/**
 * The code in this file displays a set of 3 JRadioButtons.  When one is clicked,
 * the background is changed appropriately and a JLabel that shows
 * the currently selected color is updated.
 * 
 * @author John Paxton
 * @version 1.0
 */

import javax.swing.JPanel;
import javax.swing.JRadioButton;
import javax.swing.ButtonGroup;
import javax.swing.JLabel;

import java.awt.Color;
import java.awt.Graphics;

import java.awt.event.ActionListener;
import java.awt.event.ActionEvent;

public class MyPanel extends JPanel
{
    /**
     * Class constructor.
     */
    
    MyPanel()
    {
        currentBackground = Color.red;
        colorGroup = new ButtonGroup();
        add (new MyButton("Blue", this, Color.blue, colorGroup));
        add (new MyButton("Yellow", this, Color.yellow, colorGroup));
        add (new MyButton("Green", this, Color.green, colorGroup));
        add (new JLabel("Color Selected: "));
        selectedLabel = new JLabel("Unselected");
        add (selectedLabel);
    }
    
    // An inner class.
    
    class MyButton extends JRadioButton implements ActionListener
    {
        /**
         * Class constructor for a custom JRadioButton.
         * 
         * @author John Paxton
         * @version 1.01, 01-23-2006
         * 
         * @param   label   the label for the button
         * @param   parent  the JPanel in which this button resides
         * @param   background  the color to set the background of the JPanel
         * @param   group   the logical group to which this JRadioButton belongs
         */
        
        MyButton (String label, MyPanel parent, Color background, ButtonGroup group)
        {
            group.add(this);
            setContentAreaFilled(false);
            setText(label);
            addActionListener(this);
            this.parent = parent;
            color = background;
        }
        
        /**
         * Specifies what to do when a JRadioButton is clicked.
         * 
         * @param   evt     the event that occurred
         */
        
        public void actionPerformed (ActionEvent evt)
        {
            currentBackground = color;
            selectedLabel.setText(evt.getActionCommand());
            parent.repaint();
        }
        
        /**
         * Adds one to the parameter passed into it.
         * 
         * @param   n   a number to add one to
         * @return  the new number
         */
        
        public int addOne (int n)
        {
            return n + 1;
        }
        
        private MyPanel parent;     // the JPanel that contains this JRadioButton
        private Color color;        // the desired background for the containing JPanel
    } 
    
    /**
     * Displays the appropriate information in the JPanel
     * 
     * @param   g   the drawing object
     */
        
    public void paintComponent (Graphics g)
    {
        super.paintComponent(g);
        setBackground(currentBackground);
    }
    
    private Color currentBackground;    // current background of JPanel 
    private ButtonGroup colorGroup;     // to logically organize the color JRadioButtons
    private JLabel selectedLabel;       // shows the currently selected color
}