<?xml version="1.0" encoding="utf-8"?>
<layer-list xmlns:android="http://schemas.android.com/apk/res/android"> 
<item> 
 <shape android:shape="rectangle">
 <solid android:color="@color/dark_green" /> 
 <corners android:radius="6dp" /> <!--弧度 --> 
 </shape> 
</item> 
<item android:top="8dp" android:right="8dp" android:left="8dp" android:bottom="8dp"> <!--边框宽度 --> 
 <shape android:shape="rectangle"> 
 <solid android:color="@color/white"/> 
 <corners android:radius="6dp" /> 
 <padding android:bottom="8dp" android:left="8dp" android:right="8dp" android:top="8dp"/> 
 </shape>
</item>
</layer-list>

<style name="myCorDialog" parent="android:style/Theme.Dialog"> 
 <item name="android:windowBackground">@drawable/dialog_corner_bg</item> <!-- 背景透明 --> 
 <item name="android:windowNoTitle">true</item> <!-- 没有标题 --> 
 <item name="android:backgroundDimEnabled">true</item> <!-- 背景模糊 --> 
</style>

AlertDialog.Builder builder = new AlertDialog.Builder(this, R.style.myCorDialog);