Writing Classes - Java Software Solutions: Foundations of Program Design - page 185

LISTING 4.6 continued

page.drawArc (BASEX+35, BASEY+40, 15, 10, 180, 180); // nose
page.drawArc (BASEX+20, BASEY+50, 40, 15, 180, 180); // mouth

page.setColor (Color.white);
page.drawString ("Always remember that you are unique!",
BASEX-105, BASEY-15);
page.drawString ("Just like everyone else.", BASEX-45, BASEY+105);
}
}

The paintComponent method accepts a Graphics object as a parameter, which,
as we discussed in Chapter 2, represents the graphics context for a component.
Graphics are drawn on the panel by making method calls to the panel's graphics
context (the page parameter).
Every JPanel object has a paintComponent method that automatically
gets called to draw the panel. In this case we are adding to the definition of
paintComponent —telling it that in addition to drawing the background of the
panel, it should also draw the face and words as defined by the various calls made
in the paintComponent method. The first line of the paintComponent method is
a call to super .paintComponent , which represents the regular JPanel version of
the paintComponent method, which handles the painting of the background. We
will almost always use this as the first line of code in a paintComponent method.
Let's look at another example. The Splat class shown in Listing 4.7 contains
a main method that creates and displays the frame for the program. Visually, this

LISTING 4.7

//********************************************************************
// Splat.java Author: Lewis/Loftus
//
// Demonstrates the use of graphical objects.
//********************************************************************

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

public class Splat
{