gatuttextcrawler.java

本程序执行后

//GatutTextCrawler.java
import java.applet.Applet;
import java.awt.*;
import java.net.InetAddress;
import java.net.UnknownHostException;

public class GatutTextCrawler extends Applet implements Runnable {
    //变量定义	
    Dimension d = null;
    Font font = null;
    FontMetrics fm = null;
    Thread crawler = null;
    String msgText = null,
           fontName = null,
           adds = null;
    int speed = 0,
        fontSize = 0,
        leftLimit = 0,
        y = 0,
        x = 0;
    //构造函数
    public GatutTextCrawler()
    {
    }
    //初始化小程序
    public void init()
    {
        String s;
        
        try
        {
            adds = InetAddress.getLocalHost().toString();
        }
        catch(UnknownHostException _ex)
        {
            adds = "unknown";
        }
        
        s = getParameter("fontSize");
        fontSize = s != null ? Integer.valueOf(s).intValue() : 12;
        s = getParameter("fontName");
        fontName = s != null ? s : "TimesRoman";
        font = new Font(fontName, 0, fontSize);
        
        try
        {
            speed = 100/Integer.valueOf(getParameter("speed"))
                               .intValue();
        }
        catch(Exception _ex)
        {
            speed = 100;
        }
        
        msgText = getParameter("preText") + adds +
                  getParameter("postText");
        d = getSize();
        y = d.height - (d.height - font.getSize()) - 2;
    }
    //画屏函数
    public void paint(Graphics g)
    {
    }
    //更新屏幕函数
    public void update(Graphics g)
    {
        
        if(crawler != null)
        {
            g.setColor(Color.black);
            g.fillRect(0, 0, d.width, d.height);
            g.setFont(font);
            fm = g.getFontMetrics();
            leftLimit = -fm.stringWidth(msgText);
            x--;
        
            if(x < leftLimit)
                x = d.width;
        
            g.setColor(Color.white);
            g.drawString(msgText, x, y);
        }
        
    }
    //启动小程序
    public void start()
    {
        crawler = new Thread(this);
        crawler.start();
    }
    //停止小程序
    public void stop()
    {
        crawler.stop();
    }
    //运行小程序
    public void run()
    {
        
        while(crawler != null)
        {
        
            try
            {
                Thread.currentThread();
                Thread.sleep(speed);
            }
            catch(InterruptedException _ex) { }
        
            repaint();
        }
        
    }    
}