scroll_1.java

Java 范例实战 光盘使用说明 ========================== 本光盘的文件结构如下所示： =====================================

import java.applet.Applet;
import java.awt.* ;
import java.awt.event.*;

public class Scroll_1 extends Applet implements Runnable 
{

    String text ;
    int xpos, realLength, realHeight, width, height, velocity ;
    boolean threadSuspended = false ;
    Font font ;
    Color fgcolor, bgcolor ;
    Thread mover ;
    Image offScreen ;
    Graphics osGraphics ;

    public Scroll_1()
    {

        xpos = 400;
        width = 400;
        height = 40;
        velocity = 5;
        threadSuspended = false;

    }

    public void init()
    {

        String str = getParameter("text") ;
        text = (str != null) ? str : "No text" ;
        str = getParameter("fontsize") ;
        int fontSize = str == null ? 24 : Integer.parseInt(str) ;
        str = getParameter("fontstyle") ;
	int fontStyle = Font.PLAIN ;
        if (str != null) 
        {
        
          str.toUpperCase() ;
	  if (str.compareTo("ITALIC") == 0) 
	  	fontStyle = Font.ITALIC ;
	  else if (str.compareTo("BOLD") == 0) 
	  	fontStyle = Font.BOLD ;
        
        }
	
	font = new Font("Serif", fontStyle, fontSize) ;
        str = getParameter("velocity") ;
        velocity = str == null ? 5 : Integer.parseInt(str) ;
        str = getParameter("fgcolor") ;
        int c = str == null ? 0 : Integer.parseInt(str, 16) ;
        fgcolor = new Color(c) ;
        str = getParameter("bgcolor") ;
        c = str == null ? 0xffffff : Integer.parseInt(str, 16) ;
        bgcolor = new Color(c) ;
        width = getSize().width ;
        height = getSize().height ;
        offScreen = createImage(width, height) ;
    
    }


    private void paintText(Graphics g)
    {
    
        g.setColor(bgcolor) ;
        g.fillRect(0, 0, width, height) ;
        g.clipRect(0, 0, width, height) ;
        g.setFont(font) ;
        g.setColor(fgcolor) ;
        FontMetrics fontmetrics = g.getFontMetrics() ;
        realLength = fontmetrics.stringWidth(text) ;
        realHeight = fontmetrics.getHeight() ;
        g.drawString(text, xpos, (height + realHeight) / 2) ;
    
    }

    public void paint(Graphics g)
    {
    
        paintText(offScreen.getGraphics());
        g.drawImage(offScreen, 0, 0, null) ;
    
    }

    public void start()
    {
    
        if(mover == null)
        {
    
            mover = new Thread(this) ;
            mover.start() ;
    
        }
    
    }

    public void stop()
    {
    
        mover = null;
    
    }

    private void setcoord()
    {
    
        xpos = xpos - velocity;
        if(xpos < -realLength) xpos = width;
    
    }

    public void run()
    {
    
        while(mover != null)
        {
    
            try
            {
    
                Thread.currentThread().sleep(10L);
    
            }
            catch(InterruptedException _ex) { }
            setcoord() ;
            repaint() ;
    
        }

    }

    public void update(Graphics g)
    {
    
        paint(g) ;
    
    }

    public boolean handleEvent(Event event)
    {
    
        if(event.id == Event.MOUSE_DOWN)
        {
    
            if(threadSuspended)
                mover.resume() ;
            else
                mover.suspend() ;
            threadSuspended = !threadSuspended;
    
        }
        return true;
    
    }

}