Source for javax.swing.ButtonGroup

   1: /* ButtonGroup.java --
   2:    Copyright (C) 2002, 2006, 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.Enumeration;
  42: import java.util.Vector;
  43: 
  44: 
  45: /**
  46:  * Logically groups a set of buttons, so that only one of the buttons in
  47:  * a <code>ButtonGroup</code> can be selected at the same time. If one
  48:  * button in a <code>ButtonGroup</code> is selected, all other buttons
  49:  * are automatically deselected.
  50:  *
  51:  * While <code>ButtonGroup</code> can be used for all buttons that are derived
  52:  * from {@link AbstractButton}, it is normally only used for
  53:  * {@link JRadioButton}s, {@link JRadioButtonMenuItem}s and
  54:  * {@link JToggleButton}s.
  55:  *
  56:  * You could use it for {@link JCheckBox}es, but for the sake of usability
  57:  * this is strongly discouraged because the common expectation of checkboxes
  58:  * is that the user is allowed to make multiple selections.
  59:  *
  60:  * It makes no sense to put {@link JButton}s or {@link JMenuItem}s in
  61:  * a <code>ButtonGroup</code> because they don't implement the
  62:  * <code>selected</code> semantics.
  63:  *
  64:  * @author original author unknown
  65:  */
  66: public class ButtonGroup implements Serializable
  67: {
  68:   private static final long serialVersionUID = 4259076101881721375L;
  69: 
  70:   /** Stores references to the buttons added to this button group. */
  71:   protected Vector<AbstractButton> buttons = new Vector<AbstractButton>();
  72: 
  73:   /** The currently selected button model. */
  74:   ButtonModel sel;
  75: 
  76:   /**
  77:    * Creates a new button group.
  78:    */
  79:   public ButtonGroup()
  80:   {
  81:     // Nothing to do here.
  82:   }
  83: 
  84:   /**
  85:    * Adds a button to this group.  If the button is in the selected state, then:
  86:    * <ul>
  87:    *   <li>if the group has no current selection, the new button becomes the 
  88:    *     selected button for the group;</li>
  89:    *   <li>if the group already has a selected button, the new button is set to
  90:    *     "not selected".</li>
  91:    * </ul>
  92:    *
  93:    * @param b the button to add (<code>null</code> is ignored).
  94:    */
  95:   public void add(AbstractButton b)
  96:   {
  97:     if (b == null)
  98:       return;
  99:     b.getModel().setGroup(this);
 100:     if (b.isSelected())
 101:       {
 102:         if (sel == null)
 103:           sel = b.getModel();
 104:         else
 105:           b.setSelected(false);
 106:       }    
 107:     buttons.addElement(b);
 108:   }
 109: 
 110:   /**
 111:    * Removes the specified button from this group.  If the button is the 
 112:    * selected button, the current selection is set to <code>null</code>.  
 113:    * The group for the removed button's model is set to <code>null</code>.  
 114:    *
 115:    * @param b the button to remove (<code>null</code> is ignored).
 116:    */
 117:   public void remove(AbstractButton b)
 118:   {
 119:     if (b == null)
 120:       return;
 121:     b.getModel().setGroup(null);
 122:     if (b.getModel() == sel)
 123:       sel = null;
 124:     buttons.removeElement(b);
 125:   }
 126: 
 127:   /**
 128:    * Returns the currently added buttons.
 129:    *
 130:    * @return <code>Enumeration</code> over all added buttons
 131:    */
 132:   public Enumeration<AbstractButton> getElements()
 133:   {
 134:     return buttons.elements();
 135:   }
 136: 
 137:   /**
 138:    * Returns the currently selected button model.
 139:    *
 140:    * @return the currently selected button model, null if none was selected
 141:    *         yet
 142:    */
 143:   public ButtonModel getSelection()
 144:   {
 145:     return sel;
 146:   }
 147: 
 148:   /**
 149:    * Returns the button that has the specified model, or <code>null</code> if
 150:    * there is no such button in the group.
 151:    *
 152:    * @param m  the button model.
 153:    *
 154:    * @return The button that has the specified model, or <code>null</code>.
 155:    */
 156:   AbstractButton findButton(ButtonModel m)
 157:   {
 158:     for (int i = 0; i < buttons.size(); i++)
 159:       {
 160:         AbstractButton a = (AbstractButton) buttons.get(i);
 161:         if (a.getModel() == m)
 162:           return a;
 163:       }
 164:     return null;
 165:   }
 166: 
 167:   /**
 168:    * Sets the currently selected button model. Only one button of a group can
 169:    * be selected at a time.
 170:    *
 171:    * @param m the model to select
 172:    * @param b true if this button is to be selected, false otherwise
 173:    */
 174:   public void setSelected(ButtonModel m, boolean b)
 175:   {
 176:     if ((sel != m || b) && (! b || sel == m))
 177:       return;
 178: 
 179:     if (b && sel != m)
 180:       {
 181:         ButtonModel old = sel;
 182:         sel = m;
 183:         
 184:         if (old != null)
 185:           old.setSelected(false);
 186:         
 187:         if (m != null)
 188:           sel.setSelected(true);
 189:         
 190:         AbstractButton button = findButton(old);
 191:         if (button != null)
 192:           button.repaint();
 193:       }
 194:     else if (!b && sel == m)
 195:       m.setSelected(true);
 196:   }
 197: 
 198:   /**
 199:    * Checks if the given <code>ButtonModel</code> is selected in this button
 200:    * group.
 201:    *
 202:    * @param m  the button model (<code>null</code> permitted).
 203:    *
 204:    * @return <code>true</code> if <code>m</code> is the selected button model
 205:    *     in this group, and <code>false</code> otherwise.
 206:    */
 207:   public boolean isSelected(ButtonModel m)
 208:   {
 209:     return m == sel;
 210:   }
 211: 
 212:   /**
 213:    * Return the number of buttons in this button group.
 214:    *
 215:    * @return the number of buttons
 216:    *
 217:    * @since 1.3
 218:    */
 219:   public int getButtonCount()
 220:   {
 221:     return buttons.size();
 222:   }
 223: }