child_bg.xml

<?xml version="1.0" encoding="utf-8"?>
<layer-list xmlns:android="http://schemas.android.com/apk/res/android" >

    <item>
        <shape>
            <gradient
                android:angle="0"
                android:centerColor="#CCCCCC"
                android:endColor="#FFFFFF"
                android:height="1px"
                android:startColor="#FFFFFF" />
        </shape>
    </item>

</layer-list>