Solved: How to add dividers in Bottom Navigation View

create a drawable item_bg.xml like this,

<layer-list xmlns:android="http://schemas.android.com/apk/res/android">

    <item>
        <shape android:shape="rectangle" >
            <solid android:color="#F4F4F4" />
        </shape>
    </item>

    <item android:top="-2dp" android:right="-2dp" android:left="-2dp">
        <shape>
            <solid android:color="@android:color/transparent" />
            <stroke
                android:width="1dp"
                android:color="#EAEAEA" />
        </shape>

    </item>

</layer-list>

Then add it to NavigationView as app:itemBackground="@drawable/item_bg"

 <android.support.design.widget.BottomNavigationView
    android:id="@+id/navigation"
    android:layout_width="match_parent"
    android:layout_height="?attr/actionBarSize"
    android:focusable="false"
    app:itemBackground="@drawable/item_bg"
    app:itemIconTint="@color/bottom_navigation_selector"
    app:itemTextColor="@color/bottom_navigation_selector"
    app:layout_anchor="@id/container"
    app:layout_anchorGravity="bottom"
    app:menu="@menu/bottom_nav_items" />