svn-gvsig-desktop / branches / v2_0_0_prep / libraries / libTools / src / org / gvsig / tools / observer / impl / BaseWeakReferencingObservable.java @ 27337
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1 | 23170 | jmvivo | /* gvSIG. Geographic Information System of the Valencian Government
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2 | *
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3 | * Copyright (C) 2007-2008 Infrastructures and Transports Department
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4 | * of the Valencian Government (CIT)
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5 | *
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6 | * This program is free software; you can redistribute it and/or
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7 | * modify it under the terms of the GNU General Public License
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8 | * as published by the Free Software Foundation; either version 2
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9 | * of the License, or (at your option) any later version.
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10 | *
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11 | * This program is distributed in the hope that it will be useful,
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12 | * but WITHOUT ANY WARRANTY; without even the implied warranty of
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13 | * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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14 | * GNU General Public License for more details.
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15 | *
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16 | * You should have received a copy of the GNU General Public License
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17 | * along with this program; if not, write to the Free Software
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18 | * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston,
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19 | * MA 02110-1301, USA.
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20 | *
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21 | */
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22 | |||
23 | /*
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24 | * AUTHORS (In addition to CIT):
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25 | * 2008 IVER T.I. S.A. {{Task}}
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26 | */
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27 | 24178 | cordinyana | package org.gvsig.tools.observer.impl; |
28 | 23063 | jmvivo | |
29 | import java.lang.ref.Reference; |
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30 | import java.lang.ref.WeakReference; |
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31 | import java.util.ArrayList; |
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32 | import java.util.Iterator; |
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33 | 24178 | cordinyana | import java.util.List; |
34 | 23063 | jmvivo | |
35 | 24267 | jjdelcerro | import org.gvsig.tools.observer.ComplexWeakReferencingObservable; |
36 | 27337 | jmvivo | import org.gvsig.tools.observer.Observer; |
37 | 24267 | jjdelcerro | import org.gvsig.tools.observer.WeakReferencingObservable; |
38 | 23063 | jmvivo | |
39 | 24178 | cordinyana | /**
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40 | * Implementation for observers based on the use of Reference, instead of direct
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41 | * Observer references.
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42 | 27337 | jmvivo | *
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43 | 24178 | cordinyana | * This way an Observer may be Garbagge collected if its unique reference is the
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44 | * one registered into the Observable.
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45 | 27337 | jmvivo | *
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46 | 24178 | cordinyana | * @author <a href="mailto:josemanuel.vivo@iver.es">Jos? Manuel Viv?</a>
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47 | * @author <a href="mailto:cordin@disid.com">C?sar Ordi?ana</a>
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48 | */
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49 | 24267 | jjdelcerro | public class BaseWeakReferencingObservable implements ComplexWeakReferencingObservable { |
50 | 23063 | jmvivo | |
51 | 24178 | cordinyana | private boolean propageNotifications = true; |
52 | private boolean inComplex = false; |
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53 | private ComplexNotification complexNotification = null; |
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54 | 23063 | jmvivo | |
55 | 24178 | cordinyana | private boolean changed = false; |
56 | private List obs = new ArrayList(); |
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57 | 23063 | jmvivo | |
58 | /**
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59 | 24178 | cordinyana | * Adds an observer to the set of observers for this object, provided that
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60 | * it is not the same as some observer already in the set. The order in
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61 | * which notifications will be delivered to multiple observers is not
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62 | * specified. See the class comment.
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63 | 27337 | jmvivo | *
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64 | 24178 | cordinyana | * @param observer
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65 | * an observer to be added.
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66 | * @throws NullPointerException
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67 | * if the parameter o is null.
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68 | 23063 | jmvivo | */
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69 | 24178 | cordinyana | public void addObserver(Observer observer) { |
70 | addObserver(new WeakReference(observer)); |
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71 | 23063 | jmvivo | } |
72 | |||
73 | 24178 | cordinyana | public void addObserver(Reference ref) { |
74 | 23170 | jmvivo | if (ref == null || ref.get() == null) { |
75 | 24178 | cordinyana | throw new NullPointerException(); |
76 | } |
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77 | Observer observer = (Observer) ref.get(); |
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78 | synchronized (obs) {
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79 | if (!contains(observer)) {
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80 | obs.add(ref); |
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81 | } |
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82 | } |
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83 | 23063 | jmvivo | } |
84 | |||
85 | 24267 | jjdelcerro | public void addObservers(BaseWeakReferencingObservable observable) { |
86 | 24178 | cordinyana | observable.clearDeadReferences(); |
87 | Iterator iter = observable.obs.iterator();
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88 | while (iter.hasNext()) {
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89 | addObserver((Reference) iter.next());
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90 | } |
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91 | 23063 | jmvivo | |
92 | } |
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93 | |||
94 | /**
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95 | 24178 | cordinyana | * Deletes an observer from the set of observers of this object. Passing
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96 | * <CODE>null</CODE> to this method will have no effect.
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97 | 27337 | jmvivo | *
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98 | 24178 | cordinyana | * @param observer
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99 | * the observer to be deleted.
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100 | 23063 | jmvivo | */
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101 | 24178 | cordinyana | public void deleteObserver(Observer observer) { |
102 | deleteObserverReferenced(observer); |
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103 | 23063 | jmvivo | } |
104 | |||
105 | 24178 | cordinyana | public void deleteObserver(Reference ref) { |
106 | synchronized (obs) {
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107 | obs.remove(ref); |
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108 | 23063 | jmvivo | } |
109 | 24178 | cordinyana | deleteObserverReferenced((Observer) ref.get());
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110 | 23063 | jmvivo | } |
111 | |||
112 | /**
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113 | 24178 | cordinyana | * If this object has changed, as indicated by the <code>hasChanged</code>
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114 | * method, then notify all of its observers and then call the
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115 | * <code>clearChanged</code> method to indicate that this object has no
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116 | * longer changed.
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117 | 23063 | jmvivo | * <p>
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118 | * Each observer has its <code>update</code> method called with two
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119 | 24178 | cordinyana | * arguments: this observable object and <code>null</code>. In other words,
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120 | * this method is equivalent to: <blockquote><tt>
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121 | * notifyObservers(null)</tt>
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122 | * </blockquote>
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123 | 27337 | jmvivo | *
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124 | 24178 | cordinyana | * @see java.util.Observable#clearChanged()
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125 | * @see java.util.Observable#hasChanged()
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126 | * @see java.util.Observer#update(java.util.Observable, java.lang.Object)
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127 | 23063 | jmvivo | */
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128 | public void notifyObservers() { |
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129 | 24178 | cordinyana | notifyObservers(null);
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130 | 23063 | jmvivo | } |
131 | |||
132 | /**
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133 | 24178 | cordinyana | * If this object has changed, as indicated by the <code>hasChanged</code>
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134 | * method, then notify all of its observers and then call the
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135 | * <code>clearChanged</code> method to indicate that this object has no
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136 | * longer changed.
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137 | 23063 | jmvivo | * <p>
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138 | * Each observer has its <code>update</code> method called with two
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139 | * arguments: this observable object and the <code>arg</code> argument.
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140 | 27337 | jmvivo | *
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141 | 24178 | cordinyana | * @param arg
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142 | * any object.
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143 | * @see java.util.Observable#clearChanged()
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144 | * @see java.util.Observable#hasChanged()
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145 | * @see java.util.Observer#update(java.util.Observable, java.lang.Object)
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146 | 23063 | jmvivo | */
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147 | 24178 | cordinyana | public void notifyObservers(Object arg) { |
148 | if (!inComplex()) {
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149 | setChanged(); |
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150 | notify(this, arg);
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151 | } else {
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152 | complexNotification.addNotification(arg); |
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153 | } |
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154 | 23063 | jmvivo | |
155 | } |
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156 | |||
157 | /**
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158 | * Clears the observer list so that this object no longer has any observers.
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159 | */
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160 | 24178 | cordinyana | public void deleteObservers() { |
161 | synchronized (obs) {
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162 | obs.clear(); |
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163 | } |
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164 | 23063 | jmvivo | } |
165 | |||
166 | /**
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167 | 24178 | cordinyana | * Returns the number of observers of this object.
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168 | 27337 | jmvivo | *
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169 | 24178 | cordinyana | * @return the number of observers of this object.
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170 | 23063 | jmvivo | */
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171 | 24178 | cordinyana | public int countObservers() { |
172 | clearDeadReferences(); |
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173 | synchronized (obs) {
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174 | return obs.size();
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175 | } |
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176 | 23063 | jmvivo | } |
177 | |||
178 | 24178 | cordinyana | public void enableNotifications() { |
179 | clearDeadReferences(); |
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180 | propageNotifications = true;
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181 | 23063 | jmvivo | } |
182 | |||
183 | 24178 | cordinyana | public void disableNotifications() { |
184 | propageNotifications = false;
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185 | 23063 | jmvivo | } |
186 | |||
187 | 24178 | cordinyana | public boolean isEnabledNotifications() { |
188 | return propageNotifications;
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189 | 23063 | jmvivo | } |
190 | |||
191 | 24178 | cordinyana | public boolean inComplex() { |
192 | return inComplex;
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193 | } |
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194 | 23063 | jmvivo | |
195 | 24178 | cordinyana | public void beginComplexNotification() { |
196 | clearDeadReferences(); |
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197 | clearChanged(); |
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198 | inComplex = true;
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199 | complexNotification = new ComplexNotification();
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200 | complexNotification.clear(); |
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201 | } |
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202 | 23063 | jmvivo | |
203 | 24178 | cordinyana | public void endComplexNotification() { |
204 | inComplex = false;
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205 | 23063 | jmvivo | |
206 | 27337 | jmvivo | |
207 | 24178 | cordinyana | Iterator iter = complexNotification.getIterator();
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208 | while (iter.hasNext()) {
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209 | 27337 | jmvivo | setChanged(); |
210 | 24178 | cordinyana | notify(this, iter.next());
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211 | } |
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212 | complexNotification = null;
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213 | } |
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214 | 23063 | jmvivo | |
215 | 24267 | jjdelcerro | protected void notify(WeakReferencingObservable observable, Object object) { |
216 | 24178 | cordinyana | if (!isEnabledNotifications()) {
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217 | return;
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218 | 23063 | jmvivo | } |
219 | |||
220 | 24178 | cordinyana | /*
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221 | * a temporary array buffer, used as a snapshot of the state of current
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222 | * Observers.
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223 | 23063 | jmvivo | */
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224 | Object[] arrLocal; |
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225 | |||
226 | 24178 | cordinyana | synchronized (obs) {
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227 | /*
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228 | * We don't want the Observer doing callbacks into arbitrary code
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229 | * while holding its own Monitor. The code where we extract each
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230 | * DefaultObservable from the Vector and store the state of the
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231 | * Observer needs synchronization, but notifying observers does not
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232 | * (should not). The worst result of any potential race-condition
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233 | * here is that: 1) a newly-added Observer will miss a notification
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234 | * in progress 2) a recently unregistered Observer will be wrongly
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235 | * notified when it doesn't care
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236 | */
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237 | if (!changed) {
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238 | return;
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239 | } |
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240 | 23063 | jmvivo | arrLocal = obs.toArray(); |
241 | clearChanged(); |
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242 | } |
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243 | |||
244 | 24178 | cordinyana | // Go through all the registered observers and call update on them.
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245 | // If any of the Reference is null, remove it from the list.
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246 | for (int i = arrLocal.length - 1; i >= 0; i--) { |
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247 | Observer observer = (Observer) ((Reference) arrLocal[i]).get(); |
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248 | if (observer == null) { |
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249 | obs.remove(arrLocal[i]); |
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250 | } else {
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251 | observer.update(observable, object); |
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252 | } |
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253 | 23063 | jmvivo | } |
254 | 24178 | cordinyana | } |
255 | 23063 | jmvivo | |
256 | 24178 | cordinyana | /**
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257 | * Tests if this object has changed.
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258 | 27337 | jmvivo | *
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259 | 24178 | cordinyana | * @return <code>true</code> if and only if the <code>setChanged</code>
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260 | * method has been called more recently than the
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261 | * <code>clearChanged</code> method on this object;
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262 | * <code>false</code> otherwise.
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263 | * @see java.util.Observable#clearChanged()
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264 | * @see java.util.Observable#setChanged()
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265 | */
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266 | protected boolean hasChanged() { |
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267 | return changed;
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268 | } |
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269 | |||
270 | /**
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271 | * Marks this <tt>DefaultObservable</tt> object as having been changed; the
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272 | * <tt>hasChanged</tt> method will now return <tt>true</tt>.
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273 | */
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274 | protected void setChanged() { |
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275 | changed = true;
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276 | } |
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277 | |||
278 | /**
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279 | * Indicates that this object has no longer changed, or that it has already
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280 | * notified all of its observers of its most recent change, so that the
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281 | * <tt>hasChanged</tt> method will now return <tt>false</tt>. This method is
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282 | * called automatically by the <code>notifyObservers</code> methods.
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283 | 27337 | jmvivo | *
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284 | 24178 | cordinyana | * @see java.util.Observable#notifyObservers()
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285 | * @see java.util.Observable#notifyObservers(java.lang.Object)
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286 | */
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287 | protected void clearChanged() { |
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288 | changed = false;
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289 | } |
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290 | |||
291 | private void clearDeadReferences() { |
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292 | synchronized (obs) {
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293 | Iterator iter = obs.iterator();
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294 | while (iter.hasNext()) {
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295 | Object obj = iter.next();
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296 | if (obj instanceof Reference && ((Reference) obj).get() == null) { |
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297 | iter.remove(); |
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298 | } |
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299 | } |
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300 | 23063 | jmvivo | } |
301 | 24178 | cordinyana | } |
302 | 23063 | jmvivo | |
303 | 24178 | cordinyana | private boolean contains(Observer observer) { |
304 | synchronized (obs) {
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305 | Iterator iter = obs.iterator();
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306 | while (iter.hasNext()) {
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307 | Object obj = iter.next();
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308 | if (obj instanceof Reference) { |
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309 | Object value = ((Reference) obj).get(); |
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310 | if (observer.equals(value)) {
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311 | return true; |
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312 | } |
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313 | } |
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314 | } |
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315 | } |
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316 | return false; |
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317 | } |
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318 | |||
319 | private void deleteObserverReferenced(Observer observer) { |
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320 | if (observer == null) { |
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321 | return;
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322 | } |
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323 | synchronized (obs) {
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324 | Iterator iter = obs.iterator();
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325 | while (iter.hasNext()) {
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326 | Object obj = iter.next();
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327 | if (obj instanceof Reference) { |
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328 | Object value = ((Reference) obj).get(); |
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329 | if (value == null || observer.equals(value)) { |
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330 | iter.remove(); |
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331 | } |
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332 | } |
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333 | } |
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334 | } |
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335 | } |
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336 | } |