TreeModelEvent


1   /*
2    * @(#)TreeModelEvent.java  1.33 03/12/19
3    *
4    * Copyright 2004 Sun Microsystems, Inc. All rights reserved.
5    * SUN PROPRIETARY/CONFIDENTIAL. Use is subject to license terms.
6    */
7   
8   package javax.swing.event;
9   
10  import java.util.EventObject  ;
11  import javax.swing.tree.TreePath  ;
12  
13  
14  /**
15   * Encapsulates information describing changes to a tree model, and
16   * used to notify tree model listeners of the change.
17   * For more information and examples see
18   * <a
19   href="http://java.sun.com/docs/books/tutorial/uiswing/events/treemodellistener.html">How to Write a Tree Model Listener</a>,
20   * a section in <em>The Java Tutorial.</em>
21   * <p>
22   * <strong>Warning:</strong>
23   * Serialized objects of this class will not be compatible with
24   * future Swing releases. The current serialization support is
25   * appropriate for short term storage or RMI between applications running
26   * the same version of Swing.  As of 1.4, support for long term storage
27   * of all JavaBeans<sup><font size="-2">TM</font></sup>
28   * has been added to the <code>java.beans</code> package.
29   * Please see {@link java.beans.XMLEncoder}.
30   *
31   * @version 1.33 12/19/03
32   * @author Rob Davis
33   * @author Ray Ryan
34   * @author Scott Violet
35   */
36  public class TreeModelEvent extends EventObject   {
37      /** Path to the parent of the nodes that have changed. */
38      protected TreePath    path;
39      /** Indices identifying the position of where the children were. */
40      protected int[] childIndices;
41      /** Children that have been removed. */
42      protected Object  []  children;
43  
44      /**
45       * Used to create an event when nodes have been changed, inserted, or
46       * removed, identifying the path to the parent of the modified items as
47       * an array of Objects. All of the modified objects are siblings which are
48       * direct descendents (not grandchildren) of the specified parent.
49       * The positions at which the inserts, deletes, or changes occurred are
50       * specified by an array of <code>int</code>. The indexes in that array
51       * must be in order, from lowest to highest.
52       * <p>
53       * For changes, the indexes in the model correspond exactly to the indexes
54       * of items currently displayed in the UI. As a result, it is not really
55       * critical if the indexes are not in their exact order. But after multiple
56       * inserts or deletes, the items currently in the UI no longer correspond
57       * to the items in the model. It is therefore critical to specify the
58       * indexes properly for inserts and deletes.
59       * <p>
60       * For inserts, the indexes represent the <i>final</i> state of the tree,
61       * after the inserts have occurred. Since the indexes must be specified in
62       * order, the most natural processing methodology is to do the inserts
63       * starting at the lowest index and working towards the highest. Accumulate
64       * a Vector of <code>Integer</code> objects that specify the
65       * insert-locations as you go, then convert the Vector to an
66       * array of <code>int</code> to create the event. When the postition-index
67       * equals zero, the node is inserted at the beginning of the list. When the
68       * position index equals the size of the list, the node is "inserted" at
69       * (appended to) the end of the list.
70       * <p>
71       * For deletes, the indexes represent the <i>initial</i> state of the tree,
72       * before the deletes have occurred. Since the indexes must be specified in
73       * order, the most natural processing methodology is to use a delete-counter.
74       * Start by initializing the counter to zero and start work through the
75       * list from lowest to higest. Every time you do a delete, add the current
76       * value of the delete-counter to the index-position where the delete occurred,
77       * and append the result to a Vector of delete-locations, using
78       * <code>addElement()</code>. Then increment the delete-counter. The index
79       * positions stored in the Vector therefore reflect the effects of all previous
80       * deletes, so they represent each object's position in the initial tree.
81       * (You could also start at the highest index and working back towards the
82       * lowest, accumulating a Vector of delete-locations as you go using the
83       * <code>insertElementAt(Integer, 0)</code>.) However you produce the Vector
84       * of initial-positions, you then need to convert the Vector of <code>Integer</code>
85       * objects to an array of <code>int</code> to create the event.
86       * <p>
87       * <b>Notes:</b><ul>
88       * <li>Like the <code>insertNodeInto</code> method in the
89       *    <code>DefaultTreeModel</code> class, <code>insertElementAt</code>
90       *    appends to the <code>Vector</code> when the index matches the size
91       *    of the vector. So you can use <code>insertElementAt(Integer, 0)</code>
92       *    even when the vector is empty.
93       * <ul>To create a node changed event for the root node, specify the parent
94       *     and the child indices as <code>null</code>.
95       * </ul>
96       *
97       * @param source the Object responsible for generating the event (typically
98       *               the creator of the event object passes <code>this</code>
99       *               for its value)
100      * @param path   an array of Object identifying the path to the
101      *               parent of the modified item(s), where the first element
102      *               of the array is the Object stored at the root node and
103      *               the last element is the Object stored at the parent node
104      * @param childIndices an array of <code>int</code> that specifies the
105      *               index values of the removed items. The indices must be
106      *               in sorted order, from lowest to highest
107      * @param children an array of Object containing the inserted, removed, or
108      *                 changed objects
109      * @see TreePath
110      */
111     public TreeModelEvent(Object   source, Object  [] path, int[] childIndices,
112               Object  [] children)
113     {
114     this(source, new TreePath  (path), childIndices, children);
115     }
116 
117     /**
118      * Used to create an event when nodes have been changed, inserted, or
119      * removed, identifying the path to the parent of the modified items as
120      * a TreePath object. For more information on how to specify the indexes
121      * and objects, see
122      * <code>TreeModelEvent(Object,Object[],int[],Object[])</code>.
123      *
124      * @param source the Object responsible for generating the event (typically
125      *               the creator of the event object passes <code>this</code>
126      *               for its value)
127      * @param path   a TreePath object that identifies the path to the
128      *               parent of the modified item(s)
129      * @param childIndices an array of <code>int</code> that specifies the
130      *               index values of the modified items
131      * @param children an array of Object containing the inserted, removed, or
132      *                 changed objects
133      *
134      * @see #TreeModelEvent(Object,Object[],int[],Object[])
135      */
136     public TreeModelEvent(Object   source, TreePath   path, int[] childIndices,
137               Object  [] children)
138     {
139     super(source);
140     this.path = path;
141     this.childIndices = childIndices;
142     this.children = children;
143     }
144 
145     /**
146      * Used to create an event when the node structure has changed in some way,
147      * identifying the path to the root of a modified subtree as an array of
148      * Objects. A structure change event might involve nodes swapping position,
149      * for example, or it might encapsulate multiple inserts and deletes in the
150      * subtree stemming from the node, where the changes may have taken place at
151      * different levels of the subtree.
152      * <blockquote>
153      *   <b>Note:</b><br>
154      *   JTree collapses all nodes under the specified node, so that only its
155      *   immediate children are visible.
156      * </blockquote>
157      *
158      * @param source the Object responsible for generating the event (typically
159      *               the creator of the event object passes <code>this</code>
160      *               for its value)
161      * @param path   an array of Object identifying the path to the root of the
162      *               modified subtree, where the first element of the array is
163      *               the object stored at the root node and the last element
164      *               is the object stored at the changed node
165      * @see TreePath
166      */
167     public TreeModelEvent(Object   source, Object  [] path)
168     {
169     this(source, new TreePath  (path));
170     }
171 
172     /**
173      * Used to create an event when the node structure has changed in some way,
174      * identifying the path to the root of the modified subtree as a TreePath
175      * object. For more information on this event specification, see
176      * <code>TreeModelEvent(Object,Object[])</code>.
177      *
178      * @param source the Object responsible for generating the event (typically
179      *               the creator of the event object passes <code>this</code>
180      *               for its value)
181      * @param path   a TreePath object that identifies the path to the
182      *               change. In the DefaultTreeModel,
183      *               this object contains an array of user-data objects,
184      *               but a subclass of TreePath could use some totally
185      *               different mechanism -- for example, a node ID number
186      *
187      * @see #TreeModelEvent(Object,Object[])
188      */
189     public TreeModelEvent(Object   source, TreePath   path)
190     {
191     super(source);
192     this.path = path;
193     this.childIndices = new int[0];
194     }
195 
196     /**
197      * For all events, except treeStructureChanged,
198      * returns the parent of the changed nodes.
199      * For treeStructureChanged events, returns the ancestor of the
200      * structure that has changed. This and
201      * <code>getChildIndices</code> are used to get a list of the effected
202      * nodes.
203      * <p>
204      * The one exception to this is a treeNodesChanged event that is to
205      * identify the root, in which case this will return the root
206      * and <code>getChildIndices</code> will return null.
207      *
208      * @return the TreePath used in identifying the changed nodes.
209      * @see TreePath#getLastPathComponent
210      */
211     public TreePath   getTreePath() { return path; }
212 
213     /**
214      * Convenience method to get the array of objects from the TreePath
215      * instance that this event wraps.
216      *
217      * @return an array of Objects, where the first Object is the one
218      *         stored at the root and the last object is the one
219      *         stored at the node identified by the path
220      */
221     public Object  [] getPath() {
222     if(path != null)
223         return path.getPath();
224     return null;
225     }
226 
227     /**
228      * Returns the objects that are children of the node identified by
229      * <code>getPath</code> at the locations specified by
230      * <code>getChildIndices</code>. If this is a removal event the
231      * returned objects are no longer children of the parent node.
232      *
233      * @return an array of Object containing the children specified by
234      *         the event
235      * @see #getPath
236      * @see #getChildIndices
237      */
238     public Object  [] getChildren() {
239     if(children != null) {
240         int            cCount = children.length;
241         Object  []       retChildren = new Object  [cCount];
242 
243         System.arraycopy(children, 0, retChildren, 0, cCount);
244         return retChildren;
245     }
246     return null;
247     }
248 
249     /**
250      * Returns the values of the child indexes. If this is a removal event
251      * the indexes point to locations in the initial list where items
252      * were removed. If it is an insert, the indices point to locations
253      * in the final list where the items were added. For node changes,
254      * the indices point to the locations of the modified nodes.
255      *
256      * @return an array of <code>int</code> containing index locations for
257      *         the children specified by the event
258      */
259     public int[] getChildIndices() {
260     if(childIndices != null) {
261         int            cCount = childIndices.length;
262         int[]          retArray = new int[cCount];
263 
264         System.arraycopy(childIndices, 0, retArray, 0, cCount);
265         return retArray;
266     }
267     return null;
268     }
269 
270     /**
271      * Returns a string that displays and identifies this object's
272      * properties.
273      *
274      * @return a String representation of this object
275      */
276     public String   toString() {
277     StringBuffer     retBuffer = new StringBuffer  ();
278 
279     retBuffer.append(getClass().getName() + " " +
280              Integer.toString(hashCode()));
281     if(path != null)
282         retBuffer.append(" path " + path);
283     if(childIndices != null) {
284         retBuffer.append(" indices [ ");
285         for(int counter = 0; counter < childIndices.length; counter++)
286         retBuffer.append(Integer.toString(childIndices[counter])+ " ");
287         retBuffer.append("]");
288     }
289     if(children != null) {
290         retBuffer.append(" children [ ");
291         for(int counter = 0; counter < children.length; counter++)
292         retBuffer.append(children[counter] + " ");
293         retBuffer.append("]");
294     }
295     return retBuffer.toString();
296     }
297 }
298
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