Android实现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@R_696_6334@;//去除锯齿。  
   paint.setShadowLayer(5f,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@L_865_6@mutate@L_607_7@，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,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,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(); 
  } 
 } 
}