J. Duke | 319a3b9 | 2007-12-01 00:00:00 +0000 | [diff] [blame^] | 1 | /* |
| 2 | * Copyright 1997-2006 Sun Microsystems, Inc. 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. Sun designates this |
| 8 | * particular file as subject to the "Classpath" exception as provided |
| 9 | * by Sun 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 Sun Microsystems, Inc., 4150 Network Circle, Santa Clara, |
| 22 | * CA 95054 USA or visit www.sun.com if you need additional information or |
| 23 | * have any questions. |
| 24 | */ |
| 25 | package javax.swing; |
| 26 | |
| 27 | import java.awt.*; |
| 28 | |
| 29 | import javax.swing.plaf.*; |
| 30 | import javax.accessibility.*; |
| 31 | |
| 32 | import java.io.Serializable; |
| 33 | import java.io.ObjectOutputStream; |
| 34 | import java.io.ObjectInputStream; |
| 35 | import java.io.IOException; |
| 36 | |
| 37 | |
| 38 | /** |
| 39 | * <code>JPanel</code> is a generic lightweight container. |
| 40 | * For examples and task-oriented documentation for JPanel, see |
| 41 | * <a |
| 42 | href="http://java.sun.com/docs/books/tutorial/uiswing/components/panel.html">How to Use Panels</a>, |
| 43 | * a section in <em>The Java Tutorial</em>. |
| 44 | * <p> |
| 45 | * <strong>Warning:</strong> Swing is not thread safe. For more |
| 46 | * information see <a |
| 47 | * href="package-summary.html#threading">Swing's Threading |
| 48 | * Policy</a>. |
| 49 | * <p> |
| 50 | * <strong>Warning:</strong> |
| 51 | * Serialized objects of this class will not be compatible with |
| 52 | * future Swing releases. The current serialization support is |
| 53 | * appropriate for short term storage or RMI between applications running |
| 54 | * the same version of Swing. As of 1.4, support for long term storage |
| 55 | * of all JavaBeans<sup><font size="-2">TM</font></sup> |
| 56 | * has been added to the <code>java.beans</code> package. |
| 57 | * Please see {@link java.beans.XMLEncoder}. |
| 58 | * |
| 59 | * @beaninfo |
| 60 | * description: A generic lightweight container. |
| 61 | * |
| 62 | * @author Arnaud Weber |
| 63 | * @author Steve Wilson |
| 64 | */ |
| 65 | public class JPanel extends JComponent implements Accessible |
| 66 | { |
| 67 | /** |
| 68 | * @see #getUIClassID |
| 69 | * @see #readObject |
| 70 | */ |
| 71 | private static final String uiClassID = "PanelUI"; |
| 72 | |
| 73 | /** |
| 74 | * Creates a new JPanel with the specified layout manager and buffering |
| 75 | * strategy. |
| 76 | * |
| 77 | * @param layout the LayoutManager to use |
| 78 | * @param isDoubleBuffered a boolean, true for double-buffering, which |
| 79 | * uses additional memory space to achieve fast, flicker-free |
| 80 | * updates |
| 81 | */ |
| 82 | public JPanel(LayoutManager layout, boolean isDoubleBuffered) { |
| 83 | setLayout(layout); |
| 84 | setDoubleBuffered(isDoubleBuffered); |
| 85 | setUIProperty("opaque", Boolean.TRUE); |
| 86 | updateUI(); |
| 87 | } |
| 88 | |
| 89 | /** |
| 90 | * Create a new buffered JPanel with the specified layout manager |
| 91 | * |
| 92 | * @param layout the LayoutManager to use |
| 93 | */ |
| 94 | public JPanel(LayoutManager layout) { |
| 95 | this(layout, true); |
| 96 | } |
| 97 | |
| 98 | /** |
| 99 | * Creates a new <code>JPanel</code> with <code>FlowLayout</code> |
| 100 | * and the specified buffering strategy. |
| 101 | * If <code>isDoubleBuffered</code> is true, the <code>JPanel</code> |
| 102 | * will use a double buffer. |
| 103 | * |
| 104 | * @param isDoubleBuffered a boolean, true for double-buffering, which |
| 105 | * uses additional memory space to achieve fast, flicker-free |
| 106 | * updates |
| 107 | */ |
| 108 | public JPanel(boolean isDoubleBuffered) { |
| 109 | this(new FlowLayout(), isDoubleBuffered); |
| 110 | } |
| 111 | |
| 112 | /** |
| 113 | * Creates a new <code>JPanel</code> with a double buffer |
| 114 | * and a flow layout. |
| 115 | */ |
| 116 | public JPanel() { |
| 117 | this(true); |
| 118 | } |
| 119 | |
| 120 | /** |
| 121 | * Resets the UI property with a value from the current look and feel. |
| 122 | * |
| 123 | * @see JComponent#updateUI |
| 124 | */ |
| 125 | public void updateUI() { |
| 126 | setUI((PanelUI)UIManager.getUI(this)); |
| 127 | } |
| 128 | |
| 129 | /** |
| 130 | * Returns the look and feel (L&F) object that renders this component. |
| 131 | * |
| 132 | * @return the PanelUI object that renders this component |
| 133 | * @since 1.4 |
| 134 | */ |
| 135 | public PanelUI getUI() { |
| 136 | return (PanelUI)ui; |
| 137 | } |
| 138 | |
| 139 | |
| 140 | /** |
| 141 | * Sets the look and feel (L&F) object that renders this component. |
| 142 | * |
| 143 | * @param ui the PanelUI L&F object |
| 144 | * @see UIDefaults#getUI |
| 145 | * @since 1.4 |
| 146 | * @beaninfo |
| 147 | * bound: true |
| 148 | * hidden: true |
| 149 | * attribute: visualUpdate true |
| 150 | * description: The UI object that implements the Component's LookAndFeel. |
| 151 | */ |
| 152 | public void setUI(PanelUI ui) { |
| 153 | super.setUI(ui); |
| 154 | } |
| 155 | |
| 156 | /** |
| 157 | * Returns a string that specifies the name of the L&F class |
| 158 | * that renders this component. |
| 159 | * |
| 160 | * @return "PanelUI" |
| 161 | * @see JComponent#getUIClassID |
| 162 | * @see UIDefaults#getUI |
| 163 | * @beaninfo |
| 164 | * expert: true |
| 165 | * description: A string that specifies the name of the L&F class. |
| 166 | */ |
| 167 | public String getUIClassID() { |
| 168 | return uiClassID; |
| 169 | } |
| 170 | |
| 171 | |
| 172 | /** |
| 173 | * See readObject() and writeObject() in JComponent for more |
| 174 | * information about serialization in Swing. |
| 175 | */ |
| 176 | private void writeObject(ObjectOutputStream s) throws IOException { |
| 177 | s.defaultWriteObject(); |
| 178 | if (getUIClassID().equals(uiClassID)) { |
| 179 | byte count = JComponent.getWriteObjCounter(this); |
| 180 | JComponent.setWriteObjCounter(this, --count); |
| 181 | if (count == 0 && ui != null) { |
| 182 | ui.installUI(this); |
| 183 | } |
| 184 | } |
| 185 | } |
| 186 | |
| 187 | |
| 188 | /** |
| 189 | * Returns a string representation of this JPanel. This method |
| 190 | * is intended to be used only for debugging purposes, and the |
| 191 | * content and format of the returned string may vary between |
| 192 | * implementations. The returned string may be empty but may not |
| 193 | * be <code>null</code>. |
| 194 | * |
| 195 | * @return a string representation of this JPanel. |
| 196 | */ |
| 197 | protected String paramString() { |
| 198 | return super.paramString(); |
| 199 | } |
| 200 | |
| 201 | ///////////////// |
| 202 | // Accessibility support |
| 203 | //////////////// |
| 204 | |
| 205 | /** |
| 206 | * Gets the AccessibleContext associated with this JPanel. |
| 207 | * For JPanels, the AccessibleContext takes the form of an |
| 208 | * AccessibleJPanel. |
| 209 | * A new AccessibleJPanel instance is created if necessary. |
| 210 | * |
| 211 | * @return an AccessibleJPanel that serves as the |
| 212 | * AccessibleContext of this JPanel |
| 213 | */ |
| 214 | public AccessibleContext getAccessibleContext() { |
| 215 | if (accessibleContext == null) { |
| 216 | accessibleContext = new AccessibleJPanel(); |
| 217 | } |
| 218 | return accessibleContext; |
| 219 | } |
| 220 | |
| 221 | /** |
| 222 | * This class implements accessibility support for the |
| 223 | * <code>JPanel</code> class. It provides an implementation of the |
| 224 | * Java Accessibility API appropriate to panel user-interface |
| 225 | * elements. |
| 226 | * <p> |
| 227 | * <strong>Warning:</strong> |
| 228 | * Serialized objects of this class will not be compatible with |
| 229 | * future Swing releases. The current serialization support is |
| 230 | * appropriate for short term storage or RMI between applications running |
| 231 | * the same version of Swing. As of 1.4, support for long term storage |
| 232 | * of all JavaBeans<sup><font size="-2">TM</font></sup> |
| 233 | * has been added to the <code>java.beans</code> package. |
| 234 | * Please see {@link java.beans.XMLEncoder}. |
| 235 | */ |
| 236 | protected class AccessibleJPanel extends AccessibleJComponent { |
| 237 | |
| 238 | /** |
| 239 | * Get the role of this object. |
| 240 | * |
| 241 | * @return an instance of AccessibleRole describing the role of the |
| 242 | * object |
| 243 | */ |
| 244 | public AccessibleRole getAccessibleRole() { |
| 245 | return AccessibleRole.PANEL; |
| 246 | } |
| 247 | } |
| 248 | } |