Spec-Zone .ru
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001/* 002 * Copyright (c) 2010, 2013, Oracle and/or its affiliates. All rights reserved. 003 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. 004 * 005 * This code is free software; you can redistribute it and/or modify it 006 * under the terms of the GNU General Public License version 2 only, as 007 * published by the Free Software Foundation. Oracle designates this 008 * particular file as subject to the "Classpath" exception as provided 009 * by Oracle in the LICENSE file that accompanied this code. 010 * 011 * This code is distributed in the hope that it will be useful, but WITHOUT 012 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or 013 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License 014 * version 2 for more details (a copy is included in the LICENSE file that 015 * accompanied this code). 016 * 017 * You should have received a copy of the GNU General Public License version 018 * 2 along with this work; if not, write to the Free Software Foundation, 019 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. 020 * 021 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA 022 * or visit www.oracle.com if you need additional information or have any 023 * questions. 024 */ 025 026package javafx.collections; 027 028import java.util.Collections; 029import java.util.List; 030 031/** 032 * Interface that receives notifications of changes to an ObservableList. 033 * 034 * @param <E> the list element type 035 * @see Change 036 */ 037public interface ListChangeListener<E> { 038 039 /** 040 * Represents a report of a changes done to an Observablelist. 041 * The Change may consist of one or more actual changes and must be iterated by {@link #next()} method. 042 * 043 * Each change must be one of the following: 044 * <ul> 045 * <li><b>Permutation change</b> : {@link #wasPermutated()} returns true in this case. 046 * The permutation happened at range between {@link #getFrom() from}(inclusive) and {@link #getTo() to}(exclusive) and 047 * can be queried by calling {@link #getPermutation(int)} method. 048 * <li><b>Add or remove change</b> : In this case, at least one of the {@link #wasAdded()}, {@link #wasRemoved()} returns true. 049 * If both methods return true, {@link #wasReplaced()} will also return true. 050 * <p>The {@link #getRemoved()} method returns a list of elements that have been 051 * replaced or removed from the list. 052 * <p> The range between {@link #getFrom() from}(inclusive) and {@link #getTo() to}(exclusive) 053 * denotes the sublist of the list that contain new elements. Note that this is a half-open 054 * interval, so if no elements were added, {@code getFrom()} is equal to {@code getTo()}. 055 * <p>It is possible to get a list of added elements by calling getAddedSubList(). 056 * <p>Note that in order to maintain correct indexes of the separate add/remove changes, these changes 057 * <b>must</b> be sorted by their {@code from} index. 058 * <li><b>Update change</b> : {@link #wasUpdated()} return true on an update change. 059 * All elements between {@link #getFrom() from}(inclusive) and {@link #getTo() to}(exclusive) were updated. 060 * </ul> 061 * 062 *<p> 063 * Typical usage is to observe changes on an ObservableList in order 064 * to hook or unhook (or add or remove a listener) or in order to maintain 065 * some invariant on every element in that ObservableList. A common code 066 * pattern for doing this looks something like the following:<br> 067 * 068 * <blockquote><pre> 069 * ObservableList<Item> theList = ...; 070 * 071 * theList.addListener(new ListChangeListener<Item>() { 072 * public void onChanged(Change<tem> c) { 073 * while (c.next()) { 074 * if (c.wasPermutated()) { 075 * for (int i = c.getFrom(); i < c.getTo(); ++i) { 076 * //permutate 077 * } 078 * } else if (c.wasUpdated()) { 079 * //update item 080 * } else { 081 * for (Item remitem : c.getRemoved()) { 082 * remitem.remove(Outer.this); 083 * } 084 * for (Item additem : c.getAddedSubList()) { 085 * additem.add(Outer.this); 086 * } 087 * } 088 * } 089 * } 090 * }); 091 * 092 * }</pre></blockquote> 093 * <p> 094 * <b>Warning:</b> This class directly accesses the source list to acquire information about the changes. 095 * <br> This effectively makes the Change object invalid when another change occurs on the list. 096 * <br> For this reason it is <b>not</b> safe to use this class on a different thread. 097 * <p> 098 * Note: in case the change contains multiple changes of different type, these changes must be in the following order: 099 * <em> permutation change(s), add or remove changes, update changes </em> 100 * This is because permutation changes cannot go after add/remove changes as they would change the position of added elements. 101 * And on the other hand, update changes must go after add/remove changes because they refer with their indexes to the current 102 * state of the list, which means with all add/remove changes applied. 103 * @param <E> the list element type 104 */ 105 public abstract static class Change<E> { 106 private final ObservableList<E> list; 107 108 /** 109 * Go to the next change. 110 * The Change in the initial state is invalid a requires a call to next() before 111 * calling other methods. The first next() call will make this object 112 * represent the first change. 113 * @return true if switched to the next change, false if this is the last change. 114 */ 115 public abstract boolean next(); 116 117 /** 118 * Reset to the initial stage. After this call, the next() must be called 119 * before working with the first change. 120 */ 121 public abstract void reset(); 122 123 /** 124 * Constructs a new change done to a list. 125 * @param list that was changed 126 */ 127 public Change(ObservableList<E> list) { 128 this.list = list; 129 } 130 131 /** 132 * The source list of the change. 133 * @return a list that was changed 134 */ 135 public ObservableList<E> getList() { 136 return list; 137 } 138 139 /** 140 * If wasAdded is true, the interval contains all the values that were added. 141 * If wasPermutated is true, the interval marks the values that were permutated. 142 * If wasRemoved is true and wasAdded is false, getFrom() and getTo() should 143 * return the same number - the place where the removed elements were positioned in the list. 144 * @return a beginning (inclusive) of an interval related to the change 145 * @throws IllegalStateException if this Change is in initial state 146 */ 147 public abstract int getFrom(); 148 /** 149 * The end of the change interval. 150 * @return a end (exclusive) of an interval related to the change. 151 * @throws IllegalStateException if this Change is in initial state 152 * @see #getFrom() 153 */ 154 public abstract int getTo(); 155 /** 156 * An immutable list of removed/replaced elements. If no elements 157 * were removed from the list, an empty list is returned. 158 * @return a list with all the removed elements 159 * @throws IllegalStateException if this Change is in initial state 160 */ 161 public abstract List<E> getRemoved(); 162 /** 163 * Indicates if the change was only a permutation. 164 * @return true if the change was just a permutation. 165 * @throws IllegalStateException if this Change is in initial state 166 */ 167 public boolean wasPermutated() { 168 return getPermutation().length != 0; 169 } 170 171 /** 172 * Indicates if elements were added during this change 173 * @return true if something was added to the list 174 * @throws IllegalStateException if this Change is in initial state 175 */ 176 public boolean wasAdded() { 177 return !wasPermutated() && !wasUpdated() && getFrom() < getTo(); 178 } 179 180 /** 181 * Indicates if elements were removed during this change. 182 * Note that using set will also produce a change with wasRemoved() returning 183 * true. See {@link #wasReplaced()}. 184 * @return true if something was removed from the list 185 * @throws IllegalStateException if this Change is in initial state 186 */ 187 public boolean wasRemoved() { 188 return !getRemoved().isEmpty(); 189 } 190 191 /** 192 * Indicates if elements were replaced during this change. 193 * This is usually true when set is called on the list. 194 * Set operation will act like remove and add operation at the same time. 195 * <p> 196 * Usually, it's not necessary to use this method directly. 197 * Handling remove operation and then add operation, as in the example {@link ListChangeListener$Change above}, 198 * will effectively handle also set operation. 199 * 200 * @return same <code> as wasAdded() && wasRemoved() </code> 201 * @throws IllegalStateException if this Change is in initial state 202 */ 203 public boolean wasReplaced() { 204 return wasAdded() && wasRemoved(); 205 } 206 207 /** 208 * Indicates that the elements between getFrom() (inclusive) 209 * to getTo() exclusive has changed. 210 * This is the only optional event type and may not be 211 * fired by all ObservableLists. 212 * @return true if the current change is an update change. 213 * @since 2.1 214 */ 215 public boolean wasUpdated() { 216 return false; 217 } 218 219 /** 220 * To get a subList view of the list that contains only the elements 221 * added, use getAddedSubList() method. 222 * This is actually a shortcut to <code>c.getList().subList(c.getFrom(), c.getTo());</code><br> 223 * 224 * <pre><code> 225 * for (Node n : change.getAddedSubList()) { 226 * // do something 227 * } 228 * </code></pre> 229 * @return the newly created sublist view that contains all the added elements. 230 * @throws IllegalStateException if this Change is in initial state 231 */ 232 public List<E> getAddedSubList() { 233 return wasAdded()? getList().subList(getFrom(), getTo()) : Collections.<E>emptyList(); 234 } 235 236 /** 237 * Size of getRemoved() list. 238 * @return the number of removed items 239 * @throws IllegalStateException if this Change is in initial state 240 */ 241 public int getRemovedSize() { 242 return getRemoved().size(); 243 } 244 245 /** 246 * Size of the interval that was added. 247 * @return the number of added items 248 * @throws IllegalStateException if this Change is in initial state 249 */ 250 public int getAddedSize() { 251 return wasAdded() ? getTo() - getFrom() : 0; 252 } 253 254 /** 255 * If this change is an permutation, it returns an integer array 256 * that describes the permutation. 257 * This array maps directly from the previous indexes to the new ones. 258 * This method is not publicly accessible and therefore can return an array safely. 259 * The 0 index of the array corresponds to index {@link #getFrom()} of the list. The same applies 260 * for the last index and {@link #getTo()}. 261 * The method is used by {@link #wasPermutated() } and {@link #getPermutation(int)} methods. 262 * @return empty array if this is not permutation or an integer array containing the permutation 263 * @throws IllegalStateException if this Change is in initial state 264 */ 265 protected abstract int[] getPermutation(); 266 267 /** 268 * By calling these method, you can observe the permutation that happened. 269 * In order to get the new position of an element, you must call: 270 * <pre> 271 * change.getPermutation(oldIndex); 272 * </pre> 273 * 274 * Note: default implementation of this method takes the information 275 * from {@link #getPermutation()} method. You don't have to override this method. 276 * @param i the old index that contained the element prior to this change 277 * @throws IndexOutOfBoundsException if i is out of the bounds of the list 278 * @throws IllegalStateException if this is not a permutation change 279 * @return the new index of the same element 280 */ 281 public int getPermutation(int i) { 282 if (!wasPermutated()) { 283 throw new IllegalStateException("Not a permutation change"); 284 } 285 return getPermutation()[i - getFrom()]; 286 } 287 288 } 289 /** 290 * Called after a change has been made to an ObservableList. 291 * 292 * @param c an object representing the change that was done 293 * @see Change 294 */ 295 public void onChanged(Change<? extends E> c); 296}