001    /* JButton.java --
002       Copyright (C) 2002, 2004, 2005, 2006, Free Software Foundation, Inc.
003    
004    This file is part of GNU Classpath.
005    
006    GNU Classpath is free software; you can redistribute it and/or modify
007    it under the terms of the GNU General Public License as published by
008    the Free Software Foundation; either version 2, or (at your option)
009    any later version.
010    
011    GNU Classpath is distributed in the hope that it will be useful, but
012    WITHOUT ANY WARRANTY; without even the implied warranty of
013    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
014    General Public License for more details.
015    
016    You should have received a copy of the GNU General Public License
017    along with GNU Classpath; see the file COPYING.  If not, write to the
018    Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
019    02110-1301 USA.
020    
021    Linking this library statically or dynamically with other modules is
022    making a combined work based on this library.  Thus, the terms and
023    conditions of the GNU General Public License cover the whole
024    combination.
025    
026    As a special exception, the copyright holders of this library give you
027    permission to link this library with independent modules to produce an
028    executable, regardless of the license terms of these independent
029    modules, and to copy and distribute the resulting executable under
030    terms of your choice, provided that you also meet, for each linked
031    independent module, the terms and conditions of the license of that
032    module.  An independent module is a module which is not derived from
033    or based on this library.  If you modify this library, you may extend
034    this exception to your version of the library, but you are not
035    obligated to do so.  If you do not wish to do so, delete this
036    exception statement from your version. */
037    
038    package javax.swing;
039    
040    import gnu.java.lang.CPStringBuilder;
041    
042    import javax.accessibility.Accessible;
043    import javax.accessibility.AccessibleContext;
044    import javax.accessibility.AccessibleRole;
045    import 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     */
054    public 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    }