How to change direction of android elevation shadow?

The view drop shadow can be translated, or scaled in x and y direction and more by changing the outline provider of the view as detailed in this post.

I consider this method is the best solution: Android Bottom Navigation Bar with drop shadow Thanks, Alexander Bilchuk.

Solution:

You can draw your own shadow just above the view using simple View and its background:

<View
    android:layout_width="match_parent"
    android:layout_height="4dp"
    android:layout_above="@id/bottom_bar"
    android:background="@drawable/shadow"/>

drawable/shadow.xml:

<shape xmlns:android="http://schemas.android.com/apk/res/android">
    <gradient
        android:startColor="#1F000000"
        android:endColor="@android:color/transparent"
        android:angle="90" />
</shape>

Also, there are no compatibility issues if use this approach.