import Javax.microedition.midlet.*;
import javax.microedition.lcdui.*;
import java.util.*;
public class TimerDemo extends MIDlet {
Display display;
StarField field = new StarField();
FieldMover mover = new FieldMover();
Timer timer = new Timer();
public TimerDemo() {
display = Display.getDisplay( this );
}
protected void destroyApp( boolean unconditional ) { }
protected void startApp() {
display.setCurrent( field );
timer.schedule( mover, 100, 100 );
}
protected void pauseApp() { }
public void exit(){
timer.cancel(); // stop scrolling
destroyApp( true );
notifyDestroyed();
}
class FieldMover extends TimerTask {
public void run(){
field.scroll();
}
}
class StarField extends Canvas {
int height;
int width;
int[] stars;
Random generator = new Random();
boolean painting = false;
public StarField(){
height = getHeight();
width = getWidth();
stars = new int[ height ];
for( int i = 0; i < height; ++i ){
stars[i] = -1;
}
}
public void scroll() {
if( painting ) return;
for( int i = height-1; i > 0; --i ){
stars[i] = stars[i-1];
}
stars[0] = ( generator.nextInt() % ( 3 * width ) ) / 2;
if( stars[0] >= width ){
stars[0] = -1;
}
repaint();
}
protected void paint( Graphics g ){
painting = true;
g.setColor( 0, 0, 0 );
g.fillRect( 0, 0, width, height );
g.setColor( 255, 255, 255 );
for( int y = 0; y < height; ++y ){
int x = stars[y];
if( x == -1 ) continue;
g.drawLine( x, y, x, y );
}
painting = false;
}
protected void keyPressed( int keyCode ){
exit();
}
}
}
（出处：http://www.knowsky.com）