一)制作要点

1.多线程的使用

2.类java.util.Random的使用

(二)嵌入Applet的HTML页面源代码

SnowPic

注意：上面的图片中java的类名为SnowPic 注意大小写，以及图片的名称Bridge.jpg 和大小1024*768

java源代码

import java.applet.Applet;

import java.awt.*;

import java.util.Random;

public class SnowPic extends Applet implements Runnable

{

Thread mainThread;

Image offScreen,gAlc[];

Random rand;

int stopFlag,snows,wind,threadSleep,snowSize;

int[] snowX,snowY;

long stopTime =0;

Dimension dim;

MediaTracker mt;

public SnowPic(){}

int getParameter(String s1,int s2)

{

String s=getParameter(s1);

return(s !=null)?Integer.parseInt(s):s2;

}

int getParameter(String s1,int s2,int max,int min)

{

String s=getParameter(s1);

if(s!=null)

{

if((s2=Integer.parseInt(s))>max) return max;

else if (s2

else return s2;

}else return s2;

}

String getParameter(String s1 , String s2)

{

String s= getParameter(s1);

return (s!=null)?s:s2;

}

public void init()

{

rand =new Random();

dim =getSize();

offScreen=createImage(dim.width,dim.height);

snows =getParameter("snows",100,500,0);

snowSize =getParameter("snowSize",3,10,3);

threadSleep =getParameter("threadSleep",80,1000,10);

snowX= new int [snows];

snowY = new int [snows];

for( int i=0;i

{

snowX=rand.nextInt()%(dim.width/2)+dim.width/2;

snowY=rand.nextInt()%(dim.height/2)+dim.height/2;

}

mt =new MediaTracker(this);

gAlc= new Image[1];

gAlc[0]=getImage(getDocumentBase(),getParameter("graphic","test.gif"));

mt.addImage(gAlc[0],0);

try

{

mt.waitForID(0);

}

catch(InterruptedException ex) {return;}

stopFlag =0;

}

public void start()

{

if (mainThread==null)

{

mainThread=new Thread(this);

mainThread.start();

}

}

public void stop()

{

mainThread =null;

}

public void run()

{

while(mainThread !=null)

{

try

{

Thread.sleep(threadSleep);

}

catch(InterruptedException ex) {return;}

repaint();

}

}

public void drawBackSnow(Graphics g)

{

g.setColor(Color.white);

for(int i=0;i

{

g.fillOval(snowX,snowY,snowSize,snowSize);

snowX+=rand.nextInt()%2+wind;

snowY+=(rand.nextInt()%6+5)/5+1;

if(snowX>=dim.width) snowX=0;

if(snowX<0) snowX=dim.width -1;

if(snowY>=dim.height ||snowY<0)

{

snowX =Math.abs(rand.nextInt()%dim.width);

snowY =0;

}

}

wind =rand.nextInt()%5 -2;

}

public void paint(Graphics g)

{

offScreen.getGraphics().setColor(Color.black);

offScreen.getGraphics().fillRect(0,0,dim.width,dim.height);

offScreen.getGraphics().drawImage(gAlc[0],0,0,this);

drawBackSnow(offScreen.getGraphics());

g.drawImage(offScreen,0,0,null);

}

public void update(Graphics g)

{

paint(g);

}

}

注意保存为SnowPic.java