snowpic.java

java Applet. 功能是模拟下雪.

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 < min) return min ;
           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 < 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);
        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 < snows; i++)
        {

            g.fillOval(snowX[i], snowY[i], snowSize, snowSize);
            snowX[i] += rand.nextInt() % 2 + wind;
            snowY[i] += (rand.nextInt() % 6 + 5) / 5 + 1;
            if(snowX[i] >= dim.width) snowX[i] = 0;
            if(snowX[i] < 0) snowX[i] = dim.width - 1;
            if(snowY[i] >= dim.height || snowY[i] < 0)
            {

                snowX[i] = Math.abs(rand.nextInt() % dim.width);
                snowY[i] = 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);

    }

}