001 /* JPanel.java --
002 Copyright (C) 2002, 2004, 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
039 package javax.swing;
040
041 import java.awt.FlowLayout;
042 import java.awt.LayoutManager;
043
044 import javax.accessibility.Accessible;
045 import javax.accessibility.AccessibleContext;
046 import javax.accessibility.AccessibleRole;
047 import javax.swing.plaf.PanelUI;
048
049 /**
050 * An instance of JPanel can be added to a panel, frame etc
051 *
052 * @author Ronald Veldema (rveldema@cs.vu.nl)
053 */
054 public class JPanel extends JComponent implements Accessible
055 {
056 /**
057 * Provides accessibility support for <code>JPanel</code>.
058 *
059 * @author Roman Kennke (roman@kennke.org)
060 */
061 protected class AccessibleJPanel extends AccessibleJComponent
062 {
063 /**
064 * Creates a new instance of <code>AccessibleJPanel</code>.
065 */
066 protected AccessibleJPanel()
067 {
068 // Nothing to do here.
069 }
070
071 /**
072 * Returns the accessible role for <code>JPanel</code>, which is
073 * {@link AccessibleRole#PANEL}.
074 *
075 * @return the accessible role for <code>JPanel</code>
076 */
077 public AccessibleRole getAccessibleRole()
078 {
079 return AccessibleRole.PANEL;
080 }
081 }
082
083 /**
084 * Creates a new panel with a new instance of {@link FlowLayout} as the
085 * layout manager and double-buffering enabled.
086 */
087 public JPanel()
088 {
089 this(new FlowLayout(), true);
090 }
091
092 /**
093 * Creates a new panel with double-buffering enabled or disabled as
094 * specified. The default layout manager is an instance of
095 * {@link FlowLayout}.
096 *
097 * @param isDoubleBuffered a flag that controls whether or not
098 * double-buffering is enabled.
099 */
100 public JPanel(boolean isDoubleBuffered)
101 {
102 this(new FlowLayout(), isDoubleBuffered);
103 }
104
105 /**
106 * Creates a new panel with the specified layout manager. Double-buffering
107 * is enabled by default.
108 *
109 * @param layout the layout manager (<code>null</code> permitted).
110 */
111 public JPanel(LayoutManager layout)
112 {
113 this(layout, true);
114 }
115
116 /**
117 * Creates a new panel with the specified layout manager and
118 * double-buffering.
119 *
120 * @param layout the layout manager (<code>null</code> permitted).
121 * @param isDoubleBuffered a flag that controls whether or not
122 * double-buffering is enabled.
123 */
124 public JPanel(LayoutManager layout, boolean isDoubleBuffered)
125 {
126 setLayout(layout);
127 setOpaque(true);
128 setDoubleBuffered(isDoubleBuffered);
129 updateUI();
130 }
131
132 /**
133 * Returns the suffix (<code>"PanelUI"</code> in this case) used to
134 * determine the class name for a UI delegate that can provide the look and
135 * feel for a <code>JPanel</code>.
136 *
137 * @return <code>"PanelUI"</code>.
138 */
139 public String getUIClassID()
140 {
141 return "PanelUI";
142 }
143
144 /**
145 * Sets the UI delegate for the <code>JPanel</code> component.
146 *
147 * @param ui the UI delegate.
148 *
149 * @since 1.4
150 * @see #getUI()
151 */
152 public void setUI(PanelUI ui)
153 {
154 super.setUI(ui);
155 }
156
157 /**
158 * Returns the UI delegate for the <code>JPanel</code> component.
159 *
160 * @return The UI delegate.
161 *
162 * @since 1.4
163 * @see #setUI(PanelUI)
164 */
165 public PanelUI getUI()
166 {
167 return (PanelUI) ui;
168 }
169
170 /**
171 * Sets this panel's UI delegate to the default (obtained from the
172 * {@link UIManager}) for the current look and feel.
173 */
174 public void updateUI()
175 {
176 setUI((PanelUI) UIManager.getUI(this));
177 }
178
179 /**
180 * Returns the object that provides accessibility features for this
181 * <code>JPanel</code> component.
182 *
183 * @return The accessible context (an instance of {@link AccessibleJPanel}).
184 */
185 public AccessibleContext getAccessibleContext()
186 {
187 if (accessibleContext == null)
188 accessibleContext = new AccessibleJPanel();
189 return accessibleContext;
190 }
191
192 /**
193 * Returns an implementation-dependent string describing the attributes of
194 * this <code>JPanel</code>.
195 *
196 * @return A string describing the attributes of this <code>JPanel</code>
197 * (never <code>null</code>).
198 */
199 protected String paramString()
200 {
201 return super.paramString();
202 }
203 }