android shape实现阴影或模糊边效果

<?xml version="1.0" encoding="utf-8"? 
<layer-list xmlns:android="http://schemas.android.com/apk/res/android" 
 <!-- 边 -- 
 <item 
  <shape android:shape="rectangle" 
   <padding
    android:bottom="2dp"
    android:left="2dp"
    android:right="2dp"
    android:top="2dp" / 
   <solid android:color="#00CCCCCC" / 
   <corners android:radius="8dp" / 
  </shape 
 </item 
 <item 
  <shape android:shape="rectangle" 
   <padding
    android:bottom="2dp"
    android:left="2dp"
    android:right="2dp"
    android:top="2dp" / 
   <solid android:color="#10CCCCCC" / 
   <corners android:radius="8dp" / 
  </shape 
 </item 
 <item 
  <shape android:shape="rectangle" 
   <padding
    android:bottom="2dp"
    android:left="2dp"
    android:right="2dp"
    android:top="2dp" / 
   <solid android:color="#20CCCCCC" / 
   <corners android:radius="8dp" / 
  </shape 
 </item 
 <item 
  <shape android:shape="rectangle" 
   <padding
    android:bottom="2dp"
    android:left="2dp"
    android:right="2dp"
    android:top="2dp" / 
   <solid android:color="#30CCCCCC" / 
   <corners android:radius="8dp" / 
  </shape 
 </item 
 <item 
  <shape android:shape="rectangle" 
   <padding
    android:bottom="2dp"
    android:left="2dp"
    android:right="2dp"
    android:top="2dp" / 
   <solid android:color="#50CCCCCC" / 
   <corners android:radius="8dp" / 
  </shape 
 </item 

 <!-- 中心背景 -- 
 <item 
  <shape android:shape="rectangle"
   android:useLevel="false" 
   <!-- 实心 -- 
   <solid android:color="#ffffff" / 
   <corners android:radius="10dp" / 
   <padding android:left="10dp"
    android:right="10dp"
    android:top="10dp"
    android:bottom="10dp"/ 
  </shape 
 </item 
</layer-list 

android:background="@drawable/layer_white_bg"