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:       sel = b.getModel();
  95:     buttons.addElement(b);
  96:   }
  97: 
  98:   /**
  99:    * Removed a given button from this group.
 100:    *
 101:    * @param b the button to remove
 102:    */
 103:   public void remove(AbstractButton b)
 104:   {
 105:     b.getModel().setGroup(null);
 106:     buttons.removeElement(b);
 107:   }
 108: 
 109:   /**
 110:    * Returns the currently added buttons.
 111:    *
 112:    * @return <code>Enumeration</code> over all added buttons
 113:    */
 114:   public Enumeration getElements()
 115:   {
 116:     return buttons.elements();
 117:   }
 118: 
 119:   /**
 120:    * Returns the currently selected button model.
 121:    *
 122:    * @return the currently selected button model, null if none was selected
 123:    *         yet
 124:    */
 125:   public ButtonModel getSelection()
 126:   {
 127:     return sel;
 128:   }
 129: 
 130:   /**
 131:    * DOCUMENT ME!
 132:    *
 133:    * @param m DOCUMENT ME!
 134:    *
 135:    * @return DOCUMENT ME!
 136:    */
 137:   AbstractButton FindButton(ButtonModel m)
 138:   {
 139:     for (int i = 0; i < buttons.size(); i++)
 140:       {
 141:     AbstractButton a = (AbstractButton) buttons.get(i);
 142:     if (a.getModel() == m)
 143:       return a;
 144:       }
 145:     return null;
 146:   }
 147: 
 148:   /**
 149:    * Sets the currently selected button model. Only one button of a group can
 150:    * be selected at a time.
 151:    *
 152:    * @param m the model to select
 153:    * @param b true if this button is to be selected, false otherwise
 154:    */
 155:   public void setSelected(ButtonModel m, boolean b)
 156:   {
 157:     if ((sel != m || b) && (! b || sel == m))
 158:       return;
 159: 
 160:     if (b && sel != m)
 161:       {
 162:         ButtonModel old = sel;
 163:         sel = m;
 164:         
 165:         if (old != null)
 166:           old.setSelected(false);
 167:         AbstractButton button = FindButton(old);
 168:         if (button != null)
 169:           button.repaint();
 170:       }
 171:     else if (!b && sel == m)
 172:       m.setSelected(true);
 173:   }
 174: 
 175:   /**
 176:    * Checks if the given <code>ButtonModel</code> is selected in this button
 177:    * group.
 178:    *
 179:    * @param m DOCUMENT ME!
 180:    *
 181:    * @return true of given <code>ButtonModel</code> is selected, false
 182:    *         otherwise
 183:    */
 184:   public boolean isSelected(ButtonModel m)
 185:   {
 186:     return m == sel;
 187:   }
 188: 
 189:   /**
 190:    * Return the number of buttons in this button group.
 191:    *
 192:    * @return the number of buttons
 193:    *
 194:    * @since 1.3
 195:    */
 196:   public int getButtonCount()
 197:   {
 198:     return buttons.size();
 199:   }
 200: }