001 /* EventListenerList.java -- 002 Copyright (C) 2002, 2004, 2005, 2006, Free Software Foundation, Inc. 003 004 This file is part of GNU Classpath. 005 006 GNU Classpath is free software; you can redistribute it and/or modify 007 it under the terms of the GNU General Public License as published by 008 the Free Software Foundation; either version 2, or (at your option) 009 any later version. 010 011 GNU Classpath is distributed in the hope that it will be useful, but 012 WITHOUT ANY WARRANTY; without even the implied warranty of 013 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU 014 General Public License for more details. 015 016 You should have received a copy of the GNU General Public License 017 along with GNU Classpath; see the file COPYING. If not, write to the 018 Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 019 02110-1301 USA. 020 021 Linking this library statically or dynamically with other modules is 022 making a combined work based on this library. Thus, the terms and 023 conditions of the GNU General Public License cover the whole 024 combination. 025 026 As a special exception, the copyright holders of this library give you 027 permission to link this library with independent modules to produce an 028 executable, regardless of the license terms of these independent 029 modules, and to copy and distribute the resulting executable under 030 terms of your choice, provided that you also meet, for each linked 031 independent module, the terms and conditions of the license of that 032 module. An independent module is a module which is not derived from 033 or based on this library. If you modify this library, you may extend 034 this exception to your version of the library, but you are not 035 obligated to do so. If you do not wish to do so, delete this 036 exception statement from your version. */ 037 038 package javax.swing.event; 039 040 import java.io.IOException; 041 import java.io.ObjectInputStream; 042 import java.io.ObjectOutputStream; 043 import java.io.Serializable; 044 import java.lang.reflect.Array; 045 import java.util.EventListener; 046 047 048 /** 049 * A utility class for keeping track of {@link EventListener}s. 050 * 051 * <p><b>Example for using this class:</b> 052 * 053 * <blockquote><pre> import java.util.EventListener; 054 * import javax.swing.event.EventListenerList; 055 * 056 * class Foo 057 * { 058 * protected final EventListenerList listeners = new EventListenerList(); 059 * protected BarClosedEvent barClosedEvent = null; 060 * 061 * public void addBarListener(BarListener l) 062 * { 063 * listeners.<a href="#add(java.lang.Class, java.util.EventListener)" 064 * >add</a>(BarListener.class, l); 065 * } 066 * 067 * public void removeBarListener(BarListener l) 068 * { 069 * listeners.<a href="#remove(java.lang.Class, java.util.EventListener)" 070 * >remove</a>(BarListener.class, l); 071 * } 072 * 073 * protected void fireBarClosedEvent() 074 * { 075 * Object[] l = listeners.<a href="#getListenerList()" 076 * >getListenerList()</a>; 077 * 078 * for (int i = l.length - 2; i >= 0; i -= 2) 079 * if (l[i] == BarListener.class) 080 * { 081 * // Create the event on demand, when it is needed the first time. 082 * if (barClosedEvent == null) 083 * barClosedEvent = new BarClosedEvent(this); 084 * 085 * ((BarClosedListener) l[i + 1]).barClosed(barClosedEvent); 086 * } 087 * } 088 * }</pre></blockquote> 089 * 090 * @author Andrew Selkirk (aselkirk@sympatico.ca) 091 * @author Sascha Brawer (brawer@dandelis.ch) 092 */ 093 public class EventListenerList 094 implements Serializable 095 { 096 /** 097 * An ID for serializing instances of this class; verified with the 098 * serialver tool of Sun J2SE 1.4.1_01. 099 */ 100 static final long serialVersionUID = -5677132037850737084L; 101 102 103 /** 104 * An empty array that is shared by all instances of this class that 105 * have no listeners. 106 */ 107 private static final Object[] NO_LISTENERS = new Object[0]; 108 109 110 /** 111 * An array with all currently registered listeners. The array has 112 * twice as many elements as there are listeners. For an even 113 * integer <code>i</code>, <code>listenerList[i]</code> indicates 114 * the registered class, and <code>listenerList[i + 1]</code> is the 115 * listener. 116 */ 117 protected transient Object[] listenerList = NO_LISTENERS; 118 119 120 /** 121 * EventListenerList constructor 122 */ 123 public EventListenerList() 124 { 125 // Nothing to do here. 126 } 127 128 129 /** 130 * Registers a listener of a specific type. 131 * 132 * @param t the type of the listener. 133 * 134 * @param listener the listener to add, which must be an instance of 135 * <code>t</code>, or of a subclass of <code>t</code>. 136 * 137 * @throws IllegalArgumentException if <code>listener</code> is not 138 * an instance of <code>t</code> (or a subclass thereof). 139 * 140 * @throws NullPointerException if <code>t</code> is <code>null</code>. 141 */ 142 public <T extends EventListener> void add(Class<T> t, T listener) 143 { 144 int oldLength; 145 Object[] newList; 146 147 if (listener == null) 148 return; 149 150 if (!t.isInstance(listener)) 151 throw new IllegalArgumentException(); 152 153 oldLength = listenerList.length; 154 newList = new Object[oldLength + 2]; 155 if (oldLength > 0) 156 System.arraycopy(listenerList, 0, newList, 0, oldLength); 157 158 newList[oldLength] = t; 159 newList[oldLength + 1] = listener; 160 listenerList = newList; 161 } 162 163 164 /** 165 * Determines the number of listeners. 166 */ 167 public int getListenerCount() 168 { 169 return listenerList.length / 2; 170 } 171 172 173 /** 174 * Determines the number of listeners of a particular class. 175 * 176 * @param t the type of listeners to be counted. In order to get 177 * counted, a subscribed listener must be exactly of class 178 * <code>t</code>. Thus, subclasses of <code>t</code> will not be 179 * counted. 180 */ 181 public int getListenerCount(Class<?> t) 182 { 183 int result = 0; 184 for (int i = 0; i < listenerList.length; i += 2) 185 if (t == listenerList[i]) 186 ++result; 187 188 return result; 189 } 190 191 192 /** 193 * Returns an array containing a sequence of listenerType/listener pairs, one 194 * for each listener. 195 * 196 * @return An array containing the listener types and references. 197 */ 198 public Object[] getListenerList() 199 { 200 // returning the internal storage is a bad idea, but tests show that the 201 // reference implementation does this... 202 return listenerList; 203 } 204 205 206 /** 207 * Retrieves the currently subscribed listeners of a particular 208 * type. For a listener to be returned, it must have been 209 * registered with exactly the type <code>c</code>; subclasses are 210 * not considered equal. 211 * 212 * <p>The returned array can always be cast to <code>c[]</code>. 213 * Since it is a newly allocated copy, the caller may arbitrarily 214 * modify the array. 215 * 216 * @param c the class which was passed to {@link #add}. 217 * 218 * @throws ClassCastException if <code>c</code> does not implement 219 * the {@link EventListener} interface. 220 * 221 * @throws NullPointerException if <code>c</code> is 222 * <code>null</code>. 223 * 224 * @return an array of <code>c</code> whose elements are the 225 * currently subscribed listeners of the specified type. If there 226 * are no such listeners, an empty array is returned. 227 * 228 * @since 1.3 229 */ 230 public <T extends EventListener> T[] getListeners(Class<T> c) 231 { 232 int count, f; 233 EventListener[] result; 234 235 count = getListenerCount(c); 236 result = (EventListener[]) Array.newInstance(c, count); 237 f = 0; 238 for (int i = listenerList.length - 2; i >= 0; i -= 2) 239 if (listenerList[i] == c) 240 result[f++] = (EventListener) listenerList[i + 1]; 241 242 return (T[]) result; 243 } 244 245 246 /** 247 * Removes a listener of a specific type. 248 * 249 * @param t the type of the listener. 250 * 251 * @param listener the listener to remove, which must be an instance 252 * of <code>t</code>, or of a subclass of <code>t</code>. 253 * 254 * @throws IllegalArgumentException if <code>listener</code> is not 255 * an instance of <code>t</code> (or a subclass thereof). 256 * 257 * @throws NullPointerException if <code>t</code> is <code>null</code>. 258 */ 259 public <T extends EventListener> void remove(Class<T> t, T listener) 260 { 261 Object[] oldList, newList; 262 int oldLength; 263 264 if (listener == null) 265 return; 266 267 if (!t.isInstance(listener)) 268 throw new IllegalArgumentException(); 269 270 oldList = listenerList; 271 oldLength = oldList.length; 272 for (int i = 0; i < oldLength; i += 2) 273 if (oldList[i] == t && oldList[i + 1] == listener) 274 { 275 if (oldLength == 2) 276 newList = NO_LISTENERS; 277 else 278 { 279 newList = new Object[oldLength - 2]; 280 if (i > 0) 281 System.arraycopy(oldList, 0, newList, 0, i); 282 if (i < oldLength - 2) 283 System.arraycopy(oldList, i + 2, newList, i, 284 oldLength - 2 - i); 285 } 286 listenerList = newList; 287 return; 288 } 289 } 290 291 292 /** 293 * Returns a string representation of this object that may be useful 294 * for debugging purposes. 295 */ 296 public String toString() 297 { 298 StringBuffer buf = new StringBuffer("EventListenerList: "); 299 buf.append(listenerList.length / 2); 300 buf.append(" listeners: "); 301 for (int i = 0; i < listenerList.length; i += 2) 302 { 303 buf.append(" type "); 304 buf.append(((Class) listenerList[i]).getName()); 305 buf.append(" listener "); 306 buf.append(listenerList[i + 1]); 307 } 308 return buf.toString(); 309 } 310 311 /** 312 * Serializes an instance to an ObjectOutputStream. 313 * 314 * @param out the stream to serialize to 315 * 316 * @throws IOException if something goes wrong 317 */ 318 private void writeObject(ObjectOutputStream out) 319 throws IOException 320 { 321 out.defaultWriteObject(); 322 for (int i = 0; i < listenerList.length; i += 2) 323 { 324 Class cl = (Class) listenerList[i]; 325 EventListener l = (EventListener) listenerList[i + 1]; 326 if (l != null && l instanceof Serializable) 327 { 328 out.writeObject(cl.getName()); 329 out.writeObject(l); 330 } 331 } 332 // Write end marker. 333 out.writeObject(null); 334 } 335 336 /** 337 * Deserializes an instance from an ObjectInputStream. 338 * 339 * @param in the input stream 340 * 341 * @throws ClassNotFoundException if a serialized class can't be found 342 * @throws IOException if something goes wrong 343 */ 344 private <T extends EventListener> void readObject(ObjectInputStream in) 345 throws ClassNotFoundException, IOException 346 { 347 listenerList = NO_LISTENERS; 348 in.defaultReadObject(); 349 Object type; 350 ClassLoader cl = Thread.currentThread().getContextClassLoader(); 351 while ((type = in.readObject()) != null) 352 { 353 EventListener l = (EventListener) in.readObject(); 354 add(((Class<T>) Class.forName((String) type, true, cl)), (T) l); 355 } 356 } 357 }