001/* JPanel.java --
002   Copyright (C) 2002, 2004, 2006, Free Software Foundation, Inc.
003
004This file is part of GNU Classpath.
005
006GNU Classpath is free software; you can redistribute it and/or modify
007it under the terms of the GNU General Public License as published by
008the Free Software Foundation; either version 2, or (at your option)
009any later version.
010
011GNU Classpath is distributed in the hope that it will be useful, but
012WITHOUT ANY WARRANTY; without even the implied warranty of
013MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
014General Public License for more details.
015
016You should have received a copy of the GNU General Public License
017along with GNU Classpath; see the file COPYING.  If not, write to the
018Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
01902110-1301 USA.
020
021Linking this library statically or dynamically with other modules is
022making a combined work based on this library.  Thus, the terms and
023conditions of the GNU General Public License cover the whole
024combination.
025
026As a special exception, the copyright holders of this library give you
027permission to link this library with independent modules to produce an
028executable, regardless of the license terms of these independent
029modules, and to copy and distribute the resulting executable under
030terms of your choice, provided that you also meet, for each linked
031independent module, the terms and conditions of the license of that
032module.  An independent module is a module which is not derived from
033or based on this library.  If you modify this library, you may extend
034this exception to your version of the library, but you are not
035obligated to do so.  If you do not wish to do so, delete this
036exception statement from your version. */
037
038
039package javax.swing;
040
041import java.awt.FlowLayout;
042import java.awt.LayoutManager;
043
044import javax.accessibility.Accessible;
045import javax.accessibility.AccessibleContext;
046import javax.accessibility.AccessibleRole;
047import 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 */
054public 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}