CollapsingToolbarLayout: Fix custom layout on top
<p>here's what I wanna do: I want to display a map in a CollapsingToolbarLayout, below the map should be a custom layout that contains a couple of controls. Below that is a RecyclerView. I want to be able scroll the custom layout as well as the RecyclerView but fix the custom layout at the top while the RecyclerView keeps scrolling. 
Here's an image of what I want to achieve (grey = map; red = custom layout; green = RecyclerView): 
<a href="https://i.stack.imgur.com/LBLQe.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/LBLQe.png" alt="enter image description here"></a></p>

<p>Here's what I have so far. It works well, except for that the custom layout (red) won't stop scrolling if it reaches the screen's top.  </p>

<pre><code>&lt;?xml version="1.0" encoding="utf-8"?&gt;
&lt;android.support.design.widget.CoordinatorLayout
    xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:mapbox="http://schemas.android.com/apk/res-auto"
    android:layout_width="match_parent"
    android:layout_height="match_parent"&gt;

    &lt;android.support.design.widget.AppBarLayout
        android:id="@+id/appBarLayout"
        android:layout_width="match_parent"
        android:layout_height="400dp"
        android:orientation="vertical"
        android:fitsSystemWindows="true"&gt;

        &lt;android.support.design.widget.CollapsingToolbarLayout
            android:id="@+id/collapsingToolbar"
            android:layout_width="match_parent"
            android:layout_height="match_parent"
            android:fitsSystemWindows="true"
            app:layout_scrollFlags="scroll|exitUntilCollapsed"
            app:theme="@style/ThemeOverlay.AppCompat.Dark.ActionBar"&gt;

            &lt;com.mapbox.mapboxsdk.maps.MapView
                android:id="@+id/map_view"
                android:layout_width="match_parent"
                android:layout_height="match_parent"
                app:layout_collapseMode="parallax"
                mapbox:zoom="12"
                mapbox:style_url="@string/style_light"
                mapbox:access_token="@string/access_token"&gt;
            &lt;/com.mapbox.mapboxsdk.maps.MapView&gt;

        &lt;/android.support.design.widget.CollapsingToolbarLayout&gt;

    &lt;/android.support.design.widget.AppBarLayout&gt;

    &lt;LinearLayout
        android:id="@+id/content"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:orientation="vertical"
        app:layout_behavior="@string/appbar_scrolling_view_behavior"&gt;

        &lt;include layout="@layout/current_activity"&gt;&lt;/include&gt;

        &lt;android.support.v7.widget.RecyclerView
            android:id="@+id/activity_list"
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:layout_marginTop="16dp"&gt;

        &lt;/android.support.v7.widget.RecyclerView&gt;

    &lt;/LinearLayout&gt;
&lt;/android.support.design.widget.CoordinatorLayout&gt;
</code></pre>

<p>What's the easiest way to achieve this behavior?</p>