J2ME特效-粒子模拟瀑布

package ball;

import java.util.Random;

import javax.microedition.lcdui.Canvas;
import javax.microedition.lcdui.Graphics;
import javax.microedition.lcdui.Image;

public class WaterFall extends Canvas implements Runnable
{
final int Max = 1000;
wparticle p[];
int AppletWidth,AppletHeight,XCenter,YCenter;
Image OffScreen;
Graphics drawOffScreen;
Thread pThread;
Random r ;
public WaterFall()
{
setFullScreenMode(true);
}
public void init()
{
AppletWidth = getWidth();
AppletHeight = getHeight();
p = new wparticle[Max];
r = new Random();
for(int i=0; i<Max; i++)
p[i] = new wparticle(r);

OffScreen = Image.createImage(AppletWidth,AppletHeight);
drawOffScreen = OffScreen.getGraphics();
drawOffScreen.setColor(0x0);
}
public void start()
{
pThread = new Thread(this);
pThread.start();
}
public void stop()
{
pThread = null;
}
public void update(Graphics g)
{
paint(g);
}
public void paint(Graphics g)
{
//		g.drawImage(OffScreen,0,0,this);
g.drawImage(OffScreen, 0, 0, Graphics.TOP | Graphics.LEFT);
}
public void run()
{
boolean reset = false;
int i, t =0;
while(true)
{
//			drawOffScreen.clearRect(0,0,AppletWidth,AppletHeight);
//			drawOffScreen.setColor(Color.white);
//			drawOffScreen.drawLine(0,15,10,15);
drawOffScreen.setColor(0x0);
drawOffScreen.fillRect(0, 0, AppletWidth, AppletHeight);
drawOffScreen.setColor(0xffffff);
drawOffScreen.drawLine(0,15,10,15);

for(i=0; i<Max; i++)
{
//				drawOffScreen.fillOval((int)p[i].X,(int)p[i].Y,3,3);
drawOffScreen.setColor(0xffffff);
drawOffScreen.fillArc((int)p[i].X,(int)p[i].Y,3,4, 0, 360);
p[i].X = p[i].X + p[i].Vx;
if(p[i].X > 10)
{
p[i].Y += p[i].Vy*p[i].time / 1000;
p[i].Vy = (int) 9.8*p[i].time;
p[i].time++;
}
if(p[i].Y > AppletHeight)
{
p[i].reset(r);
}
}
repaint();
try
{
Thread.sleep(100);
}
catch (InterruptedException e) { }
}
}
}
class wparticle
{
double X,Y;
double Vx,Vy;
int time;
public wparticle(Random r)
{
reset( r);
}
public void reset(Random r)
{
X = (int) (r.nextDouble() * -40);
Y = (int) (r.nextDouble() * 5 + 10);
Vx = r.nextDouble()*3 + 1.0;
Vy = 0;
time = 0;
}
}