app/src/main/res/drawable/side_nav_bar.xml
<shape xmlns:android="http://schemas.android.com/apk/res/android"
android:shape="rectangle">
<gradient
android:angle="135"
android:centerColor="#C9CA1212"
android:endColor="?colorPrimaryVariant"
android:startColor="?colorPrimaryVariant"
android:type="linear" />
</shape>