001/* JButton.java --
002   Copyright (C) 2002, 2004, 2005, 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
038package javax.swing;
039
040import gnu.java.lang.CPStringBuilder;
041
042import javax.accessibility.Accessible;
043import javax.accessibility.AccessibleContext;
044import javax.accessibility.AccessibleRole;
045import javax.swing.plaf.ButtonUI;
046
047
048/**
049 * A general purpose push button. <code>JButton</code>s can display a label,
050 * an {@link Icon} or both.
051 *
052 * @author Ronald Veldema (rveldema@cs.vu.nl)
053 */
054public class JButton extends AbstractButton
055  implements Accessible
056{
057
058  /**
059   * Accessibility support for JButtons.
060   */
061  protected class AccessibleJButton
062    extends AbstractButton.AccessibleAbstractButton
063  {
064    /**
065     * Returns the accessible role that this component represents.
066     * This is {@link AccessibleRole#PUSH_BUTTON} for <code>JButton</code>s.
067     *
068     * @return the accessible role that this component represents
069     */
070    public AccessibleRole getAccessibleRole()
071    {
072      return AccessibleRole.PUSH_BUTTON;
073    }
074  }
075
076  private static final long serialVersionUID = -1907255238954382202L;
077
078  /**
079   * Indicates if this button is capable to become the default button.
080   */
081  private boolean defaultCapable;
082
083  /**
084   * Creates a new button with an empty string for the button text and no
085   * icon.
086   */
087  public JButton()
088  {
089    this(null, null);
090  }
091
092  /**
093   * Creates a new button from the specified action.
094   *
095   * @param a  the action (<code>null</code> permitted).
096   *
097   * @see AbstractButton#setAction(Action)
098   */
099  public JButton(Action a)
100  {
101    this();
102    setAction(a);
103  }
104
105  /**
106   * Creates a new button with the specified icon (and an empty string for
107   * the button text).
108   *
109   * @param icon  the icon (<code>null</code> permitted).
110   */
111  public JButton(Icon icon)
112  {
113    this(null, icon);
114  }
115
116  /**
117   * Creates a new button with the specified text and no icon.
118   *
119   * @param text  the button text (<code>null</code> permitted, will be
120   *     substituted by an empty string).
121   */
122  public JButton(String text)
123  {
124    this(text, null);
125  }
126
127  /**
128   * Creates a new button with the specified text and icon.
129   *
130   * @param text  the button text (<code>null</code> permitted, will be
131   *     substituted by an empty string).
132   * @param icon  the icon (<code>null</code> permitted).
133   */
134  public JButton(String text, Icon icon)
135  {
136    super();
137    setModel(new DefaultButtonModel());
138    init(text, icon);
139    defaultCapable = true;
140  }
141
142  protected void configurePropertiesFromAction(Action a)
143  {
144    super.configurePropertiesFromAction(a);
145  }
146
147  /**
148   * Returns the object that provides accessibility features for this
149   * <code>JButton</code> component.
150   *
151   * @return The accessible context (an instance of {@link AccessibleJButton}).
152   */
153  public AccessibleContext getAccessibleContext()
154  {
155    if (accessibleContext == null)
156      accessibleContext = new AccessibleJButton();
157    return accessibleContext;
158  }
159
160  /**
161   * Returns the suffix (<code>"ButtonUI"</code> in this case) used to
162   * determine the class name for a UI delegate that can provide the look and
163   * feel for a <code>JButton</code>.
164   *
165   * @return <code>"ButtonUI"</code>.
166   */
167  public String getUIClassID()
168  {
169    // Returns a string that specifies the name of the L&F class that renders
170    // this component.
171    return "ButtonUI";
172  }
173
174  /**
175   * Returns <code>true</code> if this button is the default button in
176   * its <code>JRootPane</code>. The default button gets automatically
177   * activated when the user presses <code>ENTER</code> (or whatever
178   * key this is bound to in the current Look and Feel).
179   *
180   * @return <code>true</code> if this button is the default button in
181   *         its <code>JRootPane</code>
182   *
183   * @see #isDefaultCapable()
184   * @see #setDefaultCapable(boolean)
185   * @see JRootPane#getDefaultButton()
186   * @see JRootPane#setDefaultButton(JButton)
187   */
188  public boolean isDefaultButton()
189  {
190    // The default button is managed by the JRootPane, so the safest way
191    // to determine this property is to ask the root pane of this button,
192    // if it exists.
193    JRootPane rp = SwingUtilities.getRootPane(this);
194    boolean isDefault = false;
195    if (rp != null)
196      isDefault = rp.getDefaultButton() == this;
197    return isDefault;
198  }
199
200  /**
201   * Returns <code>true</code> if this button can act as the default button.
202   * This is <code>true</code> by default.
203   *
204   * @return <code>true</code> if this button can act as the default button
205   *
206   * @see #setDefaultCapable(boolean)
207   * @see #isDefaultButton()
208   * @see JRootPane#getDefaultButton()
209   * @see JRootPane#setDefaultButton(JButton)
210   */
211  public boolean isDefaultCapable()
212  {
213    // Returns whether or not this button is capable of being the default
214    // button on the RootPane.
215    return defaultCapable;
216  }
217
218  /**
219   * Returns an implementation-dependent string describing the attributes of
220   * this <code>JButton</code>.
221   *
222   * @return A string describing the attributes of this <code>JButton</code>
223   *         (never <code>null</code>).
224   */
225  protected String paramString()
226  {
227    String superParam = super.paramString();
228
229    // 41 is the maximum number of chars which may be needed.
230    CPStringBuilder sb = new CPStringBuilder(41);
231    sb.append(",defaultButton=").append(isDefaultButton());
232    sb.append(",defaultCapable=").append(defaultCapable);
233
234    return superParam + sb.toString();
235  }
236
237  /**
238   * Overrides JComponent.removeNotify to check if this button is currently
239   * set as the default button on the RootPane, and if so, sets the RootPane's
240   * default button to null to ensure the RootPane doesn't hold onto an invalid
241   * button reference.
242   */
243  public void removeNotify()
244  {
245    JRootPane root = SwingUtilities.getRootPane(this);
246    if (root != null && root.getDefaultButton() == this)
247      root.setDefaultButton(null);
248    super.removeNotify();
249  }
250
251  /**
252   * Sets the <code>defaultCapable</code> property which indicates if
253   * this button may become the default button in its <code>JRootPane</code>.
254   *
255   * @param defaultCapable <code>true</code> if this button can become the
256   *        default button in its JRootPane, <code>false</code> otherwise
257   *
258   * @see #setDefaultCapable(boolean)
259   * @see #isDefaultButton()
260   * @see JRootPane#getDefaultButton()
261   * @see JRootPane#setDefaultButton(JButton)
262   */
263  public void setDefaultCapable(boolean defaultCapable)
264  {
265    this.defaultCapable = defaultCapable;
266  }
267
268  /**
269   * Sets this button's UI delegate to the default (obtained from the
270   * {@link UIManager}) for the current look and feel.
271   */
272  public void updateUI()
273  {
274    setUI((ButtonUI) UIManager.getUI(this));
275  }
276}