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1   /*
2    * Copyright (c) 1997, 2013, 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://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   */
68  @SuppressWarnings("serial")
69  public class ButtonGroup implements Serializable {
70  
71      // the list of buttons participating in this group
72      protected Vector<AbstractButton> buttons = new Vector<AbstractButton>();
73  
74      /**
75       * The current selection.
76       */
77      ButtonModel selection = null;
78  
79      /**
80       * Creates a new <code>ButtonGroup</code>.
81       */
82      public ButtonGroup() {}
83  
84      /**
85       * Adds the button to the group.
86       * @param b the button to be added
87       */
88      public void add(AbstractButton b) {
89          if(b == null) {
90              return;
91          }
92          buttons.addElement(b);
93  
94          if (b.isSelected()) {
95              if (selection == null) {
96                  selection = b.getModel();
97              } else {
98                  b.setSelected(false);
99              }
100         }
101 
102         b.getModel().setGroup(this);
103     }
104 
105     /**
106      * Removes the button from the group.
107      * @param b the button to be removed
108      */
109     public void remove(AbstractButton b) {
110         if(b == null) {
111             return;
112         }
113         buttons.removeElement(b);
114         if(b.getModel() == selection) {
115             selection = null;
116         }
117         b.getModel().setGroup(null);
118     }
119 
120     /**
121      * Clears the selection such that none of the buttons
122      * in the <code>ButtonGroup</code> are selected.
123      *
124      * @since 1.6
125      */
126     public void clearSelection() {
127         if (selection != null) {
128             ButtonModel oldSelection = selection;
129             selection = null;
130             oldSelection.setSelected(false);
131         }
132     }
133 
134     /**
135      * Returns all the buttons that are participating in
136      * this group.
137      * @return an <code>Enumeration</code> of the buttons in this group
138      */
139     public Enumeration<AbstractButton> getElements() {
140         return buttons.elements();
141     }
142 
143     /**
144      * Returns the model of the selected button.
145      * @return the selected button model
146      */
147     public ButtonModel getSelection() {
148         return selection;
149     }
150 
151     /**
152      * Sets the selected value for the <code>ButtonModel</code>.
153      * Only one button in the group may be selected at a time.
154      * @param m the <code>ButtonModel</code>
155      * @param b <code>true</code> if this button is to be
156      *   selected, otherwise <code>false</code>
157      */
158     public void setSelected(ButtonModel m, boolean b) {
159         if (b && m != null && m != selection) {
160             ButtonModel oldSelection = selection;
161             selection = m;
162             if (oldSelection != null) {
163                 oldSelection.setSelected(false);
164             }
165             m.setSelected(true);
166         }
167     }
168 
169     /**
170      * Returns whether a <code>ButtonModel</code> is selected.
171      * @return <code>true</code> if the button is selected,
172      *   otherwise returns <code>false</code>
173      */
174     public boolean isSelected(ButtonModel m) {
175         return (m == selection);
176     }
177 
178     /**
179      * Returns the number of buttons in the group.
180      * @return the button count
181      * @since 1.3
182      */
183     public int getButtonCount() {
184         if (buttons == null) {
185             return 0;
186         } else {
187             return buttons.size();
188         }
189     }
190 
191 }