1/*
2 * Copyright (c) 1997, 2015, 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 */
25package javax.swing;
26
27import java.awt.event.*;
28import java.util.Vector;
29import java.util.Enumeration;
30import 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://docs.oracle.com/javase/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&trade;
63 * has been added to the <code>java.beans</code> package.
64 * Please see {@link java.beans.XMLEncoder}.
65 *
66 * @author Jeff Dinkins
67 * @since 1.2
68 */
69@SuppressWarnings("serial")
70public class ButtonGroup implements Serializable {
71
72    /**
73     * The list of buttons participating in this group.
74     */
75    protected Vector<AbstractButton> buttons = new Vector<AbstractButton>();
76
77    /**
78     * The current selection.
79     */
80    ButtonModel selection = null;
81
82    /**
83     * Creates a new <code>ButtonGroup</code>.
84     */
85    public ButtonGroup() {}
86
87    /**
88     * Adds the button to the group.
89     * @param b the button to be added
90     */
91    public void add(AbstractButton b) {
92        if(b == null) {
93            return;
94        }
95        buttons.addElement(b);
96
97        if (b.isSelected()) {
98            if (selection == null) {
99                selection = b.getModel();
100            } else {
101                b.setSelected(false);
102            }
103        }
104
105        b.getModel().setGroup(this);
106    }
107
108    /**
109     * Removes the button from the group.
110     * @param b the button to be removed
111     */
112    public void remove(AbstractButton b) {
113        if(b == null) {
114            return;
115        }
116        buttons.removeElement(b);
117        if(b.getModel() == selection) {
118            selection = null;
119        }
120        b.getModel().setGroup(null);
121    }
122
123    /**
124     * Clears the selection such that none of the buttons
125     * in the <code>ButtonGroup</code> are selected.
126     *
127     * @since 1.6
128     */
129    public void clearSelection() {
130        if (selection != null) {
131            ButtonModel oldSelection = selection;
132            selection = null;
133            oldSelection.setSelected(false);
134        }
135    }
136
137    /**
138     * Returns all the buttons that are participating in
139     * this group.
140     * @return an <code>Enumeration</code> of the buttons in this group
141     */
142    public Enumeration<AbstractButton> getElements() {
143        return buttons.elements();
144    }
145
146    /**
147     * Returns the model of the selected button.
148     * @return the selected button model
149     */
150    public ButtonModel getSelection() {
151        return selection;
152    }
153
154    /**
155     * Sets the selected value for the <code>ButtonModel</code>.
156     * Only one button in the group may be selected at a time.
157     * @param m the <code>ButtonModel</code>
158     * @param b <code>true</code> if this button is to be
159     *   selected, otherwise <code>false</code>
160     */
161    public void setSelected(ButtonModel m, boolean b) {
162        if (b && m != null && m != selection) {
163            ButtonModel oldSelection = selection;
164            selection = m;
165            if (oldSelection != null) {
166                oldSelection.setSelected(false);
167            }
168            m.setSelected(true);
169        }
170    }
171
172    /**
173     * Returns whether a {@code ButtonModel} is selected.
174     *
175     * @param m an isntance of {@code ButtonModel}
176     * @return {@code true} if the button is selected,
177     *   otherwise returns {@code false}
178     */
179    public boolean isSelected(ButtonModel m) {
180        return (m == selection);
181    }
182
183    /**
184     * Returns the number of buttons in the group.
185     * @return the button count
186     * @since 1.3
187     */
188    public int getButtonCount() {
189        if (buttons == null) {
190            return 0;
191        } else {
192            return buttons.size();
193        }
194    }
195
196}
197