libjava/classpath/javax/swing/SpinnerListModel.java

   1 /* SpinnerListModel.java -- A spinner model backed by a list or an array.
   2    Copyright (C) 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., 51 Franklin Street, Fifth Floor, Boston, MA
  19 02110-1301 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 package javax.swing;
  39
  40 import java.io.Serializable;
  41 import java.util.ArrayList;
  42 import java.util.Arrays;
  43 import java.util.List;
  44
  45 import javax.swing.event.ChangeEvent;
  46
  47 /**
  48  * An implementation of <code>SpinnerModel</code> which uses the values
  49  * contained within a list or an array.  The backing list or array is
  50  * only stored as a reference within the class.  As a result, changes
  51  * made elsewhere to the members of the list or array are reflected by
  52  * this model.
  53  * <p>
  54  *
  55  * The model itself inherits a list of <code>ChangeListener</code>s from
  56  * <code>AbstractSpinnerModel</code>.  As this code is unaware of changes
  57  * made to the backing list or array, it is the responsibility of the
  58  * application using the model to invoke <code>fireStateChanged()</code>,
  59  * in order to notify any <code>ChangeListener</code>s, when the list or array
  60  * changes.  The model handles notification when the reference itself
  61  * is changed via <code>setList()</code> or when the current value is
  62  * set directly using <code>setValue()</code>.
  63  *
  64  * @author Andrew John Hughes (gnu_andrew@member.fsf.org)
  65  * @see SpinnerModel
  66  * @see AbstractSpinnerModel
  67  * @see JSpinner
  68  * @since 1.4
  69  */
  70
  71 public class SpinnerListModel extends AbstractSpinnerModel
  72   implements Serializable
  73 {
  74   /**
  75    * For compatability with Sun's JDK
  76    */
  77   private static final long serialVersionUID = 3358804052191994516L;
  78
  79   /**
  80    * The backing list for this model.
  81    */
  82   private List list;
  83
  84   /**
  85    * The current index in the list.
  86    */
  87   private transient int index;
  88
  89   /**
  90    * Constructs a default <code>SpinnerListModel</code>.  This
  91    * is a model backed by a list containing only the single
  92    * <code>String</code> element, "empty".
  93    */
  94   public SpinnerListModel()
  95   {
  96     List defaultList;
  97
  98     // Create an empty list.
  99     defaultList = new ArrayList();
 100     // Add the string "empty".
 101     defaultList.add("empty");
 102     // Set the list.
 103     setList(defaultList);
 104   }
 105
 106   /**
 107    * Constructs a <code>SpinnerListModel</code> using the supplied list.
 108    * The model maintains a reference to this list, and returns
 109    * consecutive elements in response to calls to <code>getNextValue()</code>.
 110    * The initial value is that at position 0, so an initial call
 111    * to <code>getValue()</code> returns the same as <code>list.get(0)</code>.
 112    *
 113    * @param list The list to use for this model.
 114    *
 115    * @throws IllegalArgumentException if the list is null or contains no
 116    *         elements.
 117    *
 118    * @see SpinnerListModel#getNextValue()
 119    * @see SpinnerListModel#getValue()
 120    */
 121   public SpinnerListModel(List list)
 122   {
 123     // Retain a reference to the valid list.
 124     setList(list);
 125   }
 126
 127   /**
 128    * Constructs a <code>SpinnerListModel</code> using the supplied array.
 129    * The model stores a reference to the wrapper list returned by
 130    * <code>Arrays.asList()</code>.  The wrapper list reflects modifications
 131    * in the underlying array, so these changes will also be reflected
 132    * by the model.  The model produces consecutive elements from the array
 133    * in response to calls to <code>getNextValue()</code>.  The initial
 134    * value returned by <code>getValue()</code> is the same as
 135    * <code>array[0]</code>.
 136    *
 137    * @param array The array to use for this model.
 138    *
 139    * @throws IllegalArgumentException if the array is null or contains
 140    *         no elements.
 141    *
 142    * @see Arrays#asList(Object[])
 143    * @see SpinnerListModel#getNextValue()
 144    * @see SpinnerListModel#getValue()
 145    */
 146   public SpinnerListModel(Object[] array)
 147   {
 148     // Check for a null or zero-sized array.
 149     if (array == null || array.length == 0)
 150       {
 151         throw new IllegalArgumentException("The supplied array was invalid.");
 152       }
 153
 154         // Retain a reference to a wrapper around the valid array.
 155         // The array, in list form, will be tested again here, but we can't really
 156         // avoid this -- a null value to Arrays.asList will throw a
 157     // NullPointerException.
 158     setList(Arrays.asList(array));
 159   }
 160
 161   /**
 162    * Returns the backing list for this model.
 163    *
 164    * @return The backing list.
 165    */
 166   public List getList()
 167   {
 168     return list;
 169   }
 170
 171   /**
 172    * Returns the next value from the list, which is the same as the element
 173    * stored at the current index + 1.  Null is returned if there are no more
 174    * values to be returned (the end of the list has been reached).  An
 175    * ambiguity can occur here, as null may also be returned as a valid list
 176    * element.  This operation does not change the current value.
 177    *
 178    * @return The next value from the list or null.
 179    */
 180   public Object getNextValue()
 181   {
 182     // Check for a next value.
 183     if (index < (list.size() - 1))
 184       // Return the element at the next index.
 185       return list.get(index + 1);
 186     else
 187       // Return null as this is the end of the list.
 188       return null;
 189     }
 190
 191   /**
 192    * Returns the previous value from the list, which is the same as the element
 193    * stored at the current index - 1.  Null is returned if there are no more
 194    * values to be returned (the start of the list has been reached).  An
 195    * ambiguity can occur here, as null may also be returned as a valid list
 196    * element.  This operation does not change the current value.
 197    *
 198    * @return The previous value from the list or null.
 199    */
 200   public Object getPreviousValue()
 201   {
 202     // Check for a previous value.
 203     if (index > 0)
 204       // Return the element at the previous position.
 205       return list.get(index - 1);
 206         else
 207       // Return null as this is the start of the list.
 208       return null;
 209     }
 210
 211   /**
 212    * Returns the current value of the model.  Initially, this will
 213    * be the element at position 0.  On later invocations, this will
 214    * be the last element returned by <code>getNextValue()</code>
 215    * or <code>getPreviousValue()</code>.
 216    *
 217    * @return The current value.
 218    *
 219    * @see SpinnerListModel#getPreviousValue()
 220    * @see SpinnerListModel#getNextValue()
 221    */
 222   public Object getValue()
 223   {
 224     return list.get(index);
 225   }
 226
 227   /**
 228    * Changes the backing list for this model.  The model only stores
 229    * a reference to the list, so any changes made to the list elsewhere
 230    * will be reflected in the values returned by the model.  A
 231    * <code>ChangeEvent</code> is fired if the list being used actually
 232    * changes (i.e. the new list is not referentially equal (!=) to the
 233    * old one).
 234    *
 235    * @param list The new list to use.
 236    *
 237    * @throws IllegalArgumentException if the list is null or contains
 238    *         no elements.
 239    *
 240    * @see ChangeEvent
 241    */
 242   public void setList(List list)
 243   {
 244     // Check for null or zero size list.
 245     if (list == null || list.size() == 0)
 246       throw new IllegalArgumentException("The supplied list was invalid.");
 247
 248     // Check for a change of referenced list.
 249     if (this.list != list)
 250       {
 251         // Store the new list.
 252         this.list = list;
 253         // Notify listeners of a change.
 254         fireStateChanged();
 255       }
 256     // We reset the other values in either case.
 257     // Set the index to 0.
 258     index = 0;
 259   }
 260
 261   /**
 262    * Sets the current value of the model to be the one supplied.
 263    * The value must exist within the backing list in order for
 264    * the change to take place.  Otherwise, an exception is thrown.
 265    * The value used is the first occurrence of the value within
 266    * the backing list.  Listeners are notified of this change.
 267    * Following the change, <code>getNextValue()</code> and
 268    * <code>getPreviousValue()</code> return the objects following
 269    * and prior to the supplied value, respectively.
 270    *
 271    * @param value The requested new value of the list.
 272    *
 273    * @throws IllegalArgumentException if the supplied value does
 274    *         not exist in the backing list.
 275    *
 276    * @see SpinnerListModel#getPreviousValue()
 277    * @see SpinnerListModel#getNextValue()
 278    */
 279   public void setValue(Object value)
 280   {
 281     int valueIndex;
 282
 283     // Search for the value in the list.
 284     valueIndex = list.indexOf(value);
 285     // Check for the value being found.
 286     if (valueIndex == -1)
 287       throw new IllegalArgumentException("The supplied value does not "
 288                                          + "exist in this list");
 289     // Make the indices match.
 290     index = valueIndex;
 291     // Notify the listeners.
 292     fireStateChanged();
 293   }
 294
 295 }