Transparent Activity Android

Use this style   , declare in manifest 

<?xml version="1.0" encoding="utf-8"?>
<resources>
  <style name="Theme.Transparent" parent="android:Theme">
    <item name="android:windowIsTranslucent">true</item>
    <item name="android:windowNoTitle">true</item>
    <item name="android:windowContentOverlay">@null</item>
    <item name="android:backgroundDimEnabled">false</item>

    <item name="android:windowIsFloating">true</item> 

    <item name="android:windowBackground">@android:color/transparent</item> 
  </style>
</resources>

or use 

  android:theme="@android:style/Theme.Translucent"

Download sample code here