Threaded Java - Java - page 860

Solution

Use a background thread to drive the animation.

Discussion

One common use of threads is an animator, a class that displays a moving image. This “an-
imator” program does just that. It draws a graphical image (see Drawing an Image ) at loca-
tions around the screen; the location is updated and redrawn from a Thread for each such im-
age. This version is an applet, so we see it here in the AppletViewer ( Figure 22-1 ).

Figure 22-1. Animator

The code for the animator program consists of two classes, Sprite (see Example 22-5 ) and
Bounce [ 62 ] (see Example 22-6 ) . A Sprite is one image that moves around; Bounce is the
main program.

Example 22-5. threads/Sprite.java (part of animator program)
/** A Sprite is one Image that moves around the screen on its own */
public

public class class Sprite Sprite extends extends Component implements implements Runnable {

protected protected static static int int spriteNumber = 0 ;

protected protected Thread t ;

protected protected int int x , y ;

protected protected Component parent ;

protected

protected Image img ;