res/layout/gallery_main.xml

<?xml version="1.0" encoding="utf-8"?>
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  MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NON-INFRINGEMENT
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<LinearLayout
    xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    android:id="@+id/drawerLayout"
    android:orientation="vertical"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:fitsSystemWindows="true">

    <RelativeLayout
        android:layout_width="match_parent"
        android:layout_height="match_parent">

        <!-- MAIN CONTENT -->
        <RelativeLayout
            android:id="@+id/gallery_root"
            android:layout_width="match_parent"
            android:layout_height="match_parent">

            <android.support.design.widget.BottomNavigationView
                android:id="@+id/bottom_navigation"
                android:elevation="8dp"
                android:layout_width="match_parent"
                android:layout_height="wrap_content"
                android:layout_alignParentBottom="true"
                app:menu="@menu/navigation_items"
                app:itemBackground="@color/primary"
                app:itemIconTint="@drawable/item_bg"
                app:itemTextColor="@drawable/item_bg" />

            <include layout="@layout/gl_root_group"/>
        </RelativeLayout>

        <!-- This layout will overlap all the others -->
        <include
            android:id="@+id/toolbar"
            layout="@layout/toolbar"  />
    </RelativeLayout>
</LinearLayout>