ItemEvent


1   /*
2    * @(#)ItemEvent.java   1.28 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 java.awt.event;
9   
10  import java.awt.Component  ;
11  import java.awt.AWTEvent  ;
12  import java.awt.Event  ;
13  import java.awt.ItemSelectable  ;
14  
15  /**
16   * A semantic event which indicates that an item was selected or deselected.
17   * This high-level event is generated by an ItemSelectable object (such as a 
18   * List) when an item is selected or deselected by the user.
19   * The event is passed to every <code>ItemListener</code> object which
20   * registered to receive such events using the component's
21   * <code>addItemListener</code> method. 
22   * <P>
23   * The object that implements the <code>ItemListener</code> interface gets
24   * this <code>ItemEvent</code> when the event occurs. The listener is
25   * spared the details of processing individual mouse movements and mouse
26   * clicks, and can instead process a "meaningful" (semantic) event like
27   * "item selected" or "item deselected". 
28   *
29   * @version 1.28 12/19/03
30   * @author Carl Quinn
31   *
32   * @see java.awt.ItemSelectable
33   * @see ItemListener
34   * @see <a HREF="http://java.sun.com/docs/books/tutorial/post1.0/ui/itemlistener.html">Tutorial: Writing an Item Listener</a>
35   * @see <a HREF="http://www.awl.com/cp/javaseries/jcl1_2.html">Reference: The Java Class Libraries (update file)</a>
36   *
37   * @since 1.1
38   */
39  public class ItemEvent extends AWTEvent   {
40  
41      /**
42       * The first number in the range of ids used for item events.
43       */
44      public static final int ITEM_FIRST      = 701;
45  
46      /**
47       * The last number in the range of ids used for item events.
48       */
49      public static final int ITEM_LAST       = 701;
50  
51      /** 
52       * This event id indicates that an item's state changed.
53       */
54      public static final int ITEM_STATE_CHANGED  = ITEM_FIRST; //Event.LIST_SELECT 
55  
56      /**
57       * This state-change value indicates that an item was selected.
58       */
59      public static final int SELECTED = 1;
60  
61      /** 
62       * This state-change-value indicates that a selected item was deselected.
63       */
64      public static final int DESELECTED  = 2;
65  
66      /**
67       * The item whose selection state has changed.
68       *
69       * @serial
70       * @see #getItem()
71       */
72      Object   item;
73  
74      /**
75       * <code>stateChange</code> indicates whether the <code>item</code>
76       * was selected or deselected.
77       *
78       * @serial
79       * @see #getStateChange()
80       */
81      int stateChange;
82  
83      /*
84       * JDK 1.1 serialVersionUID 
85       */
86      private static final long serialVersionUID = -608708132447206933L;
87  
88      /**
89       * Constructs an <code>ItemEvent</code> object.
90       * <p>Note that passing in an invalid <code>id</code> results in
91       * unspecified behavior. This method throws an
92       * <code>IllegalArgumentException</code> if <code>source</code>
93       * is <code>null</code>.
94       *
95       * @param source the <code>ItemSelectable</code> object
96       *               that originated the event
97       * @param id     an integer that identifies the event type
98       * @param item   an object -- the item affected by the event
99       * @param stateChange 
100      *               an integer that indicates whether the item was
101      *               selected or deselected
102      * @throws IllegalArgumentException if <code>source</code> is null
103      */
104     public ItemEvent(ItemSelectable   source, int id, Object   item, int stateChange) {
105         super(source, id);
106     this.item = item;
107         this.stateChange = stateChange;
108     }
109 
110     /**
111      * Returns the originator of the event.
112      *
113      * @return the ItemSelectable object that originated the event.
114      */
115     public ItemSelectable   getItemSelectable() {
116         return (ItemSelectable  )source;
117     }
118 
119    /**
120     * Returns the item affected by the event.
121     *
122     * @return the item (object) that was affected by the event
123     */
124     public Object   getItem() {
125         return item;
126     }
127 
128    /**
129     * Returns the type of state change (selected or deselected).
130     *
131     * @return an integer that indicates whether the item was selected
132     *         or deselected
133     *
134     * @see #SELECTED
135     * @see #DESELECTED
136     */
137     public int getStateChange() {
138         return stateChange;
139     }
140 
141     /**
142      * Returns a parameter string identifying this item event.
143      * This method is useful for event-logging and for debugging.
144      *
145      * @return a string identifying the event and its attributes
146      */
147     public String   paramString() {
148         String   typeStr;
149         switch(id) {
150           case ITEM_STATE_CHANGED:
151               typeStr = "ITEM_STATE_CHANGED";
152               break;
153           default:
154               typeStr = "unknown type";
155         }
156 
157         String   stateStr;
158         switch(stateChange) {
159           case SELECTED:
160               stateStr = "SELECTED";
161               break;
162           case DESELECTED:
163               stateStr = "DESELECTED";
164               break;
165           default:
166               stateStr = "unknown type";
167         }
168         return typeStr + ",item="+item + ",stateChange="+stateStr;
169     }
170 
171 }
172
A to Z: JavaDoc & Examples Daily Java News & Articles Open Source Projects Open Source Codes Free Computer Books Remove Frame
Popular Tags