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: }