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 }