A RGBColorChooser shows three sliders that the user can manipulate to set the red, green, and blue, components of a color. A color patch 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.
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import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
import javax.swing.event.*;
public class RGBColorChooser extends JApplet
implements ChangeListener {
private JSlider redSlider, greenSlider, blueSlider;
// For setting the color.
private JLabel redLabel, greenLabel, blueLabel;
// For displaying RGB values.
private JPanel colorPatch;
// Color patch 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 and HSB values. */
redLabel = new JLabel(" R = 0");
greenLabel = new JLabel(" G = 0");
blueLabel = new JLabel(" B = 0");
/* Set the colors of the labels, and make them opaque */
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. */
colorPatch = new JPanel();
colorPatch.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 patch. The background color
of the applet is gray, which will show around the edges
and between components. */
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(colorPatch);
/* 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);
} // end init();
public void stateChanged(ChangeEvent evt) {
// 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 patch 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);
colorPatch.setBackground(new Color(r,g,b));
} // end stateChanged
public Insets getInsets() {
// The system calls this method to find out how much space to
// leave between the edges of the applet and the components that
// it contains. I want a 3-pixel border at each edge.
return new Insets(3,3,3,3);
}
} // end class RGBColorChooser
