透明度渐变效果midp2.0

import java.io.IOException;
import javax.microedition.lcdui.Canvas;
import javax.microedition.lcdui.Display;
import javax.microedition.lcdui.Graphics;
import javax.microedition.lcdui.Image;
import javax.microedition.midlet.MIDlet;
import javax.microedition.midlet.MIDletStateChangeException;

/**
 *
 * @author Jagie
 *
 */
public class ShadowMIDlet
   extends MIDlet {
   Canvas c = new ShadowCanvas();
   public ShadowMIDlet() {
   }

   protected void startApp() throws MIDletStateChangeException {
      Display.getDisplay(this).setCurrent(c);
   }

   protected void pauseApp() {
      // TODO Auto-generated method stub
   }

   protected void destroyApp(boolean arg0) throws MIDletStateChangeException {
      // TODO Auto-generated method stub
   }
}

/**
 *
 * @author Jagie
 *
 */
class ShadowCanvas
   extends Canvas implements Runnable {
   int w, h;
   // 原始图片
   Image srcImage;
   // 原始图片的像素数组
   int[] srcRgbImage;
   // 渐变图片的像素数组
   int[] shadowRgbImage;
   int imgWidth, imgHeight;
   int count;
   public ShadowCanvas() {
      w = this.getWidth();
      h = this.getHeight();
      try {
         srcImage = Image.createImage("/av.png");
      }
      catch (IOException e) {
         // TODO Auto-generated catch block
         e.printStackTrace();
      }
      imgWidth = srcImage.getWidth();
      imgHeight = srcImage.getHeight();
      // 制造原始图片的像素数组，用一个int来代表每一个像素,按位表示方式是:0xAARRGGBB
      srcRgbImage = new int[imgWidth * imgHeight];
      // 获取原始图片的所有像素，参见MIDP APPI文档
      srcImage.getRGB(srcRgbImage, 0, imgWidth, 0, 0, imgWidth, imgHeight);
      shadowRgbImage = new int[srcRgbImage.length];
      System.arraycopy(srcRgbImage, 0, shadowRgbImage, 0,
                       shadowRgbImage.length);
      // 渐变图片的所有像素已开始都是全透明的
      for (int i = 0; i < shadowRgbImage.length; i++) {
         shadowRgbImage[i] &= 0x00ffffff;
      }
      new Thread(this).start();
   }

   public void paint(Graphics g) {
      g.setColor(0, 0, 0);
      g.fillRect(0, 0, w, h);
      // 绘制渐变图片
      g.drawRGB(shadowRgbImage, 0, imgWidth, (w - imgWidth) / 2,
                (h - imgHeight) / 2, imgWidth, imgHeight, true);
      g.setColor(0, 255, 0);
      g.drawString("count=" + count, w / 2, 30, Graphics.HCENTER
                   | Graphics.TOP);
   }

   public void run() {
      while (true) {
         boolean changed = false;
         // 改变渐变图片的每一个像素
         for (int i = 0; i < shadowRgbImage.length; i++) {
            // 获取渐变图片的某一像素的alpha值
            int alpha = (shadowRgbImage & 0xff000000) >>> 24;
            // 原始图片的对应像素的alpha值
            int oldAlpha = (srcRgbImage & 0xff000000) >>> 24;
            if (alpha < oldAlpha) {
               // alpha值++
               shadowRgbImage = ( (alpha + 1) << 24)
                  | (shadowRgbImage & 0x00ffffff);
               changed = true;
            }
         }
         try {
            Thread.sleep(10);
         }
         catch (InterruptedException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
         }
         count++;
         repaint();
         // 当所有像素的alpha值都达到原始值后,线程运行结束
         if (!changed) {
            System.out.println("over");
            break;
         }
      }
   }
}