CoordinatorLayout + AppBarLayout + NavigationDrawer

Your CoordinatorLayout is wrapping your DrawerLayout and NavigationView, which means the Coordinator is in control of how everything is laid out. You need to nest the Coordinator inside the drawer, like so:

<android.support.v4.widget.DrawerLayout
    xmlns:android="http://schemas.android.com/apk/res/android"
    android:id="@+id/drawer_layout"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:clickable="true"
    android:focusableInTouchMode="true">

    <android.support.design.widget.CoordinatorLayout
        xmlns:app="http://schemas.android.com/apk/res-auto"
        android:id="@+id/overview_coordinator_layout"
        android:layout_width="match_parent"
        android:layout_height="match_parent">

        <android.support.design.widget.AppBarLayout
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:theme="@style/ThemeOverlay.AppCompat.Dark.ActionBar">


            <android.support.v7.widget.Toolbar
                android:id="@+id/toolbar"
                android:layout_width="match_parent"
                android:layout_height="?attr/actionBarSize"
                android:background="?attr/colorPrimaryDark"
                app:layout_scrollFlags="enterAlways|scroll" />

        </android.support.design.widget.AppBarLayout>

        <android.support.v4.widget.NestedScrollView
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            app:layout_behavior="@string/appbar_scrolling_view_behavior">

            <TextView
                android:layout_width="match_parent"
                android:layout_height="wrap_content"
                android:text="@string/lorem_ipsum_long" />

        </android.support.v4.widget.NestedScrollView>

        <android.support.design.widget.FloatingActionButton
            android:id="@+id/overview_floating_action_button"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:layout_margin="16dp"
            android:clickable="true"
            android:src="https://stackoverflow.com/questions/32523188/@drawable/ic_add"
            app:layout_anchor="@id/overview_coordinator_layout"
            app:layout_anchorGravity="bottom|right|end"
            app:layout_behavior="@string/fab_onscroll_behavior" />

    </android.support.design.widget.CoordinatorLayout>

    <android.support.design.widget.NavigationView
        android:id="@+id/nvView"
        android:layout_width="wrap_content"
        android:layout_height="match_parent"
        android:layout_gravity="start"
        android:background="@android:color/white"
        app:headerLayout="@layout/nav_header"
        app:menu="@menu/navigationdrawer_main" />

</android.support.v4.widget.DrawerLayout>

That should sort it out!