ImageView阴影和图层效果

import android.app.Activity;  
import android.content.Context;  
import android.graphics.Bitmap;  
import android.graphics.BitmapFactory;  
import android.graphics.Canvas;  
import android.graphics.Color;  
import android.graphics.Paint;  
import android.graphics.PorterDuff;  
import android.graphics.PorterDuff.Mode;  
import android.graphics.PorterDuffXfermode;  
import android.graphics.Rect;  
import android.graphics.RectF;  
import android.graphics.drawable.Drawable;  
import android.os.Bundle;  
import android.view.View;  
  
public class MyCanvasActivity extends Activity {  
    /** Called when the activity is first created. */  
    @Override  
    public void onCreate(Bundle savedInstanceState) {  
        super.onCreate(savedInstanceState);  
        setContentView(new ImageEffect(this));  
    }  
      
  class ImageEffect extends View{  
      Paint paint;  
     public ImageEffect(Context context){  
         super(context);  
         paint= new Paint(); //初始化画笔，为后面阴影效果使用。   
         paint.setAntiAlias(true);//去除锯齿。   
         paint.setShadowLayer(5f, 5.0f, 5.0f, Color.BLACK); //设置阴影层，这是关键。   
         paint.setXfermode(new PorterDuffXfermode(Mode.SRC_IN));  
           
     }  
     public void onDraw(Canvas canvas){  
         super.onDraw(canvas);  
         int posX  = 20;  
         int posY = 50;  
         int PicWidth,PicHeight;  
           
        Drawable drawable = getResources().getDrawable(R.drawable.pic);  
        Drawable dbe    = getResources().getDrawable(R.drawable.pic).mutate();//如果不调用mutate方法，则原图也会被改变，因为调用的资源是同一个，所有对象是共享状态的。   
        Drawable drawTest = getResources().getDrawable(R.drawable.pic);  
        Bitmap bmp = BitmapFactory.decodeResource(getResources(), R.drawable.pic);  
        PicWidth = drawable.getIntrinsicWidth();  
        PicHeight = drawable.getIntrinsicHeight();  
          
        drawTest.setBounds(posX, (2 * posY) + PicHeight, posX + PicWidth, (2 * posY) + 2 * PicHeight );  
        drawable.setBounds(posX,posY,posX+PicWidth,posY+PicHeight);  
        dbe.setBounds(0, 0, PicWidth, PicHeight);  
          
        canvas.drawColor(Color.WHITE);//设置画布颜色   
        canvas.save(Canvas.MATRIX_SAVE_FLAG);  
        dbe.setColorFilter(0x7f000000,PorterDuff.Mode.SRC_IN);  
        canvas.translate(posX + (int)(0.9 * PicWidth/2), posY + PicHeight/2);//图像平移为了刚好在原图后形成影子效果。   
        canvas.skew(-0.9F, 0.0F);//图像倾斜效果。   
        canvas.scale(1.0f, 0.5f);//图像（其实是画布）缩放，Y方向缩小为1/2。   
        dbe.draw(canvas);//此处为画原图像影子效果图，比原图先画，则会在下层。   
        drawable.clearColorFilter();  
        canvas.restore();  
          
       canvas.save(Canvas.MATRIX_SAVE_FLAG);  
        drawable.draw(canvas);//此处为画原图像，由于canvas有层次效果，因此会盖在影子之上。   
        canvas.restore();  
          
        //默认无效果原图   
        canvas.save(Canvas.MATRIX_SAVE_FLAG);  
        drawTest.draw(canvas);  
        canvas.restore();  
          
        //图片阴影效果   
        Rect rect = new Rect(2*posX + PicWidth + 3, 2*posY + PicHeight + 3, 2*posX + 2*PicWidth - 2, 2*posY + 2*PicHeight - 2);  
        //由于图片的实际尺寸比显示出来的图像要大一些，因此需要适当更改下大小，以达到较好的效果   
          
        RectF rectF = new RectF(rect);  
        canvas.drawRoundRect(rectF, 10f, 10f, paint);//在原有矩形基础上，画成圆角矩形，同时带有阴影层。   
        canvas.drawBitmap(bmp, 2*posX + PicWidth, 2*posY + PicHeight, null);//画上原图。   
        canvas.restore();  
        }  
  }  
}