Java Swing, 2nd Edition

Developing a Custom Chooser Panel

If you look at the JColorChooser component, you’ll realize that it is really just a tabbed pane with a color previewer below it. You can have as many chooser panels in it as you like. Let’s take a brief look at a panel that can be added to a color chooser. We’ll create a simple panel for selecting a shade of gray with one slider rather than pushing each slider for red, green, and blue to the same value. Figure 12-8 shows the resulting panel; its source code is presented here.

// GrayScalePanel.java // A simple implementation of the AbstractColorChooserPanel class. This class // provides a slider and a text field for picking out a shade of gray. // import java.awt.*; import java.awt.event.*; import javax.swing.*; import javax.swing.event.*; import javax.swing.colorchooser.*; public class GrayScalePanel extends AbstractColorChooserPanel implements ChangeListener, ActionListener { JSlider scale; JTextField percentField; // Set up our list of grays. We'll assume we have all 256 possible shades, // and we'll do it when the class is loaded. static Color[] grays = new Color[256]; static { for (int i=0; i<256; i++) { grays[i] = new Color(i, i, i); } } public GrayScalePanel( ) { setLayout(new GridLayout(0, 1)); // Create the slider and attach us as a listener. scale = new JSlider(JSlider.HORIZONTAL, 0, 255, 128); scale.addChangeListener(this); // Set up our display for the chooser. add(new JLabel("Pick your shade of gray:", JLabel.CENTER)); JPanel jp = new ...