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Wednesday, February 22, 2012

RGB Color Chooser Applet Java Code

Posted by on Wednesday, February 22, 2012 Read our previous post
A RGB Color Chooser shows three sliders that the user can manipulate to set the red, green, and blue, components of a color. A color box shows the selected color, and there are three labels that show the numerical values of all the components. Values are in the range 0 to 255. The initial color is black.


An Applet is a program written in the Java programming language that can be included in an HTML page, much in the same way an image is included in a page. 

The program implements an interface called ChangeListener. It defines an object which listens for ChangeEvents. The function stateChange() is a method of the ChangeListener which is invoked when the target of the listener is changed.


Program Code :



/***************************************************************
*     Code 2 Learn Sample Code - http://www.code2learn.com     *
*                                                              *
*                                                              *
*    Please direct all inquiries at codeme@code2learn.com      *
***************************************************************/

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

public class RGMColorChooser extends JApplet
                       implements ChangeListener {

   private JSlider redSlider, greenSlider, blueSlider;

   private JLabel redLabel, greenLabel, blueLabel;

   private JPanel colorbox;
              // Color box for displaying the color.

   public void init() {

       /* Create JSliders with possible values from 0 to 255. */

       redSlider = new JSlider(JSlider.HORIZONTAL, 0, 255, 0);
       greenSlider = new JSlider(JSlider.HORIZONTAL, 0, 255, 0);
       blueSlider = new JSlider(JSlider.HORIZONTAL, 0, 255, 0);

       /* Create JLabels showing current RGB values. */

       redLabel = new JLabel(" R = 0");
       greenLabel = new JLabel(" G = 0");
       blueLabel = new JLabel(" B = 0");

       /* Set the colors of the labels */

       redLabel.setBackground(Color.white);
       redLabel.setForeground(Color.red);
       redLabel.setOpaque(true);
       greenLabel.setBackground(Color.white);
       greenLabel.setForeground(new Color(0,150,0));
       greenLabel.setOpaque(true);
       blueLabel.setBackground(Color.white);
       blueLabel.setForeground(Color.blue);
       blueLabel.setOpaque(true);

       /* Set the applet to listen for changes to the JSliders' values */

       redSlider.addChangeListener(this);
       greenSlider.addChangeListener(this);
       blueSlider.addChangeListener(this);

       /* Create a JPanel whose background color will always be set to the
          currently selected color.  Otherwise, the panel is empty. */

       colorbox = new JPanel();
       colorbox.setBackground(Color.black);

       /* Create the applet layout, which consists of a row of
          three equal-sized regions holding the JSliders,
          the Labels, and the color box. */

       setBackground(Color.gray);
       getContentPane().setBackground(Color.gray);

       getContentPane().setLayout(new GridLayout(1,3,3,3));
       JPanel scrolls = new JPanel();
       JPanel labels = new JPanel();
       scrolls.setBackground(Color.gray);
       labels.setBackground(Color.gray);
       getContentPane().add(scrolls);
       getContentPane().add(labels);
       getContentPane().add(colorbox);

       /* Add the JSliders and the JLabels to their respective panels. */

       scrolls.setLayout(new GridLayout(3,1,2,2));
       scrolls.add(redSlider);
       scrolls.add(greenSlider);
       scrolls.add(blueSlider);

       labels.setLayout(new GridLayout(3,1,2,2));
       labels.add(redLabel);
       labels.add(greenLabel);
       labels.add(blueLabel);

   } 


@Override
    public void stateChanged(ChangeEvent evt) {
        // TODO Auto-generated method stub
        /* This is called when the user has changed the value on
         one of the sliders.  All the sliders are checked,
          the labels are set to display the correct values,
          and the color box is set to correspond to the new color.*/
        int r = redSlider.getValue();
        int g = greenSlider.getValue();
        int b = blueSlider.getValue();
        redLabel.setText(" R = " + r);
        greenLabel.setText(" G = " + g);
        blueLabel.setText(" B = " + b);
        colorbox.setBackground(new Color(r,g,b));

    
}

}  

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