CBJComboBox


1   package com.ca.commons.cbutil;
2   
3   import javax.swing.*;
4   import java.util.Vector  ;
5   
6   
7   /**
8    * A JComboBox that sets the KeySelectionManager in the constructors.
9    *
10   * @author Trudi
11   */
12  
13  public class CBJComboBox extends JComboBox
14  {
15  
16      /**
17       * Creates a JComboBox with a default data model.
18       * Sets a key selection manager.
19       */
20  
21      public CBJComboBox()
22      {
23          super();
24          setKeySelectionManager(new CBKeySelectionManager(this));
25      }
26  
27  
28      /**
29       * Creates a JComboBox that takes it's items from an existing ComboBoxModel.
30       * Sets a key selection manager.
31       */
32  
33      public CBJComboBox(ComboBoxModel aModel)
34      {
35          super(aModel);
36          setKeySelectionManager(new CBKeySelectionManager(this));
37      }
38  
39  
40      /**
41       * Creates a JComboBox that contains the elements in the specified array.
42       * Sets a key selection manager.
43       */
44  
45      public CBJComboBox(Object  [] items)
46      {
47          super(items);
48          setKeySelectionManager(new CBKeySelectionManager(this));
49      }
50  
51  
52      /**
53       * Creates a JComboBox that contains the elements in the specified Vector.
54       * Sets a key selection manager.
55       */
56  
57      public CBJComboBox(Vector   items)
58      {
59          super(items);
60          setKeySelectionManager(new CBKeySelectionManager(this));
61      }
62  
63  
64      /**
65       * Changes the default key selection manager to allow two character identification
66       * of items within the combo box.  For example if the user presses two keys within two
67       * seconds this class checks for a word beginning with the two characters that the keys
68       * represent (e.g. c+r = creatorsName).  Normally the key selection manager would jump
69       * to the first word in the list that begins with a 'c' then the first word in the list
70       * that begins with an 'r'.  This behaviour will still occur if the user presses keys that
71       * have a duration more than two seconds apart, for example, if a 'c' is pressed then three
72       * seconds later an 'r' the list would not jump to 'creatorsName' it would have jumped to
73       * the first word in the list beginning with an 'r'.
74       */
75  
76      public class CBKeySelectionManager implements KeySelectionManager
77      {
78          /**
79           * The last keystroke the user entered before the current one.
80           */
81  
82          String   oldKey = null;
83  
84          /**
85           * The position in combo box that the selection is to be moved to.
86           */
87  
88          int position = -1;
89  
90          /**
91           * The time in milliseconds of the last keystroke.
92           */
93  
94          long oldTime = -1;
95  
96          /**
97           * The combo box that this key-selection-manager is added to.
98           */
99  
100         CBJComboBox combo;
101 
102 
103         /**
104          * Constructor that does nothing more than registers the combo box that this
105          * key selection manager belongs to.
106          *
107          * @param combo the CBJComboBox that this key selection manager is added to.
108          */
109 
110         public CBKeySelectionManager(CBJComboBox combo)
111         {
112             super();
113             this.combo = combo;
114         }
115 
116 
117         /**
118          * A wrapper to selectionForKey(char aKey, ComboBoxModel aModel, long time)...just
119          * adds the time so that the manager can determine if two seconds has passed since
120          * the last key stroke.
121          *
122          * @param aKey   a char value, usually indicating a keyboard key that was pressed.
123          * @param aModel the component's data model, containing the list of selectable items.
124          * @return an int equal to the selected row, where 0 is the first item and -1 is none.
125          */
126 
127         public int selectionForKey(char aKey, ComboBoxModel aModel)
128         {
129             return selectionForKey(aKey, aModel, System.currentTimeMillis());
130         }
131 
132 
133         /**
134          * A wrapper to selectionForKey(char aKey, ComboBoxModel aModel, long time)...just
135          * adds the time so that the manager can determine if two seconds has passed since
136          * the last key stroke.
137          *
138          * @param aKey   a char value, usually indicating a keyboard key that was pressed.
139          * @param aModel the component's data model, containing the list of selectable items.
140          * @param time   the time the key stroke was pressed (actually this is not the exact time
141          *               the key was pressed but the time the selectionForKey(char aKey, ComboBoxModel aModel)
142          *               was called...'time' is just used to determine if two seconds has lapsed and if so
143          *               indicating that the 'oldKey' should be cleared.
144          * @return an int equal to the selected row, where 0 is the first item and -1 is none.
145          */
146 
147         public int selectionForKey(char aKey, ComboBoxModel aModel, long time)
148         {
149             String   key = null;      //TE: the beginning of the list item to be searched for within the list.
150 
151             if (oldTime > -1)
152             {
153                 //TE: if two seconds have passed since the last keystroke...don't
154                 //TE: keep the old key.
155                 if ((time - oldTime) > 2000)
156                     oldKey = null;
157             }
158 
159 
160             if (oldKey != null)                     //TE: if the old key has not previously been
161                 key = oldKey + String.valueOf(aKey);    //TE: assigned make the key only equal the keystroke key.
162             else                                    //TE: if the old key has previously been assigned make
163                 key = String.valueOf(aKey);         //TE: the key equal the old key + the keystroke key.
164 
165             key = key.toLowerCase();
166 
167             int count = combo.getItemCount();
168 
169             for (int i = 0; i < count; i++)
170             {
171                 //TE: iterate thru the list checking for the first list item that begins with the key.
172 
173                 Object   temp = combo.getItemAt(i);
174 
175                 if ((((String  ) temp).toLowerCase()).startsWith(key))    //TE: if there is a match...
176                 {
177 
178                     position = i;
179                     oldKey = String.valueOf(aKey);  //TE: remember the current key.
180                     oldTime = time;                 //TE: remember the current time.
181 
182                     return position;
183                 }
184             }
185 
186             oldKey = String.valueOf(aKey);          //TE: remember the current key.
187             oldTime = time;                         //TE: remember the current time.
188 
189             return position;
190         }
191     }
192 }
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