001 /* Panel.java -- Simple container object
002 Copyright (C) 1999, 2002, 2004, 2005 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
039 package java.awt;
040
041 import javax.accessibility.Accessible;
042 import javax.accessibility.AccessibleContext;
043 import javax.accessibility.AccessibleRole;
044
045 /**
046 * A panel is a simple container class. It's default layout is the
047 * <code>FlowLayout</code> manager.
048 *
049 * @author Aaron M. Renn (arenn@urbanophile.com)
050 * @author Eric Blake (ebb9@email.byu.edu)
051 * @see FlowLayout
052 * @since 1.0
053 * @status updated to 1.4
054 */
055 public class Panel extends Container implements Accessible
056 {
057 /**
058 * Compatible with JDK 1.0+.
059 */
060 private static final long serialVersionUID = -2728009084054400034L;
061
062 /** The cached accessible context. */
063 private transient AccessibleContext context;
064
065 /** Flag set when the first system-requested paint event is
066 dispatched. */
067 private transient boolean initialSystemUpdateDone;
068
069 /** Flag set when the first application-requested paint event is
070 consumed. */
071 private transient boolean initialUpdateConsumed;
072
073 /*
074 * The number used to generate the name returned by getName.
075 */
076 private static transient long next_panel_number;
077
078 /**
079 * Initializes a new instance of <code>Panel</code> that has a default
080 * layout manager of <code>FlowLayout</code>.
081 */
082 public Panel()
083 {
084 this(new FlowLayout());
085 }
086
087 /**
088 * Initializes a new instance of <code>Panel</code> with the specified
089 * layout manager.
090 *
091 * @param layoutManager the layout manager for this object
092 * @since 1.1
093 */
094 public Panel(LayoutManager layoutManager)
095 {
096 setLayout(layoutManager);
097 }
098
099 /**
100 * Notifies this object to create its native peer.
101 *
102 * @see #isDisplayable()
103 * @see #removeNotify()
104 */
105 public void addNotify()
106 {
107 if (peer == null)
108 peer = getToolkit().createPanel(this);
109 super.addNotify();
110 }
111
112 /**
113 * Gets the AccessibleContext associated with this panel, creating one if
114 * necessary. This always returns an instance of {@link AccessibleAWTPanel}.
115 *
116 * @return the accessibility context of this panel
117 * @since 1.3
118 */
119 public AccessibleContext getAccessibleContext()
120 {
121 if (context == null)
122 context = new AccessibleAWTPanel();
123 return context;
124 }
125
126 /**
127 * This class provides accessibility support for Panels, and is the
128 * runtime type returned by {@link #getAccessibleContext()}.
129 *
130 * @author Eric Blake (ebb9@email.byu.edu)
131 * @since 1.3
132 */
133 protected class AccessibleAWTPanel extends AccessibleAWTContainer
134 {
135 /**
136 * Compatible with JDK 1.4+.
137 */
138 private static final long serialVersionUID = -6409552226660031050L;
139
140 /**
141 * The default constructor.
142 */
143 protected AccessibleAWTPanel()
144 {
145 }
146
147 /**
148 * Get the role of this accessible object, a panel.
149 *
150 * @return the role of the object
151 * @see AccessibleRole#PANEL
152 */
153 public AccessibleRole getAccessibleRole()
154 {
155 return AccessibleRole.PANEL;
156 }
157 }
158
159 /**
160 * Generate a unique name for this panel.
161 *
162 * @return A unique name for this panel.
163 */
164 String generateName ()
165 {
166 return "panel" + getUniqueLong ();
167 }
168
169 private static synchronized long getUniqueLong ()
170 {
171 return next_panel_number++;
172 }
173 }