圆窗方点 2004.12.2.

//圆窗方点 ycfd.java
import java.applet.Applet;
import java.awt.*;
import java.util.Random; //随机函数

public class xhpp1 extends Applet
implements Runnable //线程可运行状态
{

//变量声明
Thread mainThread; //主线程
Image offScreen;
Image gAlc[];
Random rand;
int stopFlag;
int snows; //雪花数量
int wind;
int threadSleep; //线程休眠
int snowSize; //雪花尺寸
int snowX[]; //雪花 X 坐标
int snowY[]; //雪花 Y 坐标
long stopTime;
Dimension dim;
MediaTracker mt; //图片队列

//构造函数
public xhpp1()
{
stopTime = 0L;
}

//得到一个字符串和一个整数类型的参数
int getParameter(String s, int i)
{
String s1 = getParameter(s);
return s1 == null ? i : Integer.parseInt(s1);
}

//得到一个字符串和三个整数类型的参数
int getParameter(String s, int i, int j, int k)
{
String s1 = getParameter(s);
if(s1 != null)
{
if((i = Integer.parseInt(s1)) > j)
return j;
if(i < k)
return k;
else
return i;
} else
{
return i;
}
}

//得到两个字符串的参数
String getParameter(String s, String s1)
{
String s2 = getParameter(s);
return s2 == null ? s1 : s2;
}

//初始化小程序
public void init()
{
rand = new Random();
dim = getSize();

//屏幕尺寸
offScreen = createImage(dim.width, dim.height);
//雪花数量：10—100个
snows = getParameter("snows", 100, 500, 0);
//雪花尺寸：3—15
snowSize = getParameter("snowSize", 8, 50, 13);
//雪花速度：10—100
threadSleep = getParameter("threadsleep", 50, 1000, 10);
snowX = new int[snows];
snowY = new int[snows];

//产生雪花随机坐标点（X，Y）
for(int i = 0; i < snows; i++)
{
snowX[i] = rand.nextInt() % (dim.width / 2) + dim.width / 2;
snowY[i] = rand.nextInt() % (dim.height / 2) + dim.height / 2;
}

mt = new MediaTracker(this); //图片队列
gAlc = new Image[1];

//取得图片的路径和名称
gAlc[0] = getImage(getDocumentBase(), getParameter("graphic", "test.gif"));
mt.addImage(gAlc[0], 0);
try
{
mt.waitForID(0);
}
catch(InterruptedException interruptedexception)
{
return;
}
stopFlag = 0;
}

//启动小程序
public void start()
{
if(mainThread == null)
{
mainThread = new Thread(this);
mainThread.start();
}
}

//停止小程序
public void stop()
{
mainThread = null;
}

//运行小程序
public void run()
{
while(mainThread != null)
{
try
{
Thread.sleep(threadSleep);
}
catch(InterruptedException interruptedexception)
{
return;
}
repaint();
}
}

//生成雪花
public void drawBackSnow(Graphics g)
{
//设置雪花颜色：红、绿、黄、蓝、白色
g.setColor(Color.white);
for(int i = 0; i < snows; i++)
{

//画圆形填充雪花 fillOval，矩形填充方块 fillRect
g.fillRect(snowX[i], snowY[i], snowSize, snowSize);
snowX[i] += rand.nextInt() % 2 + wind;
snowY[i] += (rand.nextInt() % 6 + 5) / 5 + 1;

//控制雪花的左右界 
if(snowX[i] >= dim.width)
snowX[i] = 0;
if(snowX[i] < 0)
snowX[i] = dim.width - 1;

//控制雪花的上下界
if(snowY[i] >= dim.height || snowY[i] < 0)
{
snowX[i] = Math.abs(rand.nextInt() % dim.width);
snowY[i] = 0;
}
}

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

//画屏函数
public void paint(Graphics g)
{
//设置屏幕背景黑色
offScreen.getGraphics().setColor(Color.black);
//填充矩形屏幕 fillRect，填充圆形屏幕 fillOval
offScreen.getGraphics().fillOval(0,0,dim.width,dim.height);
//绘制雪花
offScreen.getGraphics().drawImage(gAlc[0],0,0,this);
drawBackSnow(offScreen.getGraphics());
g.drawImage(offScreen, 0, 0, null);
}

//更新屏幕函数
public void update(Graphics g)
{
paint(g);
}
}