HandlerEvent


1   /*******************************************************************************
2    * Copyright (c) 2003, 2006 IBM Corporation and others.
3    * All rights reserved. This program and the accompanying materials
4    * are made available under the terms of the Eclipse Public License v1.0
5    * which accompanies this distribution, and is available at
6    * http://www.eclipse.org/legal/epl-v10.html
7    *
8    * Contributors:
9    *     IBM Corporation - initial API and implementation
10   *******************************************************************************/
11  package org.eclipse.ui.commands;
12  
13  import java.util.Map  ;
14  
15  import org.eclipse.ui.internal.util.Util;
16  
17  /**
18   * An instance of this class describes changes to an instance of
19   * <code>IHandler</code>.
20   * <p>
21   * This class is not intended to be extended by clients.
22   * </p>
23   * 
24   * @since 3.0
25   * @see IHandlerListener#handlerChanged(HandlerEvent)
26   * @deprecated Please use the "org.eclipse.core.commands" plug-in instead.
27   */
28  public final class HandlerEvent {
29  
30      /**
31       * Whether the attributes of the handler changed.
32       */
33      private final boolean attributeValuesByNameChanged;
34  
35      /**
36       * The handler that changed; this value is never <code>null</code>.
37       */
38      private final IHandler handler;
39  
40      /**
41       * This is the cached result of getPreviousAttributeValuesByName. It is
42       * computed the first time getPreviousAttributeValuesByName is called.
43       */
44      private Map   previousAttributeValuesByName;
45  
46      /**
47       * The map of previous attributes, if they changed.  If they did not change,
48       * then this value is <code>null</code>.  The map's keys are the attribute
49       * names (strings), and its value are any object.
50       * 
51       * This is the original map passed into the constructor. This object always
52       * returns a copy of this map, not the original. However the constructor of
53       * this object is called very frequently and the map is rarely requested,
54       * so we only copy the map the first time it is requested. 
55       * 
56       * @since 3.1
57       */
58      private final Map   originalPreviousAttributeValuesByName;
59      
60      /**
61       * Creates a new instance of this class.
62       * 
63       * @param handler
64       *            the instance of the interface that changed.
65       * @param attributeValuesByNameChanged
66       *            true, iff the attributeValuesByName property changed.
67       * @param previousAttributeValuesByName
68       *            the map of previous attribute values by name. This map may be
69       *            empty. If this map is not empty, it's collection of keys must
70       *            only contain instances of <code>String</code>. This map
71       *            must be <code>null</code> if attributeValuesByNameChanged is
72       *            <code>false</code> and must not be null if
73       *            attributeValuesByNameChanged is <code>true</code>.
74       */
75      public HandlerEvent(IHandler handler, boolean attributeValuesByNameChanged,
76              Map   previousAttributeValuesByName) {
77          if (handler == null) {
78              throw new NullPointerException  ();
79          }
80  
81          if (!attributeValuesByNameChanged
82                  && previousAttributeValuesByName != null) {
83              throw new IllegalArgumentException  ();
84          }
85  
86          if (attributeValuesByNameChanged) {
87              this.originalPreviousAttributeValuesByName = previousAttributeValuesByName;
88          } else {
89              this.originalPreviousAttributeValuesByName = null;
90          }
91  
92          this.handler = handler;
93          this.attributeValuesByNameChanged = attributeValuesByNameChanged;
94      }
95  
96      /**
97       * Returns the instance of the interface that changed.
98       * 
99       * @return the instance of the interface that changed. Guaranteed not to be
100      *         <code>null</code>.
101      */
102     public IHandler getHandler() {
103         return handler;
104     }
105 
106     /**
107      * Returns the map of previous attribute values by name.
108      * 
109      * @return the map of previous attribute values by name. This map may be
110      *         empty. If this map is not empty, it's collection of keys is
111      *         guaranteed to only contain instances of <code>String</code>.
112      *         This map is guaranteed to be <code>null</code> if
113      *         haveAttributeValuesByNameChanged() is <code>false</code> and is
114      *         guaranteed to not be null if haveAttributeValuesByNameChanged()
115      *         is <code>true</code>.
116      */
117     public Map   getPreviousAttributeValuesByName() {
118         if (originalPreviousAttributeValuesByName == null) {
119             return null;
120         }
121         
122         if (previousAttributeValuesByName == null) {
123             previousAttributeValuesByName = Util.safeCopy(
124                     originalPreviousAttributeValuesByName, String  .class, Object  .class,
125                     false, true);
126         }
127         
128         return previousAttributeValuesByName;
129     }
130 
131     /**
132      * Returns whether or not the attributeValuesByName property changed.
133      * 
134      * @return true, iff the attributeValuesByName property changed.
135      */
136     public boolean haveAttributeValuesByNameChanged() {
137         return attributeValuesByNameChanged;
138     }
139 }
140
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