android - Remove action bar shadow -

i want remove shadow appears below appcompat action bar background of action bar transparent.

this theme , action bar style:

<resources>  <!-- base application theme. --> <style name="apptheme" parent="theme.appcompat.light">     <!-- customize theme here. -->     <item name="colorprimary">@color/colorprimary</item>     <item name="colorprimarydark">@color/colorprimarydark</item>     <item name="coloraccent">@color/coloraccent</item>      <item name="android:actionbarstyle">@style/transparentactionbar</item>     <item name="android:windowactionbaroverlay">true</item>      <!-- support library compatibility -->     <item name="actionbarstyle">@style/transparentactionbar</item>     <item name="windowactionbaroverlay">true</item>  </style>  <!-- transparent action bar style --> <style name="transparentactionbar"     parent="widget.appcompat.light.actionbar.solid.inverse">     <item name="android:background">@android:color/transparent</item>      <!-- support library compatibility -->     <item name="background">@android:color/transparent</item>     <item name="elevation">0dp</item> </style> 

my minimum api level 16

i've tried several solutions including:

• setting elevation 0dp works lollipop devices.
• i "resource not found" error if try use windowcontentoverlay
• setting background of root view color white or transparent doesn't work

i've been trying work on 4.4.4 no avail. not possible below api level 21?

edit:

it turns out windowcontentoverlay works android prefix:

<item name="android:windowcontentoverlay">@null<item/> 

trying define without prefix results in resource not found error (this error points 1 prefix whatever reason). don't understand why occurs. can assume appcompat doesn't support windowcontentoverlay attribute.

set windowcontentoverlay drawable drawn under action bar. if don't want shadow set null, so:

<item name="android:windowcontentoverlay">@null</item> 

and

<item name="windowcontentoverlay">@null</item> 

this works api level 16 , up.