XML : Views appearing on top of collapsing toolbar

EDIT: Problem solved. See Blackbelt's comment

I've been trying to implement the collapsing toolbar into my project, sticking to an example provided by Google. I've gotten it to work for the most part, but views are appearing on top of the toolbar rather than below them.

Below, I've pasted the XML code for the activity that hosts the toolbar.

  <android.support.design.widget.CoordinatorLayout  xmlns:android="http://schemas.android.com/apk/res/android"  xmlns:app="http://schemas.android.com/apk/res-auto"  xmlns:tools="http://schemas.android.com/tools"  android:layout_width="match_parent"  android:layout_height="match_parent"  android:fitsSystemWindows="true"    tools:context="android.jochemkleine.com.popularmovies.ui.MovieDetailActivity"  android:background="#57ffffff">          <android.support.design.widget.AppBarLayout          android:id="@+id/app_bar"          android:layout_width="match_parent"          android:layout_height="@dimen/app_bar_height"          android:fitsSystemWindows="true"          android:theme="@style/AppTheme.AppBarOverlay">            <android.support.design.widget.CollapsingToolbarLayout              android:id="@+id/toolbar_layout"              android:layout_width="match_parent"              android:layout_height="match_parent"              android:fitsSystemWindows="true"              app:contentScrim="?attr/colorPrimary"              app:layout_scrollFlags="scroll|exitUntilCollapsed">                <ImageView                  android:layout_width="match_parent"                  android:layout_height="match_parent"                  android:scaleType="fitXY"                  android:fitsSystemWindows="true"                  app:layout_collapseMode="parallax"                  android:id="@+id/toolbarImage"                  />                <android.support.v7.widget.Toolbar                  android:id="@+id/toolbar"                  android:layout_width="match_parent"                  android:layout_height="?attr/actionBarSize"                  app:layout_collapseMode="pin"                  app:popupTheme="@style/AppTheme.PopupOverlay"/>            </android.support.design.widget.CollapsingToolbarLayout>      </android.support.design.widget.AppBarLayout>        <FrameLayout          android:layout_width="match_parent"          android:layout_height="match_parent"          android:id="@+id/item_detail_container">        </FrameLayout>        <android.support.design.widget.FloatingActionButton          android:layout_width="wrap_content"          android:layout_height="wrap_content"          android:layout_margin="@dimen/fab_margin"          android:src="@android:drawable/btn_star_big_off"          app:layout_anchor="@id/app_bar"          app:layout_anchorGravity="bottom|end"          android:scaleType="center"          app:backgroundTint="#ffffff"/>    

Note that the FrameLayout with id item_detail_container will contain a fragment. Said fragment uses to the following XML file:

  <?xml version="1.0" encoding="utf-8"?>  <android.support.v4.widget.NestedScrollView  xmlns:android="http://schemas.android.com/apk/res/android"  xmlns:app="http://schemas.android.com/apk/res-auto"  xmlns:tools="http://schemas.android.com/tools"  android:layout_width="match_parent"  android:layout_height="match_parent"    app:layout_behavior="@string/appbar_scrolling_view_behavior"  tools:showIn="@layout/activity_movie_details"  tools:context="android.jochemkleine.com.popularmovies.ui.m"  >    <LinearLayout      android:layout_width="match_parent"      android:layout_height="match_parent"      android:orientation="vertical">        <TextView          android:layout_width="wrap_content"          android:layout_height="wrap_content"          android:text="TEST TEXTVIEW"          />    </LinearLayout>    

Note that right now, the LinearLayout in this XML file serves no purpose at all, because there is only one TextView present. It will however be of use later, as NestedScrollView can only host one direct child.

I am fairly sure that the fault lies somewhere within the first XML file, likely with the use of the FrameLayout. What baffles me is that the Google example does it almost exactly the same way, the only difference is that they include a layout, instead of using a FrameLayout.

Thanks in advance; any and all help is appreciated.