/* Author: Jeff Dalton <J.Dalton@ed.ac.uk>
 * Updated: Fri Jul 13 23:22:36 2001 by Jeff Dalton
 * Copyright: (c) 2001, AIAI, University of Edinburgh
 */

package ix.iface.util;

import javax.swing.*;

import java.awt.event.*;
import java.awt.Component;

/**
 * An object that manages a group of radio buttons in a convenient
 * and easy to use fashion. <p>
 *
 * Essentially it is a JPanel with a BoxLayout, and components of all
 * sorts can be added to it; however, if a JRadioButton is added, the
 * button is to a ButtonGroup and given an ActionListener that records
 * its action command when it is selected.  The most recently selected
 * action command can be obtained by calling the <code>getSelection</code>
 * method.
 */
public class RadioButtonBox extends JPanel {

    protected ButtonGroup group = new ButtonGroup();

    protected String selection = null;

    /** The listener this box attaches to radio buttons. */
    protected ActionListener listener = new ActionListener() {
	public void actionPerformed(ActionEvent event) {
	    selection = event.getActionCommand();
	}
    };

    /**
     * Creates a box that places components along the specified axis.
     *
     * @param axis either <code>BoxLayout.X_AXIS</code> or
     *     <code>BoxLayout.Y_AXIS</code> for a horizontal or
     *     vertical box respectively.
     */
    public RadioButtonBox(int axis) {
	setLayout(new BoxLayout(this, axis));
    }

    /**
     * Creates a RadioButtonBox that arranges components from left to right.
     */
    public static RadioButtonBox createHorizontalBox() {
	return new RadioButtonBox(BoxLayout.X_AXIS);
    }

    /**
     * Creates a RadioButtonBox that arranges components from top to bottom.
     */
    public static RadioButtonBox createVerticalBox() {
	return new RadioButtonBox(BoxLayout.Y_AXIS);
    }

    /**
     * Returns the action command specified by the most recently
     * selected JRadioButton in the box.
     */
    public String getSelection() {
	return selection;
    }

    protected void addImpl(Component comp, Object constraints, int index) {
	if (comp instanceof JRadioButton) {
	    JRadioButton button = (JRadioButton)comp;
	    group.add(button);
	    button.addActionListener(listener);
	    if (button.isSelected())
		selection = button.getActionCommand();
	}
	super.addImpl(comp, constraints, index);
    }

}