libjava/java/awt/Label.java

   1 /* Label.java -- Java label widget
   2    Copyright (C) 1999, 2000, 2002, 2004, 2005  Free Software Foundation, Inc.
   3
   4 This file is part of GNU Classpath.
   5
   6 GNU Classpath is free software; you can redistribute it and/or modify
   7 it under the terms of the GNU General Public License as published by
   8 the Free Software Foundation; either version 2, or (at your option)
   9 any later version.
  10
  11 GNU Classpath is distributed in the hope that it will be useful, but
  12 WITHOUT ANY WARRANTY; without even the implied warranty of
  13 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  14 General Public License for more details.
  15
  16 You should have received a copy of the GNU General Public License
  17 along with GNU Classpath; see the file COPYING.  If not, write to the
  18 Free Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
  19 02111-1307 USA.
  20
  21 Linking this library statically or dynamically with other modules is
  22 making a combined work based on this library.  Thus, the terms and
  23 conditions of the GNU General Public License cover the whole
  24 combination.
  25
  26 As a special exception, the copyright holders of this library give you
  27 permission to link this library with independent modules to produce an
  28 executable, regardless of the license terms of these independent
  29 modules, and to copy and distribute the resulting executable under
  30 terms of your choice, provided that you also meet, for each linked
  31 independent module, the terms and conditions of the license of that
  32 module.  An independent module is a module which is not derived from
  33 or based on this library.  If you modify this library, you may extend
  34 this exception to your version of the library, but you are not
  35 obligated to do so.  If you do not wish to do so, delete this
  36 exception statement from your version. */
  37
  38
  39 package java.awt;
  40
  41 import java.awt.peer.LabelPeer;
  42
  43 import javax.accessibility.Accessible;
  44 import javax.accessibility.AccessibleContext;
  45 import javax.accessibility.AccessibleRole;
  46
  47 /**
  48   * This component is used for displaying simple text strings that cannot
  49   * be edited by the user.
  50   *
  51   * @author Aaron M. Renn (arenn@urbanophile.com)
  52   * @author Tom Tromey (tromey@cygnus.com)
  53   * @author Andrew John Hughes  (gnu_andrew@member.fsf.org)
  54   */
  55 public class Label extends Component implements Accessible
  56 {
  57
  58 /*
  59  * Static Variables
  60  */
  61
  62 /**
  63   * Alignment constant aligning the text to the left of its window.
  64   */
  65 public static final int LEFT = 0;
  66
  67 /**
  68   * Alignment constant aligning the text in the center of its window.
  69   */
  70 public static final int CENTER = 1;
  71
  72 /**
  73   * Alignment constant aligning the text to the right of its window.
  74   */
  75 public static final int RIGHT = 2;
  76
  77 // Serialization version constant:
  78 private static final long serialVersionUID = 3094126758329070636L;
  79
  80 /*************************************************************************/
  81
  82 /*
  83  * Instance Variables
  84  */
  85
  86 /**
  87   * @serial Indicates the alignment of the text within this label's window.
  88   * This is one of the constants in this class.  The default value is
  89   * <code>LEFT</code>.
  90   */
  91 private int alignment;
  92
  93 /**
  94   * @serial The text displayed in the label
  95   */
  96 private String text;
  97
  98 /*************************************************************************/
  99
 100 /*
 101  * Constructors
 102  */
 103
 104 /**
 105   * Initializes a new instance of <code>Label</code> with no text.
 106   *
 107   * @exception HeadlessException If GraphicsEnvironment.isHeadless() is true.
 108   */
 109 public
 110 Label()
 111 {
 112   this("", LEFT);
 113 }
 114
 115 /*************************************************************************/
 116
 117 /**
 118   * Initializes a new instance of <code>Label</code> with the specified
 119   * text that is aligned to the left.
 120   *
 121   * @param text The text of the label.
 122   *
 123   * @exception HeadlessException If GraphicsEnvironment.isHeadless() is true.
 124   */
 125 public
 126 Label(String text)
 127 {
 128   this(text, LEFT);
 129 }
 130
 131 /*************************************************************************/
 132
 133 /**
 134   * Initializes a new instance of <code>Label</code> with the specified
 135   * text and alignment.
 136   *
 137   * @param text The text of the label.
 138   * @param alignment The desired alignment for the text in this label,
 139   * which must be one of <code>LEFT</code>, <code>CENTER</code>, or
 140   * <code>RIGHT</code>.
 141   *
 142   * @exception HeadlessException If GraphicsEnvironment.isHeadless() is true.
 143   */
 144 public
 145 Label(String text, int alignment)
 146 {
 147   setAlignment (alignment);
 148   setText (text);
 149
 150   if (GraphicsEnvironment.isHeadless())
 151     throw new HeadlessException ();
 152 }
 153
 154 /*************************************************************************/
 155
 156 /*
 157  * Instance Variables
 158  */
 159
 160 /**
 161   * Returns the constant indicating the alignment of the text in this
 162   * label.  The value returned will be one of the alignment constants
 163   * from this class.
 164   *
 165   * @return The alignment of the text in the label.
 166   */
 167 public int
 168 getAlignment()
 169 {
 170   return(alignment);
 171 }
 172
 173 /*************************************************************************/
 174
 175 /**
 176   * Sets the text alignment of this label to the specified value.
 177   *
 178   * @param alignment The desired alignment for the text in this label,
 179   * which must be one of <code>LEFT</code>, <code>CENTER</code>, or
 180   * <code>RIGHT</code>.
 181   */
 182 public synchronized void
 183 setAlignment(int alignment)
 184 {
 185   if (alignment != CENTER && alignment != LEFT && alignment != RIGHT)
 186     throw new IllegalArgumentException ("invalid alignment: " + alignment);
 187   this.alignment = alignment;
 188   if (peer != null)
 189     {
 190       LabelPeer lp = (LabelPeer) peer;
 191       lp.setAlignment (alignment);
 192     }
 193 }
 194
 195 /*************************************************************************/
 196
 197 /**
 198   * Returns the text displayed in this label.
 199   *
 200   * @return The text for this label.
 201   */
 202 public String
 203 getText()
 204 {
 205   return(text);
 206 }
 207
 208 /*************************************************************************/
 209
 210 /**
 211   * Sets the text in this label to the specified value.
 212   *
 213   * @param text The new text for this label.
 214   */
 215 public synchronized void
 216 setText(String text)
 217 {
 218   this.text = text;
 219
 220   if (peer != null)
 221     {
 222       LabelPeer lp = (LabelPeer) peer;
 223       lp.setText (text);
 224     }
 225 }
 226
 227 /*************************************************************************/
 228
 229 /**
 230   * Notifies this label that it has been added to a container, causing
 231   * the peer to be created.  This method is called internally by the AWT
 232   * system.
 233   */
 234 public void
 235 addNotify()
 236 {
 237   if (peer == null)
 238     peer = getToolkit ().createLabel (this);
 239   super.addNotify ();
 240 }
 241
 242 /*************************************************************************/
 243
 244 /**
 245   * Returns a parameter string useful for debugging.
 246   *
 247   * @return A debugging string.
 248   */
 249 protected String
 250 paramString()
 251 {
 252   return ("text=" + getText() + ",alignment=" +
 253           getAlignment() + "," + super.paramString());
 254 }
 255
 256 /**
 257  * This class provides accessibility support for the label.
 258  */
 259 protected class AccessibleAWTLabel
 260   extends AccessibleAWTComponent
 261 {
 262   /**
 263    * For compatability with Sun's JDK 1.4.2 rev. 5
 264    */
 265   private static final long serialVersionUID = -3568967560160480438L;
 266
 267   /**
 268    * Constructor for the accessible label.
 269    */
 270   public AccessibleAWTLabel()
 271   {
 272   }
 273
 274   /**
 275    * Returns the accessible name for the label.  This is
 276    * the text used in the label.
 277    *
 278    * @return a <code>String</code> containing the accessible
 279    *         name for this label.
 280    */
 281   public String getAccessibleName()
 282   {
 283     return getText();
 284   }
 285
 286   /**
 287    * Returns the accessible role for the label.
 288    *
 289    * @return an instance of <code>AccessibleRole</code>, describing
 290    *         the role of the label.
 291    */
 292   public AccessibleRole getAccessibleRole()
 293   {
 294     return AccessibleRole.LABEL;
 295   }
 296
 297 }
 298
 299 /**
 300  * Gets the AccessibleContext associated with this <code>Label</code>.
 301  * The context is created, if necessary.
 302  *
 303  * @return the associated context
 304  */
 305 public AccessibleContext getAccessibleContext()
 306 {
 307   /* Create the context if this is the first request */
 308   if (accessibleContext == null)
 309     accessibleContext = new AccessibleAWTLabel();
 310   return accessibleContext;
 311 }
 312
 313 } // class Label
 314