Drop shadow on android popup menu

Question

I'm trying to get a drop shadow on a popup menu which is defined as given below -

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:id="@+id/llSortChangePopup"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:orientation="vertical"
    android:background="@color/backgroundColor"
    android:paddingBottom="15dp"
    android:paddingRight="30dp"
    android:paddingLeft="20dp"
    android:paddingTop="15dp"
    android:elevation="2dp"
    >

    <LinearLayout
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:orientation="horizontal"
        android:paddingBottom="20dp"
        android:paddingTop="5dp">

        <ImageView
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:src="@drawable/ic_chat_bubble_outline_black_18dp" />

        <TextView
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:text="Text"
            android:layout_marginLeft="20dp"
            android:paddingTop="3dp"
            android:gravity="center_vertical"
            android:textColor="@color/black"
            android:textSize="16dp"/>

    </LinearLayout>

    <LinearLayout
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:orientation="horizontal"
        android:paddingBottom="20dp"
        android:paddingTop="5dp">

        <ImageView
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:src="@drawable/ic_chat_bubble_outline_black_18dp" />

        <TextView
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:text="More text"
            android:layout_marginLeft="20dp"
            android:paddingTop="3dp"
            android:gravity="center_vertical"
            android:textColor="@color/black"
            android:textSize="16dp"/>

    </LinearLayout>



</LinearLayout>

The problem is - android's design preview shows the drop shadow correctly, but when I run it on a virtual device, nothing shows up. I tried giving elevation attribute of the main layout, a vlaue 0, but to no avail. I also tried this question, I couldn't get it to work, the possible reason being my parent layout in a different xml layout file. What is wrong here?