// Example of a hierarchical layout

import javax.swing.*;
import javax.swing.event.*;
import java.awt.event.*;
import java.awt.*;

public class Sliders extends JFrame {

    int [] rgb;			// the current colour
    DrawingPanel drawingPanel;	// where we're drawing the oval

    // The panel into which we draw things

    class DrawingPanel extends JPanel {

	DrawingPanel() {
	    setPreferredSize( new Dimension( 400, 200 ) );
	}

	protected void paintComponent( Graphics gContext ) {
	    super.paintComponent( gContext );
	    gContext.setColor( new Color(rgb[0], rgb[1], rgb[2] ) );
	    gContext.fillOval( 10, 10, getWidth()-20, getHeight()-20 );
	}
    }

    // A slider to control one colour component

    class ColourSlider extends JSlider implements ChangeListener {

	int index;

	ColourSlider( int index ) {
	    super( VERTICAL, 0, 255, 200 );
	    this.index = index;
	    addChangeListener( this );
	}

	public void stateChanged( ChangeEvent e ) {
	    rgb[index] = getValue();
	    drawingPanel.repaint();
	}
    }

    // The constructor for this JFrame

    Sliders() {

	super();

	// A panel for three sliders

	rgb = new int[3];
	rgb[0] = 200;
	rgb[1] = 200;
	rgb[2] = 200;

	JPanel sliderPanel = new JPanel();

	ColourSlider rSlider = new ColourSlider( 0 );
	ColourSlider gSlider = new ColourSlider( 1 );
	ColourSlider bSlider = new ColourSlider( 2 );

	rSlider.setValue( rgb[0] );
	rSlider.setValue( rgb[1] );
	rSlider.setValue( rgb[2] );

	sliderPanel.setLayout( new GridLayout(2,3) );

	sliderPanel.add( rSlider ); // top row
	sliderPanel.add( gSlider );
	sliderPanel.add( bSlider );

	sliderPanel.add( new JLabel( "  R  " ) ); // bottom row
	sliderPanel.add( new JLabel( "  G  " ) );
	sliderPanel.add( new JLabel( "  B  " ) );

	// A panel for drawing

	drawingPanel = new DrawingPanel();

	// The JFrame

	Container cp = getContentPane();
	cp.setLayout( new FlowLayout() );
	cp.add( drawingPanel );
	cp.add( sliderPanel );

        pack();
        requestFocus();
        setVisible(true);
    }


    // Test program

    public static void main( String [] args ) {
	Sliders hier = new Sliders();
    }
}