Android – add shadow under tabbar – material design

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

<TextView xmlns:android="http://schemas.android.com/apk/res/android"
android:id="@+id/tabText"
android:layout_width="wrap_content"
android:layout_height="@dimen/actionbar_height"
android:textColor="@color/tab_color"
android:gravity="center"
android:textAllCaps="true"
android:singleLine="true" />

resolvent:

<?xml version="1.0" encoding="utf-8"?>
<shape xmlns:android="http://schemas.android.com/apk/res/android">
    <gradient
        android:startColor="@android:color/transparent"
        android:endColor="#33000000"
        android:angle="90">
    </gradient>
</shape>

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="fill_parent"
    android:layout_height="fill_parent">
    <!-- Your views here -->
    <View
        android:layout_width="match_parent"
        android:layout_height="8dp"
        android:background="@drawable/shadow" />
</RelativeLayout>