Source for javax.swing.ButtonGroup

   1: /* ButtonGroup.java --
   2:    Copyright (C) 2002 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:   /** DOCUMENT ME! */
  69:   private static final long serialVersionUID = 4259076101881721375L;
  70: 
  71:   /** The buttons added to this button group. */
  72:   protected Vector buttons = new Vector();
  73: 
  74:   /** The currently selected button model. */
  75:   ButtonModel sel;
  76: 
  77:   /**
  78:    * Creates a new button group.
  79:    */
  80:   public ButtonGroup()
  81:   {
  82:     // Nothing to do here.
  83:   }
  84: 
  85:   /**
  86:    * Adds a button to this group.
  87:    *
  88:    * @param b the button to add
  89:    */
  90:   public void add(AbstractButton b)
  91:   {
  92:     b.getModel().setGroup(this);
  93:     if (b.isSelected())
  94:       {
  95:         if (sel == null)
  96:           sel = b.getModel();
  97:         else
  98:           b.setSelected(false);
  99:       }    buttons.addElement(b);
 100:   }
 101: 
 102:   /**
 103:    * Removed a given button from this group.
 104:    *
 105:    * @param b the button to remove
 106:    */
 107:   public void remove(AbstractButton b)
 108:   {
 109:     b.getModel().setGroup(null);
 110:     buttons.removeElement(b);
 111:   }
 112: 
 113:   /**
 114:    * Returns the currently added buttons.
 115:    *
 116:    * @return <code>Enumeration</code> over all added buttons
 117:    */
 118:   public Enumeration getElements()
 119:   {
 120:     return buttons.elements();
 121:   }
 122: 
 123:   /**
 124:    * Returns the currently selected button model.
 125:    *
 126:    * @return the currently selected button model, null if none was selected
 127:    *         yet
 128:    */
 129:   public ButtonModel getSelection()
 130:   {
 131:     return sel;
 132:   }
 133: 
 134:   /**
 135:    * DOCUMENT ME!
 136:    *
 137:    * @param m DOCUMENT ME!
 138:    *
 139:    * @return DOCUMENT ME!
 140:    */
 141:   AbstractButton FindButton(ButtonModel m)
 142:   {
 143:     for (int i = 0; i < buttons.size(); i++)
 144:       {
 145:     AbstractButton a = (AbstractButton) buttons.get(i);
 146:     if (a.getModel() == m)
 147:       return a;
 148:       }
 149:     return null;
 150:   }
 151: 
 152:   /**
 153:    * Sets the currently selected button model. Only one button of a group can
 154:    * be selected at a time.
 155:    *
 156:    * @param m the model to select
 157:    * @param b true if this button is to be selected, false otherwise
 158:    */
 159:   public void setSelected(ButtonModel m, boolean b)
 160:   {
 161:     if ((sel != m || b) && (! b || sel == m))
 162:       return;
 163: 
 164:     if (b && sel != m)
 165:       {
 166:         ButtonModel old = sel;
 167:         sel = m;
 168:         
 169:         if (old != null)
 170:           old.setSelected(false);
 171:         AbstractButton button = FindButton(old);
 172:         if (button != null)
 173:           button.repaint();
 174:       }
 175:     else if (!b && sel == m)
 176:       m.setSelected(true);
 177:   }
 178: 
 179:   /**
 180:    * Checks if the given <code>ButtonModel</code> is selected in this button
 181:    * group.
 182:    *
 183:    * @param m DOCUMENT ME!
 184:    *
 185:    * @return true of given <code>ButtonModel</code> is selected, false
 186:    *         otherwise
 187:    */
 188:   public boolean isSelected(ButtonModel m)
 189:   {
 190:     return m == sel;
 191:   }
 192: 
 193:   /**
 194:    * Return the number of buttons in this button group.
 195:    *
 196:    * @return the number of buttons
 197:    *
 198:    * @since 1.3
 199:    */
 200:   public int getButtonCount()
 201:   {
 202:     return buttons.size();
 203:   }
 204: }