sky.java

java applet 非常全的实例。比较利于初学者进行研究。

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

public class Sky extends Applet implements Runnable
{
   private Thread thread = null;
   private Color colors[];
   private Image buffer;
   private Graphics gContext;

   int maxpos = 0;
   int red = 0;
   int green = 0;
   int blue = 0;
   int linefactor = 4;
   Image pic;
	
   boolean wait = true;
   boolean redbo = true;
   boolean bluebo = false;
   boolean greenbo = false;
   boolean rise = true;

   public void init(){
      
      String parm;
      colors = new Color[getSize().height/linefactor];
		
      MediaTracker tracker = new MediaTracker(this);
      pic = getImage(getDocumentBase(), getParameter("pic"));
      
      tracker.addImage(pic, 0);
      try {
         tracker.waitForID(0); 
      }	catch(Exception e) {};
      for(maxpos = 0; maxpos<(getSize().height/linefactor)-1 ; maxpos++){
         colors[maxpos]=new Color(0,0,0);
      }
      maxpos = getSize().height;
      buffer = createImage(getSize().width,getSize().height);

      gContext = buffer.getGraphics();
      gContext.setFont(new Font("Arial",Font.BOLD,24));
   }

   public void update(Graphics g){
      if (pic == null)
         return;
      wait = true;
      for(maxpos = 1; maxpos < (getSize().height/linefactor)-1 ; maxpos++)	{
         colors[maxpos-1]=colors[maxpos];
 	 gContext.setColor(colors[maxpos]);
	 gContext.fillRect(0,(maxpos-1)*linefactor ,getSize().width,((maxpos-1)*linefactor)+linefactor);
      }
      createcolorFade();
      colors[maxpos-1]=new Color(red,green,blue);
      gContext.drawImage(pic,0,0,this);

      gContext.setColor(new Color(red,green,blue));

      wait = false;
      paint(g);
   }

   public void paint(Graphics g){
      if(!wait){
         if (buffer!= null){
	    g.drawImage(buffer, 0, 0, null);
	 }
      }
   }

   public void start(){
      if (thread == null){
         thread = new Thread(this);
 	 thread.start();
      }
   }
	
   public void stop(){
      if (thread != null)	{
         thread.stop();
	 thread = null;
      }
   }

   public void run(){
      while (true){
         try{
	    repaint();
	    Thread.sleep(100);
	 }catch (InterruptedException e){
	    stop();
	 }
      }
   }

   public void createcolorFade(){
      if( rise){
         if( redbo == true ){
	    red += 15;
 	    if ( red == 255){
	       redbo = false;
	       greenbo = true;
	    }
	}
	if( greenbo == true ){
 	   green += 15;
	   if ( green == 255){
	      greenbo = false;
	      bluebo = true;
	   }
	}
	if( bluebo == true ){
	   blue += 15;
	   if ( blue == 255){
	      bluebo = false;
	      greenbo = true;
	      rise = false;
	   }
	}
      }else{
         if( greenbo == true ){
	    green -= 15;
	    if ( green == 0){
	       greenbo = false;
	       redbo = true;
	    }
	}
	if( redbo == true ){
  	   red -= 15;
	   if ( red == 0){
	      redbo = false;
	      bluebo = true;
	   }
	}
	if( bluebo == true ){
	   blue -= 15;
	   if ( blue == 0){
	      bluebo = false;
	      redbo = true;
	      rise = true;
	   }
	}
      }
   }

}