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 }