Android Dialog背景全透明无边框 Theme Style
http://www.cnblogs.com/androidwsjisji/archive/2012/03/14/2395779.html

<style name="Translucent_NoTitle" parent="android:style/Theme.Dialog"><item name="android:windowNoTitle">true</item><item name="android:background">#00000000</item><item name="android:windowBackground">@android:color/transparent</item><item name="android:colorBackgroundCacheHint">@null</item><item name="android:windowIsTranslucent">true</item></style>