handleexception.java

Java2游戏编程源码 第三章 很好的学习Java和简单游戏编程的书籍

// 程序：使用页面转移处理例外
// 范例文件：HandleException.java

import java.net.*;
import java.awt.*;
import java.applet.*;

public class HandleException extends Applet
{
   int          AppletWidth,AppletHeight,Ascent,Descent,StringWidth,X,Y;
   Image        Bg,Ship1,Ship2,Plane1,Plane2;
   MediaTracker MT;

   URL          ErrorHTML;           

   public void init()
   {
     AppletWidth  = getSize().width;  
     AppletHeight = getSize().height;  


      Bg     = getImage(getDocumentBase(),"Images/1.gif");
      Ship1  = getImage(getDocumentBase(),"Images/3.gif");
      Ship2  = getImage(getDocumentBase(),"Images/4.gif");
      Plane1 = getImage(getDocumentBase(),"Images/5.gif");
      Plane2 = getImage(getDocumentBase(),"Images/6.gif");

      MT = new MediaTracker(this);   
  
      MT.addImage(Bg    ,0);
      MT.addImage(Ship1 ,0);
      MT.addImage(Ship2 ,0);
      MT.addImage(Plane1,0);
      MT.addImage(Plane2,0);

      try
      {        
         showStatus("图像载入中..."); 
         MT.waitForAll();            
      }
      catch(InterruptedException E)  
      { 
         try                          
         {
            ErrorHTML = new URL(getCodeBase().toString() 
                + "ErrorHTML.html");
         }
         catch(MalformedURLException ME){ }

         getAppletContext().showDocument(ErrorHTML); 
      }
   }

   public void paint(Graphics g)
   {
      if((MT.statusAll(false) & MediaTracker.ERRORED)  != 0)
      {
         FontMetrics FM = g.getFontMetrics();

         Ascent      = FM.getAscent();
         Descent     = FM.getDescent();
         StringWidth = FM.stringWidth("载入图像发生错误...");

         X = (AppletWidth - StringWidth) / 2;
         Y = (AppletHeight - (Ascent + Descent)) / 2 + Ascent;

         setBackground(Color.black);              
         g.setColor(Color.white);              
         g.drawString("载入图像发生错误...",X,Y); 

         return;                               
      }   
     
      g.drawImage(Bg    ,0,0,320,240,this);
      g.drawImage(Ship1 ,20,140,80,80,this);
      g.drawImage(Ship2 ,180,140,80,80,this);
      g.drawImage(Plane1,30,10,100,100,this);
      g.drawImage(Plane2,250,50,50,50,this);
   }
}