title: Show/hide BottomNavigationView on scroll in CoordinatorLayout with AppBarLayout
body: <p>I am trying to use both <code>AppBarLayout</code> and <code>BottomNavigationLayout</code> in a single <code>CoordinatorLayout</code> and I'm having difficulties hiding the <code>BottomNavigationLayout</code> as required by the <a href="https://material.io/guidelines/components/bottom-navigation.html#bottom-navigation-behavior" rel="noreferrer">material guideline</a>.</p>
  
  <p>I mean something like this:</p>
  
  <pre><code>&lt;android.support.design.widget.CoordinatorLayout xmlns:android="http://schemas.android.com/apk/res/android"
      xmlns:app="http://schemas.android.com/apk/res-auto"
      android:orientation="vertical"
      android:layout_width="match_parent"
      android:layout_height="match_parent"
      android:fitsSystemWindows="false"&gt;
  
      &lt;android.support.design.widget.AppBarLayout
          android:id="@+id/app_bar"
          android:layout_width="match_parent"
          android:layout_height="wrap_content"
          app:layout_insetEdge="top"
          android:theme="@style/AppTheme.AppBarOverlay"&gt;
  
          &lt;android.support.v7.widget.Toolbar
              android:id="@+id/toolbar"
              android:layout_width="match_parent"
              android:layout_height="?attr/actionBarSize"
              app:popupTheme="@style/AppTheme.PopupOverlay"
              app:layout_scrollFlags="scroll|enterAlways"/&gt;
      &lt;/android.support.design.widget.AppBarLayout&gt;
  
  
      &lt;android.support.design.widget.BottomNavigationView
          android:id="@+id/bottom_nav"
          android:layout_width="match_parent"
          android:layout_height="56dp"
          android:layout_gravity="bottom"
          app:menu="@menu/menu_bottom_navigation"/&gt;
  
      &lt;FrameLayout
          android:id="@+id/content_container"
          android:layout_width="match_parent"
          android:layout_height="wrap_content"
          android:layout_gravity="top"
          app:layout_behavior="@string/appbar_scrolling_view_behavior"/&gt;
  
  &lt;/android.support.design.widget.CoordinatorLayout&gt;
  </code></pre>
  
  <p>As you can see, I also have a <code>FrameLayout</code> that's used to contain a fragment with the actual content. Currently there are no default/built-in behaviors for the <code>BottomNavigationView</code> - neither for the view itself, nor for its siblings. The existing <code>appbar_scrolling_view_behavior</code> handles the content view in coordination with the appbar but ignores other siblings. </p>
  
  <p>I am looking for a solution to hide and show both the appbar and the bottom navigation view on scroll.</p>