odk/examples/DevelopersGuide/Accessibility/MessageArea.java

   1 /*************************************************************************
   2  *
   3  *  $RCSfile: MessageArea.java,v $
   4  *
   5  *  $Revision: 1.3 $
   6  *
   7  *  last change: $Author: hr $ $Date: 2003-06-30 15:06:53 $
   8  *
   9  *  The Contents of this file are made available subject to the terms of
  10  *  the BSD license.
  11  *
  12  *  Copyright (c) 2003 by Sun Microsystems, Inc.
  13  *  All rights reserved.
  14  *
  15  *  Redistribution and use in source and binary forms, with or without
  16  *  modification, are permitted provided that the following conditions
  17  *  are met:
  18  *  1. Redistributions of source code must retain the above copyright
  19  *     notice, this list of conditions and the following disclaimer.
  20  *  2. Redistributions in binary form must reproduce the above copyright
  21  *     notice, this list of conditions and the following disclaimer in the
  22  *     documentation and/or other materials provided with the distribution.
  23  *  3. Neither the name of Sun Microsystems, Inc. nor the names of its
  24  *     contributors may be used to endorse or promote products derived
  25  *     from this software without specific prior written permission.
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  27  *  THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
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  30  *  FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
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  37  *  USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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  39  *************************************************************************/
  40
  41 import java.awt.Font;
  42 import java.awt.Rectangle;
  43 import java.awt.Color;
  44 import java.awt.Graphics;
  45 import javax.swing.JScrollPane;
  46 import javax.swing.JTextArea;
  47 import javax.swing.JScrollBar;
  48
  49
  50
  51 /** A message area displays text in a scrollable text widget.  It is a
  52     singleton.  Other objects can access it directly to display messages.
  53 */
  54 public class MessageArea
  55     extends JScrollPane
  56 {
  57     public static synchronized MessageArea Instance ()
  58     {
  59         if (saInstance == null)
  60             saInstance = new MessageArea ();
  61         return saInstance;
  62     }
  63
  64
  65
  66
  67     /** Create a new message area.  This method is private because the class is
  68         a singleton and may therefore not be instanciated from the outside.
  69     */
  70     private MessageArea ()
  71     {
  72         maText = new JTextArea();
  73         maText.setBackground (new Color (255,250,240));
  74         maText.setFont (new Font ("Helvetica", Font.PLAIN, 9));
  75         setViewportView (maText);
  76         setVerticalScrollBarPolicy (JScrollPane.VERTICAL_SCROLLBAR_ALWAYS);
  77         setHorizontalScrollBarPolicy (JScrollPane.HORIZONTAL_SCROLLBAR_ALWAYS);
  78
  79         printMessage (
  80             "class path is " + System.getProperty ("java.class.path") + "\n");
  81     }
  82
  83
  84
  85
  86     /** Show the given string at the end of the message area and scroll to make
  87         it visible.
  88     */
  89     public static synchronized void print (String aMessage)
  90     {
  91         Instance().printMessage(aMessage);
  92     }
  93
  94
  95
  96
  97     /** Show the given string at the end of the message area and scroll to make
  98         it visible.
  99     */
 100     public static void println (String aMessage)
 101     {
 102         Instance().printMessage (aMessage+"\n");
 103     }
 104
 105
 106     public void paintComponent (Graphics g)
 107     {
 108         // Synchronize with the graphics object to prevent paint problems.
 109         // Remember that this is not done by Swing itself.
 110         synchronized (g)
 111         {
 112             JScrollBar sb = getVerticalScrollBar();
 113             if (sb != null)
 114             {
 115                 int nScrollBarValue = sb.getMaximum() - sb.getVisibleAmount() - 1;
 116                 sb.setValue (nScrollBarValue);
 117             }
 118             super.paintComponent (g);
 119         }
 120     }
 121
 122
 123
 124
 125     /** Append the given string to the end of the text and scroll so that it
 126         becomes visible.  This is an internal method.  Use one of the static
 127         and public ones.
 128     */
 129     private synchronized void printMessage (String aMessage)
 130     {
 131         maText.append (aMessage);
 132     }
 133
 134
 135
 136
 137     private static MessageArea saInstance = null;
 138     private JTextArea maText;
 139 }