android:shadow... don't work on TextView

android:shadow... don't work on TextView

i will use this code:
style.xml
<style name="InfoTextStyle" parent="AppBaseTheme">
<item name="android:textColor">#fff</item> <- works
<item name="android:textSize">18sp</item> <- works
<item name="android:shadowColor">#ff0000</item> <- don't works*
<item name="android:shadowRadius">5.0</item> <- *
<item name="android:shadowDx">2.0</item> <- *
<item name="android:shadowDy">2.0</item> <- *
</style>
activity_main.xml
<TextView
android:id="@+id/brightness"
style="@style/InfoTextStyle"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_centerHorizontal="true"
android:layout_gravity="center_horizontal"
android:layout_marginTop="15dp"
android:text="@string/brightness"
android:textAppearance="?android:attr/textAppearanceMedium" />
but the shadow don't work. I'm new in android but what am I doing wrong?,
sorry and thanks!