001    /* DefaultSingleSelectionModel.java --
002       Copyright (C) 2002, 2004, 2006,  Free Software Foundation, Inc.
003    
004    This file is part of GNU Classpath.
005    
006    GNU Classpath is free software; you can redistribute it and/or modify
007    it under the terms of the GNU General Public License as published by
008    the Free Software Foundation; either version 2, or (at your option)
009    any later version.
010    
011    GNU Classpath is distributed in the hope that it will be useful, but
012    WITHOUT ANY WARRANTY; without even the implied warranty of
013    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
014    General Public License for more details.
015    
016    You should have received a copy of the GNU General Public License
017    along with GNU Classpath; see the file COPYING.  If not, write to the
018    Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
019    02110-1301 USA.
020    
021    Linking this library statically or dynamically with other modules is
022    making a combined work based on this library.  Thus, the terms and
023    conditions of the GNU General Public License cover the whole
024    combination.
025    
026    As a special exception, the copyright holders of this library give you
027    permission to link this library with independent modules to produce an
028    executable, regardless of the license terms of these independent
029    modules, and to copy and distribute the resulting executable under
030    terms of your choice, provided that you also meet, for each linked
031    independent module, the terms and conditions of the license of that
032    module.  An independent module is a module which is not derived from
033    or based on this library.  If you modify this library, you may extend
034    this exception to your version of the library, but you are not
035    obligated to do so.  If you do not wish to do so, delete this
036    exception statement from your version. */
037    
038    
039    package javax.swing;
040    
041    import java.io.Serializable;
042    import java.util.EventListener;
043    
044    import javax.swing.event.ChangeEvent;
045    import javax.swing.event.ChangeListener;
046    import javax.swing.event.EventListenerList;
047    
048    /**
049     * The default implementation of {@link SingleSelectionModel}, used in
050     * {@link JTabbedPane}, {@link JMenuBar} and {@link JPopupMenu}.
051     *
052     * @author Andrew Selkirk
053     */
054    public class DefaultSingleSelectionModel
055      implements SingleSelectionModel, Serializable
056    {
057      private static final long serialVersionUID = 3676229404753786004L;
058    
059      /**
060       * changeEvent
061       */
062      protected transient ChangeEvent changeEvent;
063    
064      /**
065       * listenerList
066       */
067      protected EventListenerList listenerList = new EventListenerList();
068    
069      /**
070       * The selected index (or -1 for no selection).
071       */
072      private int index = -1;
073    
074      /**
075       * Creates a new <code>DefaultSingleSelectionModel</code> with no current
076       * selection.
077       */
078      public DefaultSingleSelectionModel()
079      {
080        // Do nothing.
081      }
082    
083      /**
084       * Returns the selected index or <code>-1</code> if there is no selection.
085       * 
086       * @return The selected index.
087       * 
088       * @see #setSelectedIndex(int)
089       */
090      public int getSelectedIndex()
091      {
092        return index;
093      }
094    
095      /**
096       * Sets the selected index and, if this is different to the previous 
097       * selection, sends a {@link ChangeEvent} to all registered listeners.
098       * 
099       * @param index  the index (use <code>-1</code> to represent no selection).
100       * 
101       * @see #getSelectedIndex()
102       * @see #clearSelection
103       */
104      public void setSelectedIndex(int index)
105      {
106        if (this.index != index)
107          {
108            this.index = index;
109            fireStateChanged();
110          }
111      }
112    
113      /**
114       * Clears the selection by setting the selected index to <code>-1</code> and
115       * sends a {@link ChangeEvent} to all registered listeners.  If the selected
116       * index is already <code>-1</code>, this method does nothing.  
117       */
118      public void clearSelection()
119      {
120        setSelectedIndex(-1);
121      }
122    
123      /**
124       * Returns <code>true</code> if there is a selection, and <code>false</code>
125       * otherwise.  
126       * 
127       * @return A boolean.
128       */
129      public boolean isSelected()
130      {
131        return index != -1;
132      }
133    
134      /**
135       * Registers a listener to receive {@link ChangeEvent} notifications from
136       * this model whenever the selected index changes.
137       *
138       * @param listener the listener to add.
139       */
140      public void addChangeListener(ChangeListener listener)
141      {
142        listenerList.add(ChangeListener.class, listener);
143      }
144    
145      /**
146       * Deregisters a listener so that it no longer receives {@link ChangeEvent}
147       * notifications from this model.
148       *
149       * @param listener the listener to remove.
150       */
151      public void removeChangeListener(ChangeListener listener)
152      {
153        listenerList.remove(ChangeListener.class, listener);
154      }
155    
156      /**
157       * fireStateChanged
158       */
159      protected void fireStateChanged()
160      {
161        if (changeEvent == null)
162          changeEvent = new ChangeEvent(this);
163        ChangeListener[] listeners = getChangeListeners();
164        for (int i = 0; i < listeners.length; i++)
165          listeners[i].stateChanged(changeEvent);
166      }
167    
168      /**
169       * getListeners
170       *
171       * @param listenerClass the type fo listener
172       *
173       * @return an array of listeners
174       *
175       * @since 1.3
176       */
177      public <T extends EventListener> T[] getListeners(Class<T> listenerClass)
178      {
179        return listenerList.getListeners(listenerClass);
180      }
181    
182      /**
183       * getChangeListeners
184       *
185       * @since 1.4
186       */
187      public ChangeListener[] getChangeListeners()
188      {
189        return (ChangeListener[]) getListeners(ChangeListener.class);
190      }
191    }