = new EventListenerList(); 061 * protected BarClosedEvent barClosedEvent = null; 062 * 063 * public void addBarListener(BarListener l) 064 * { 065 * listeners.<a href="#add(java.lang.Class, java.util.EventListener)" 066 * >add</a>(BarListener.class, l); 067 * } 068 * 069 * public void removeBarListener(BarListener l) 070 * { 071 * listeners.<a href="#remove(java.lang.Class, java.util.EventListener)" 072 * >remove</a>(BarListener.class, l); 073 * } 074 * 075 * protected void fireBarClosedEvent() 076 * { 077 * Object[] l = listeners.<a href="#getListenerList()" 078 * >getListenerList()</a>; 079 * 080 * for (int i = l.length - 2; i >= 0; i -= 2) 081 * if (l[i] == BarListener.class) 082 * { 083 * // Create the event on demand, when it is needed the first time. 084 * if (barClosedEvent == null) 085 * barClosedEvent = new BarClosedEvent(this); 086 * 087 * ((BarClosedListener) l[i + 1]).barClosed(barClosedEvent); 088 * } 089 * } 090 * }</pre></blockquote> 091 * 092 * @author Andrew Selkirk (aselkirk@sympatico.ca) 093 * @author Sascha Brawer (brawer@dandelis.ch) 094 */ 095public class EventListenerList 096 implements Serializable 097{ 098 /** 099 * An ID for serializing instances of this class; verified with the 100 * serialver tool of Sun J2SE 1.4.1_01. 101 */ 102 static final long serialVersionUID = -5677132037850737084L; 103 104 105 /** 106 * An empty array that is shared by all instances of this class that 107 * have no listeners. 108 */ 109 private static final Object[] NO_LISTENERS = new Object[0]; 110 111 112 /** 113 * An array with all currently registered listeners. The array has 114 * twice as many elements as there are listeners. For an even 115 * integer <code>i</code>, <code>listenerList[i]</code> indicates 116 * the registered class, and <code>listenerList[i + 1]</code> is the 117 * listener. 118 */ 119 protected transient Object[] listenerList = NO_LISTENERS; 120 121 122 /** 123 * EventListenerList constructor 124 */ 125 public EventListenerList() 126 { 127 // Nothing to do here. 128 } 129 130 131 /** 132 * Registers a listener of a specific type. 133 * 134 * @param t the type of the listener. 135 * 136 * @param listener the listener to add, which must be an instance of 137 * <code>t</code>, or of a subclass of <code>t</code>. 138 * 139 * @throws IllegalArgumentException if <code>listener</code> is not 140 * an instance of <code>t</code> (or a subclass thereof). 141 * 142 * @throws NullPointerException if <code>t</code> is <code>null</code>. 143 */ 144 public <T extends EventListener> void add(Class<T> t, T listener) 145 { 146 int oldLength; 147 Object[] newList; 148 149 if (listener == null) 150 return; 151 152 if (!t.isInstance(listener)) 153 throw new IllegalArgumentException(); 154 155 oldLength = listenerList.length; 156 newList = new Object[oldLength + 2]; 157 if (oldLength > 0) 158 System.arraycopy(listenerList, 0, newList, 0, oldLength); 159 160 newList[oldLength] = t; 161 newList[oldLength + 1] = listener; 162 listenerList = newList; 163 } 164 165 166 /** 167 * Determines the number of listeners. 168 */ 169 public int getListenerCount() 170 { 171 return listenerList.length / 2; 172 } 173 174 175 /** 176 * Determines the number of listeners of a particular class. 177 * 178 * @param t the type of listeners to be counted. In order to get 179 * counted, a subscribed listener must be exactly of class 180 * <code>t</code>. Thus, subclasses of <code>t</code> will not be 181 * counted. 182 */ 183 public int getListenerCount(Class<?> t) 184 { 185 int result = 0; 186 for (int i = 0; i < listenerList.length; i += 2) 187 if (t == listenerList[i]) 188 ++result; 189 190 return result; 191 } 192 193 194 /** 195 * Returns an array containing a sequence of listenerType/listener pairs, one 196 * for each listener. 197 * 198 * @return An array containing the listener types and references. 199 */ 200 public Object[] getListenerList() 201 { 202 // returning the internal storage is a bad idea, but tests show that the 203 // reference implementation does this... 204 return listenerList; 205 } 206 207 208 /** 209 * Retrieves the currently subscribed listeners of a particular 210 * type. For a listener to be returned, it must have been 211 * registered with exactly the type <code>c</code>; subclasses are 212 * not considered equal. 213 * 214 * <p>The returned array can always be cast to <code>c[]</code>. 215 * Since it is a newly allocated copy, the caller may arbitrarily 216 * modify the array. 217 * 218 * @param c the class which was passed to {@link #add}. 219 * 220 * @throws ClassCastException if <code>c</code> does not implement 221 * the {@link EventListener} interface. 222 * 223 * @throws NullPointerException if <code>c</code> is 224 * <code>null</code>. 225 * 226 * @return an array of <code>c</code> whose elements are the 227 * currently subscribed listeners of the specified type. If there 228 * are no such listeners, an empty array is returned. 229 * 230 * @since 1.3 231 */ 232 public <T extends EventListener> T[] getListeners(Class<T> c) 233 { 234 int count, f; 235 EventListener[] result; 236 237 count = getListenerCount(c); 238 result = (EventListener[]) Array.newInstance(c, count); 239 f = 0; 240 for (int i = listenerList.length - 2; i >= 0; i -= 2) 241 if (listenerList[i] == c) 242 result[f++] = (EventListener) listenerList[i + 1]; 243 244 return (T[]) result; 245 } 246 247 248 /** 249 * Removes a listener of a specific type. 250 * 251 * @param t the type of the listener. 252 * 253 * @param listener the listener to remove, which must be an instance 254 * of <code>t</code>, or of a subclass of <code>t</code>. 255 * 256 * @throws IllegalArgumentException if <code>listener</code> is not 257 * an instance of <code>t</code> (or a subclass thereof). 258 * 259 * @throws NullPointerException if <code>t</code> is <code>null</code>. 260 */ 261 public <T extends EventListener> void remove(Class<T> t, T listener) 262 { 263 Object[] oldList, newList; 264 int oldLength; 265 266 if (listener == null) 267 return; 268 269 if (!t.isInstance(listener)) 270 throw new IllegalArgumentException(); 271 272 oldList = listenerList; 273 oldLength = oldList.length; 274 for (int i = 0; i < oldLength; i += 2) 275 if (oldList[i] == t && oldList[i + 1] == listener) 276 { 277 if (oldLength == 2) 278 newList = NO_LISTENERS; 279 else 280 { 281 newList = new Object[oldLength - 2]; 282 if (i > 0) 283 System.arraycopy(oldList, 0, newList, 0, i); 284 if (i < oldLength - 2) 285 System.arraycopy(oldList, i + 2, newList, i, 286 oldLength - 2 - i); 287 } 288 listenerList = newList; 289 return; 290 } 291 } 292 293 294 /** 295 * Returns a string representation of this object that may be useful 296 * for debugging purposes. 297 */ 298 public String toString() 299 { 300 CPStringBuilder buf = new CPStringBuilder("EventListenerList: "); 301 buf.append(listenerList.length / 2); 302 buf.append(" listeners: "); 303 for (int i = 0; i < listenerList.length; i += 2) 304 { 305 buf.append(" type "); 306 buf.append(((Class) listenerList[i]).getName()); 307 buf.append(" listener "); 308 buf.append(listenerList[i + 1]); 309 } 310 return buf.toString(); 311 } 312 313 /** 314 * Serializes an instance to an ObjectOutputStream. 315 * 316 * @param out the stream to serialize to 317 * 318 * @throws IOException if something goes wrong 319 */ 320 private void writeObject(ObjectOutputStream out) 321 throws IOException 322 { 323 out.defaultWriteObject(); 324 for (int i = 0; i < listenerList.length; i += 2) 325 { 326 Class cl = (Class) listenerList[i]; 327 EventListener l = (EventListener) listenerList[i + 1]; 328 if (l != null && l instanceof Serializable) 329 { 330 out.writeObject(cl.getName()); 331 out.writeObject(l); 332 } 333 } 334 // Write end marker. 335 out.writeObject(null); 336 } 337 338 /** 339 * Deserializes an instance from an ObjectInputStream. 340 * 341 * @param in the input stream 342 * 343 * @throws ClassNotFoundException if a serialized class can't be found 344 * @throws IOException if something goes wrong 345 */ 346 private <T extends EventListener> void readObject(ObjectInputStream in) 347 throws ClassNotFoundException, IOException 348 { 349 listenerList = NO_LISTENERS; 350 in.defaultReadObject(); 351 Object type; 352 ClassLoader cl = Thread.currentThread().getContextClassLoader(); 353 while ((type = in.readObject()) != null) 354 { 355 EventListener l = (EventListener) in.readObject(); 356 add(((Class<T>) Class.forName((String) type, true, cl)), (T) l); 357 } 358 } 359}