ImageView阴影和图层效果

rt 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();            }      }    }