Recipe 14.12 Choosing a Color


Problem

You want to allow the user to select a color from all the colors available on your computer.

Solution

Use Swing's JColorChooser.

Discussion

OK, so it may be just glitz or a passing fad, but with today's displays, the 13 original AWT colors are too limiting. Swing's JColorChooser lets you choose from zillions of colors. From a program's view, it can be used in three ways:

  • Construct it and place it in a panel

  • Call its createDialog( ) and get a JDialog back

  • Call its showDialog( ) and get back the chosen color

We use the last method since it's the simplest and the most likely to be used in a real application. The user has several methods of operating the chooser, too:


Swatches mode

The user can pick from one of a few hundred color variants.


HSB mode

This one's my favorite. The user picks one of Hue, Saturation, or Brightness, a standard way of representing color value. The user can adjust each value by slider. There is a huge range of different pixel values to choose from, by clicking (or, more fun, dragging) in the central area. See Figure 14-11.

Figure 14-11. JColorChooser: HSB view in action
figs/jcb2_1411.gif



RGB mode

The user picks Red, Green, and Blue components by sliders.

Example 14-7 contains a short program that makes it happen.

Example 14-7. JColorDemo.java
import com.darwinsys.util.*; import javax.swing.*; import java.awt.*; import java.awt.event.*; /*   * Colors - demo of Swing JColorChooser.  * Swing's JColorChooser can be used in three ways:  * <UL><LI>Construct it and place it in a panel;  * <LI>Call its createDialog( ) and get a JDialog back  * <LI>Call its showDialog( ) and get back the chosen color  * </UL>  * <P>We use the last method, as it's the simplest, and is how  * you'd most likely use it in a real application.  *  * Originally appeared in the Linux Journal, 1999.  */ public class JColorDemo extends JFrame {     /** A canvas to display the color in. */     JLabel demo;     /** The latest chosen Color */     Color lastChosen;     /** Constructor - set up the entire GUI for this program */     public JColorDemo( ) {         super("Swing Color Demo");         Container cp = getContentPane( );         JButton jButton;         cp.add(jButton = new JButton("Change Color..."), BorderLayout.NORTH);         jButton.setToolTipText("Click here to see the Color Chooser");         jButton.addActionListener(new ActionListener( ) {             public void actionPerformed(ActionEvent actionEvent)             {                 Color ch = JColorChooser.showDialog(                     JColorDemo.this,                // parent                     "Swing Demo Color Popup",    // title                     demo.getForeground( ));            // default                 if (ch != null)                     demo.setForeground(ch);             }         });     cp.add(BorderLayout.CENTER, demo =              new MyLabel("Your One True Color", 200, 100));         demo.setToolTipText("This is the last color you chose");      pack( );     addWindowListener(new WindowCloser(this, true));     }     /** good old main */     public static void main(String[] argv)     {         new JColorDemo( ).setVisible(true);     } }

See Also

This program introduces setToolTipText( ), a method to set the text for pop-up "tooltips" that appear when you position the mouse pointer over a component and don't do anything for a given time (initially half a second). Tooltips originated with Macintosh Balloon Help and were refined into ToolTips under Microsoft Windows.[2] Tooltips are easy to use; the simplest form is shown here. For more documentation, see Chapter 3 of Java Swing.

[2] See? I even said something nice about Microsoft. I do believe in credit where credit's due.



Java Cookbook
Java Cookbook, Second Edition
ISBN: 0596007019
EAN: 2147483647
Year: 2003
Pages: 409
Authors: Ian F Darwin

Similar book on Amazon

flylib.com © 2008-2017.
If you may any questions please contact us: flylib@qtcs.net