Source for javax.swing.JPanel

   1: /* JPanel.java --
   2:    Copyright (C) 2002, 2004, 2006, 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 javax.swing;
  40: 
  41: import java.awt.FlowLayout;
  42: import java.awt.LayoutManager;
  43: 
  44: import javax.accessibility.Accessible;
  45: import javax.accessibility.AccessibleContext;
  46: import javax.accessibility.AccessibleRole;
  47: import javax.swing.plaf.PanelUI;
  48: 
  49: /**
  50:  * An instance of JPanel can be added to a panel, frame etc
  51:  *
  52:  * @author Ronald Veldema (rveldema@cs.vu.nl)
  53:  */
  54: public class JPanel extends JComponent implements Accessible
  55: {
  56:   /**
  57:    * Provides accessibility support for <code>JPanel</code>.
  58:    *
  59:    * @author Roman Kennke (roman@kennke.org)
  60:    */
  61:   protected class AccessibleJPanel extends AccessibleJComponent
  62:   {
  63:     /**
  64:      * Creates a new instance of <code>AccessibleJPanel</code>.
  65:      */
  66:     protected AccessibleJPanel()
  67:     {
  68:       // Nothing to do here.
  69:     }
  70: 
  71:     /**
  72:      * Returns the accessible role for <code>JPanel</code>, which is
  73:      * {@link AccessibleRole#PANEL}.
  74:      *
  75:      * @return the accessible role for <code>JPanel</code>
  76:      */
  77:     public AccessibleRole getAccessibleRole()
  78:     {
  79:       return AccessibleRole.PANEL;
  80:     }
  81:   }
  82: 
  83:   /**
  84:    * Creates a new panel with a new instance of {@link FlowLayout} as the
  85:    * layout manager and double-buffering enabled.
  86:    */
  87:   public JPanel()
  88:   {
  89:     this(new FlowLayout(), true);
  90:   }
  91: 
  92:   /**
  93:    * Creates a new panel with double-buffering enabled or disabled as
  94:    * specified.  The default layout manager is an instance of 
  95:    * {@link FlowLayout}.
  96:    * 
  97:    * @param isDoubleBuffered  a flag that controls whether or not 
  98:    *     double-buffering is enabled.
  99:    */
 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: }