JRadioButton.java

/* JRadioButton.java -- 
   Copyright (C) 2002, 2004, 2005  Free Software Foundation, Inc.

This file is part of GNU Classpath.

GNU Classpath is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
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any later version.

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General Public License for more details.

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02110-1301 USA.

Linking this library statically or dynamically with other modules is
making a combined work based on this library.  Thus, the terms and
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As a special exception, the copyright holders of this library give you
permission to link this library with independent modules to produce an
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package javax.swing;

import javax.accessibility.AccessibleContext;
import javax.accessibility.AccessibleRole;
import javax.swing.plaf.ButtonUI;

/**
 * The <code>JRadioButton</code> component provides a visually selectable
 * button with mutually exclusive behaviour within a <code>ButtonGroup</code>.
 * A series of radio buttons can be used to provide options to the user,
 * where the user can only select one of the available options.  The state
 * of the button is provided by the superclass, <code>JToggleButton</code>.
 * <code>JRadioButton</code> adds the additional behaviour, that if two
 * or more radio buttons are grouped together, the selection of one implies
 * the deselection of the other buttons within the group.
 * <p>
 *
 * Buttons are grouped by adding each instance to a <code>ButtonGroup</code>.
 * The existence of such a grouping is not reflected visually, so other means
 * should be used to denote this.  For instance, the grouped buttons can be placed
 * within the same panel, possibly with an appropriate border to denote
 * the connection between the components.
 *
 * @author Michael Koch  (konqueror@gmx.de)
 * @author Graydon Hoare  (graydon@redhat.com)
 * @author Andrew John Hughes  (gnu_andrew@member.fsf.org)
 * @see JToggleButton
 * @see ButtonGroup
 * @since 1.2
 */
public class JRadioButton extends JToggleButton
{
  /**
   * Compatible with Sun's JDK.
   */
  private static final long serialVersionUID = 7751949583255506856L;

  /**
   * This class provides accessibility support for the toggle button.
   */
  protected class AccessibleJRadioButton
    extends AccessibleJToggleButton
  {
    private static final long serialVersionUID = 4850967637026120674L;

    /**
     * Constructor for the accessible toggle button.
     */
    protected AccessibleJRadioButton()
    {
        /* Call the superclass to register for events */
        super();
    }

    /**
     * Returns the accessible role for the toggle button.
     *
     * @return An instance of <code>AccessibleRole</code>, describing
     *         the role of the toggle button.
     */
    public AccessibleRole getAccessibleRole()
    {
      return AccessibleRole.RADIO_BUTTON;
    }

  }

  /**
   * Constructs an unselected radio button with no text or icon.
   */ 
  public JRadioButton()
  {
    this(null, null, false);
  }
    
  /**
   * Constructs a radio button using the labelling, state
   * and icon specified by the supplied action.
   *
   * @param a the action to use to define the properties of the button.
   */
  public JRadioButton(Action a)
  {
    this();
    setAction(a);
  }

  /**
   * Constructs an unselected radio button with the supplied icon
   * and no text.
   *
   * @param icon the icon to use.
   */
  public JRadioButton(Icon icon)
  { 
    this(null, icon, false);
  }    
  
  /**
   * Constructs a radio button with the supplied icon and state.
   *
   * @param icon the icon to use.
   * @param selected if true, the radio button is initially in the
   *        selected state.  Otherwise, the button is unselected.
   */
  public JRadioButton(Icon icon, boolean selected)
  { 
    this(null, icon, selected);
  }    
  
  /**
   * Constructs an unselected radio button using the supplied text
   * and no icon.
   *
   * @param text the text to use.
   */
  public JRadioButton(String text)
  {
    this(text, null, false);
  }

  /**
   * Constructs a radio button with the supplied text and state.
   *
   * @param text the text to use.
   * @param selected if true, the radio button is initially in the
   *        selected state.  Otherwise, the button is unselected.
   */
  public JRadioButton(String text, boolean selected)
  {
    this(text, null, selected);
  }
      
  /**
   * Constructs an unselected radio button with the supplied text
   * and icon.
   *
   * @param text the text to use.
   * @param icon the icon to use.
   */
  public JRadioButton(String text, Icon icon)
  {
    this(text, icon, false);
  }
  
  /**
   * Constructs a radio button with the supplied text, icon and state.
   *
   * @param text the text to use.
   * @param icon the icon to use.
   * @param selected if true, the radio button is initially in the
   *        selected state.  Otherwise, the button is unselected.
   */
  public JRadioButton(String text, Icon icon, boolean selected)
  {
    super(text, icon, selected);
    setBorderPainted(false);
    setHorizontalAlignment(LEADING);
  }
      
  /**
   * Returns the accessible context for this <code>JRadioButton</code>,
   * in the form of an instance of <code>AccessibleJRadioButton</code>.
   * The context is created, if necessary.
   *
   * @return the associated context
   */
  public AccessibleContext getAccessibleContext()
  {
    /* Create the context if this is the first request */
    if (accessibleContext == null)
      {
        /* Create the context */
	accessibleContext = new AccessibleJRadioButton();
      }
    return accessibleContext;
  }
  
  /**
   * Returns a string specifying the name of the Look and Feel UI class
   * that renders this component.
   *
   * @return the Look and Feel UI class for <code>JRadioButton</code>s
   *         as a <code>String</code>.
   */  
  public String getUIClassID()
  {
    return "RadioButtonUI";
  }
  
  /**
   * Returns a string representation of this component for debugging use.
   * Users should not depend on anything as regards the content or formatting
   * of this string, except for the fact that the returned string may never be
   * null (only empty).
   *
   * @return the component in <code>String</code> form for debugging.
   */  
  protected  String paramString()
  {
    return super.paramString();
  }
  
  /**
   * This method resets the radio button's UI delegate to the default UI for
   * the current look and feel.
   */
  public void updateUI()
  {
    /* 
       I can't see any difference between this and the superclass one,
       but Sun reimplements it... there is no RadioButtonUI class for it
       to be cast to.
    */
    setUI((ButtonUI) UIManager.getUI(this));
  }

}