Java How to Program Fourth Edition - DCC

Chapter 11 Graphics and Java2D 607
Common Programming Error 11.1
Spelling any static Color class constant with an initial capital letter is a syntax error. 11.1
Two Color constructors are shown in Fig. 11.4—one that takes three int arguments,
and one that takes three float arguments, with each argument specifying the amount of
red, green and blue, respectively. The int values must be between 0 and 255 and the float
values must be between 0.0 and 1.0. The new Color object will have the specified
amounts of red, green and blue. Color methods getRed, getGreen and getBlue
return integer values from 0 to 255 representing the amount of red, green and blue, respectively.
Graphics method getColor returns a Color object representing the current
drawing color. Graphics method setColor sets the current drawing color.
The application of Fig. 11.5 demonstrates several methods from Fig. 11.4 by drawing
filled rectangles and strings in several different colors.
1 // Fig. 11.5: ShowColors.java
2 // Demonstrating Colors.
3
4 // Java core packages
5 import java.awt.*;
6 import java.awt.event.*;
7
8 // Java extension packages
9 import javax.swing.*;
10
11 public class ShowColors extends JFrame {
12
13 // constructor sets window's title bar string and dimensions
14 public ShowColors()
15 {
16 super( "Using colors" );
17
18 setSize( 400, 130 );
19 setVisible( true );
20 }
21
22 // draw rectangles and Strings in different colors
23 public void paint( Graphics g )
24 {
25 // call superclass's paint method
26 super.paint( g );
27
28 // set new drawing color using integers
29 g.setColor( new Color( 255, 0, 0 ) );
30 g.fillRect( 25, 25, 100, 20 );
31 g.drawString( "Current RGB: " + g.getColor(), 130, 40 );
32
33 // set new drawing color using floats
34 g.setColor( new Color( 0.0f, 1.0f, 0.0f ) );
35 g.fillRect( 25, 50, 100, 20 );
36 g.drawString( "Current RGB: " + g.getColor(), 130, 65 );
Fig. Fig. 11.5 11.5 Demonstrating setting and getting a Color (part 1 of 2).
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