Source for java.awt.Panel

   1: /* Panel.java -- Simple container object
   2:    Copyright (C) 1999, 2002, 2004, 2005  Free Software Foundation, Inc.
   3: 
   4: This file is part of GNU Classpath.
   5: 
   6: GNU Classpath is free software; you can redistribute it and/or modify
   7: it under the terms of the GNU General Public License as published by
   8: the Free Software Foundation; either version 2, or (at your option)
   9: any later version.
  10: 
  11: GNU Classpath is distributed in the hope that it will be useful, but
  12: WITHOUT ANY WARRANTY; without even the implied warranty of
  13: MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  14: General Public License for more details.
  15: 
  16: You should have received a copy of the GNU General Public License
  17: along with GNU Classpath; see the file COPYING.  If not, write to the
  18: Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
  19: 02110-1301 USA.
  20: 
  21: Linking this library statically or dynamically with other modules is
  22: making a combined work based on this library.  Thus, the terms and
  23: conditions of the GNU General Public License cover the whole
  24: combination.
  25: 
  26: As a special exception, the copyright holders of this library give you
  27: permission to link this library with independent modules to produce an
  28: executable, regardless of the license terms of these independent
  29: modules, and to copy and distribute the resulting executable under
  30: terms of your choice, provided that you also meet, for each linked
  31: independent module, the terms and conditions of the license of that
  32: module.  An independent module is a module which is not derived from
  33: or based on this library.  If you modify this library, you may extend
  34: this exception to your version of the library, but you are not
  35: obligated to do so.  If you do not wish to do so, delete this
  36: exception statement from your version. */
  37: 
  38: 
  39: package java.awt;
  40: 
  41: import javax.accessibility.Accessible;
  42: import javax.accessibility.AccessibleContext;
  43: import javax.accessibility.AccessibleRole;
  44: 
  45: /**
  46:  * A panel is a simple container class. It's default layout is the
  47:  * <code>FlowLayout</code> manager.
  48:  *
  49:  * @author Aaron M. Renn (arenn@urbanophile.com)
  50:  * @author Eric Blake (ebb9@email.byu.edu)
  51:  * @see FlowLayout
  52:  * @since 1.0
  53:  * @status updated to 1.4
  54:  */
  55: public class Panel extends Container implements Accessible
  56: {
  57:   /**
  58:    * Compatible with JDK 1.0+.
  59:    */
  60:   private static final long serialVersionUID = -2728009084054400034L;
  61: 
  62:   /** The cached accessible context. */
  63:   private transient AccessibleContext context;
  64: 
  65:   /** Flag set when the first system-requested paint event is
  66:       dispatched. */
  67:   private transient boolean initialSystemUpdateDone;
  68: 
  69:   /** Flag set when the first application-requested paint event is
  70:       consumed. */
  71:   private transient boolean initialUpdateConsumed;
  72: 
  73:   /*
  74:    * The number used to generate the name returned by getName.
  75:    */
  76:   private static transient long next_panel_number;
  77: 
  78:   /**
  79:    * Initializes a new instance of <code>Panel</code> that has a default
  80:    * layout manager of <code>FlowLayout</code>.
  81:    */
  82:   public Panel()
  83:   {
  84:     this(new FlowLayout());
  85:   }
  86: 
  87:   /**
  88:    * Initializes a new instance of <code>Panel</code> with the specified
  89:    * layout manager.
  90:    *
  91:    * @param layoutManager the layout manager for this object
  92:    * @since 1.1
  93:    */
  94:   public Panel(LayoutManager layoutManager)
  95:   {
  96:     setLayout(layoutManager);
  97:   }
  98: 
  99:   /**
 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: }