remove elivation on android studio bottom navigation bar
<android.support.design.widget.BottomNavigationView android:id="@+id/bottom_navigation" android:layout_width="match_parent" android:layout_height="wrap_content" android:layout_alignParentBottom="true" android:background="@android:color/white" app:elevation="0dp" app:menu="@menu/bottom_navigation_main" />