/** SliderPanel.java -- This panel contains 3 sliders so that
 *  the user can select a color based on the desired amounts
 *  of red/green/blue.
 *  Notice that when we have a slider, we need a "Change" listener
 *  and we listen for change events.  With the slider, we can
 *  call getValue() to find out what the slider is pointing to.
 */
import java.awt.*;
import javax.swing.*;
import javax.swing.event.*;

public class SliderPanel extends JPanel
{
  private JPanel colorPanel;
  private JSlider redSlider, greenSlider, blueSlider;
  private JLabel redLabel, greenLabel, blueLabel;

  public SliderPanel(JPanel p)
  {
    colorPanel = p;
    int defaultRed = 128;
    int defaultGreen = 128;
    int defaultBlue = 255;

    // The 4 parameters to the JSlider constructor are:
    // orientation, min value, max value, default starting value.
    redSlider = new JSlider(JSlider.HORIZONTAL, 0, 255, defaultRed);
    greenSlider = new JSlider(JSlider.HORIZONTAL, 0, 255, defaultGreen);
    blueSlider = new JSlider(JSlider.HORIZONTAL, 0, 255, defaultBlue);

    SliderListener listener = new SliderListener();
    redSlider.addChangeListener(listener);
    greenSlider.addChangeListener(listener);
    blueSlider.addChangeListener(listener);

    redLabel = new JLabel("Red:  " + defaultRed);
    greenLabel = new JLabel("Green:  " + defaultGreen);
    blueLabel = new JLabel("Blue:  " + defaultBlue);

    // Put the labels and corresponding sliders in the Panel.
    add(redLabel);
    add(redSlider);
    add(greenLabel);
    add(greenSlider);
    add(blueLabel);
    add(blueSlider);
  }

  private class SliderListener implements ChangeListener
  {
    public void stateChanged(ChangeEvent e)
    {
      int red = redSlider.getValue();
      int green = greenSlider.getValue();
      int blue = blueSlider.getValue();

      redLabel.setText("Red:  " + red);
      greenLabel.setText("Green:  " + green);
      blueLabel.setText("Blue:  " + blue);

      // When we pass integers to the Color constructor, they are
      // interpreted to be in the range 0-255.
      colorPanel.setBackground(new Color(red, green, blue));
    }
  }
}