1 /*
2 * Copyright (c) 1997, 2008, Oracle and/or its affiliates. All rights reserved.
3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
4 *
5 * This code is free software; you can redistribute it and/or modify it
6 * under the terms of the GNU General Public License version 2 only, as
7 * published by the Free Software Foundation. Oracle designates this
8 * particular file as subject to the "Classpath" exception as provided
9 * by Oracle in the LICENSE file that accompanied this code.
10 *
11 * This code is distributed in the hope that it will be useful, but WITHOUT
12 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
13 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
14 * version 2 for more details (a copy is included in the LICENSE file that
15 * accompanied this code).
16 *
17 * You should have received a copy of the GNU General Public License version
18 * 2 along with this work; if not, write to the Free Software Foundation,
19 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
20 *
21 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
22 * or visit www.oracle.com if you need additional information or have any
23 * questions.
24 */
25 package javax.swing;
26
27 import java.awt.event;
28 import java.util.Vector;
29 import java.util.Enumeration;
30 import java.io.Serializable;
31
32 /**
33 * This class is used to create a multiple-exclusion scope for
34 * a set of buttons. Creating a set of buttons with the
35 * same <code>ButtonGroup</code> object means that
36 * turning "on" one of those buttons
37 * turns off all other buttons in the group.
38 * <p>
39 * A <code>ButtonGroup</code> can be used with
40 * any set of objects that inherit from <code>AbstractButton</code>.
41 * Typically a button group contains instances of
42 * <code>JRadioButton</code>,
43 * <code>JRadioButtonMenuItem</code>,
44 * or <code>JToggleButton</code>.
45 * It wouldn't make sense to put an instance of
46 * <code>JButton</code> or <code>JMenuItem</code>
47 * in a button group
48 * because <code>JButton</code> and <code>JMenuItem</code>
49 * don't implement the selected state.
50 * <p>
51 * Initially, all buttons in the group are unselected.
52 * <p>
53 * For examples and further information on using button groups see
54 * <a href="http://java.sun.com/docs/books/tutorial/uiswing/components/button.html#radiobutton">How to Use Radio Buttons</a>,
55 * a section in <em>The Java Tutorial</em>.
56 * <p>
57 * <strong>Warning:</strong>
58 * Serialized objects of this class will not be compatible with
59 * future Swing releases. The current serialization support is
60 * appropriate for short term storage or RMI between applications running
61 * the same version of Swing. As of 1.4, support for long term storage
62 * of all JavaBeans<sup><font size="-2">TM</font></sup>
63 * has been added to the <code>java.beans</code> package.
64 * Please see {@link java.beans.XMLEncoder}.
65 *
66 * @author Jeff Dinkins
67 */
68 public class ButtonGroup implements Serializable {
69
70 // the list of buttons participating in this group
71 protected Vector<AbstractButton> buttons = new Vector<AbstractButton>();
72
73 /**
74 * The current selection.
75 */
76 ButtonModel selection = null;
77
78 /**
79 * Creates a new <code>ButtonGroup</code>.
80 */
81 public ButtonGroup() {}
82
83 /**
84 * Adds the button to the group.
85 * @param b the button to be added
86 */
87 public void add(AbstractButton b) {
88 if(b == null) {
89 return;
90 }
91 buttons.addElement(b);
92
93 if (b.isSelected()) {
94 if (selection == null) {
95 selection = b.getModel();
96 } else {
97 b.setSelected(false);
98 }
99 }
100
101 b.getModel().setGroup(this);
102 }
103
104 /**
105 * Removes the button from the group.
106 * @param b the button to be removed
107 */
108 public void remove(AbstractButton b) {
109 if(b == null) {
110 return;
111 }
112 buttons.removeElement(b);
113 if(b.getModel() == selection) {
114 selection = null;
115 }
116 b.getModel().setGroup(null);
117 }
118
119 /**
120 * Clears the selection such that none of the buttons
121 * in the <code>ButtonGroup</code> are selected.
122 *
123 * @since 1.6
124 */
125 public void clearSelection() {
126 if (selection != null) {
127 ButtonModel oldSelection = selection;
128 selection = null;
129 oldSelection.setSelected(false);
130 }
131 }
132
133 /**
134 * Returns all the buttons that are participating in
135 * this group.
136 * @return an <code>Enumeration</code> of the buttons in this group
137 */
138 public Enumeration<AbstractButton> getElements() {
139 return buttons.elements();
140 }
141
142 /**
143 * Returns the model of the selected button.
144 * @return the selected button model
145 */
146 public ButtonModel getSelection() {
147 return selection;
148 }
149
150 /**
151 * Sets the selected value for the <code>ButtonModel</code>.
152 * Only one button in the group may be selected at a time.
153 * @param m the <code>ButtonModel</code>
154 * @param b <code>true</code> if this button is to be
155 * selected, otherwise <code>false</code>
156 */
157 public void setSelected(ButtonModel m, boolean b) {
158 if (b && m != null && m != selection) {
159 ButtonModel oldSelection = selection;
160 selection = m;
161 if (oldSelection != null) {
162 oldSelection.setSelected(false);
163 }
164 m.setSelected(true);
165 }
166 }
167
168 /**
169 * Returns whether a <code>ButtonModel</code> is selected.
170 * @return <code>true</code> if the button is selected,
171 * otherwise returns <code>false</code>
172 */
173 public boolean isSelected(ButtonModel m) {
174 return (m == selection);
175 }
176
177 /**
178 * Returns the number of buttons in the group.
179 * @return the button count
180 * @since 1.3
181 */
182 public int getButtonCount() {
183 if (buttons == null) {
184 return 0;
185 } else {
186 return buttons.size();
187 }
188 }
189
190 }