android - Could not show text shadow of TextView -

i want make text shadow effect text. use shadow attributes of textview. don't know why not show shadow, have checked on both android studio layout preview , on real device galaxy s3 nothing happen.

help me.

<?xml version="1.0" encoding="utf-8"?> <relativelayout     android:layout_width="wrap_content"     android:layout_height="wrap_content"     xmlns:android="http://schemas.android.com/apk/res/android"     android:background="@color/white">     <textview android:textcolor="@color/black"         android:layout_width="wrap_content"         android:text="text shadow"         android:layout_height="wrap_content"         android:padding="2dp"         android:shadowcolor="#7f000000"         android:shadowdx="3"         android:shadowdy="3"         android:shadowradius="1" /> </relativelayout> 

<linearlayout xmlns:android="http://schemas.android.com/apk/res/android"   android:layout_width="fill_parent" android:layout_height="fill_parent" android:orientation="vertical" android:padding="20dp" >  <textview     android:id="@+id/textview"     android:layout_width="wrap_content"     android:layout_height="wrap_content"     android:layout_gravity="center_horizontal"     android:shadowcolor="#000"     android:shadowdx="0"     android:shadowdy="0"     android:shadowradius="50"     android:text="text shadow example1"     android:textcolor="#fbfbfb"     android:textsize="28dp"     android:textstyle="bold" />  <textview     android:id="@+id/textview2"     android:layout_width="wrap_content"     android:layout_height="wrap_content"     android:layout_gravity="center_horizontal"     android:text="text shadow example2"     android:textcolor="#fbfbfb"     android:textsize="28dp"     android:textstyle="bold" />