001 /* ButtonGroup.java --
002 Copyright (C) 2002, 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 package javax.swing;
039
040 import java.io.Serializable;
041 import java.util.Enumeration;
042 import java.util.Vector;
043
044
045 /**
046 * Logically groups a set of buttons, so that only one of the buttons in
047 * a <code>ButtonGroup</code> can be selected at the same time. If one
048 * button in a <code>ButtonGroup</code> is selected, all other buttons
049 * are automatically deselected.
050 *
051 * While <code>ButtonGroup</code> can be used for all buttons that are derived
052 * from {@link AbstractButton}, it is normally only used for
053 * {@link JRadioButton}s, {@link JRadioButtonMenuItem}s and
054 * {@link JToggleButton}s.
055 *
056 * You could use it for {@link JCheckBox}es, but for the sake of usability
057 * this is strongly discouraged because the common expectation of checkboxes
058 * is that the user is allowed to make multiple selections.
059 *
060 * It makes no sense to put {@link JButton}s or {@link JMenuItem}s in
061 * a <code>ButtonGroup</code> because they don't implement the
062 * <code>selected</code> semantics.
063 *
064 * @author original author unknown
065 */
066 public class ButtonGroup implements Serializable
067 {
068 private static final long serialVersionUID = 4259076101881721375L;
069
070 /** Stores references to the buttons added to this button group. */
071 protected Vector<AbstractButton> buttons = new Vector<AbstractButton>();
072
073 /** The currently selected button model. */
074 ButtonModel sel;
075
076 /**
077 * Creates a new button group.
078 */
079 public ButtonGroup()
080 {
081 // Nothing to do here.
082 }
083
084 /**
085 * Adds a button to this group. If the button is in the selected state, then:
086 * <ul>
087 * <li>if the group has no current selection, the new button becomes the
088 * selected button for the group;</li>
089 * <li>if the group already has a selected button, the new button is set to
090 * "not selected".</li>
091 * </ul>
092 *
093 * @param b the button to add (<code>null</code> is ignored).
094 */
095 public void add(AbstractButton b)
096 {
097 if (b == null)
098 return;
099 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 }