title: Can't scroll completely down in ViewPager with NestedScrollView in CollapsedToolBarLayout
body: <p>I'm creating a fragment with a collapsing Toolbar Layout using a ViewPager. This is the XML for the Layout:</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:tools="http://schemas.android.com/tools"
      android:id="@+id/htab_maincontent"
      android:layout_width="match_parent"
      android:layout_height="match_parent"
      android:fitsSystemWindows="true"
      tools:context=".activities.AppActivity"&gt;
  
      &lt;android.support.design.widget.AppBarLayout
          android:id="@+id/htab_appbar"
          android:layout_width="match_parent"
          android:layout_height="wrap_content"
          android:background="?attr/colorPrimary"
          android:fitsSystemWindows="true"
          android:backgroundTint="@color/completeWhite"&gt;
  
          &lt;android.support.design.widget.CollapsingToolbarLayout
              android:id="@+id/htab_collapse_toolbar"
              android:layout_width="match_parent"
              android:layout_height="420dp"
              android:fitsSystemWindows="true"
              app:contentScrim="@color/completeWhite"
              app:layout_scrollFlags="scroll|exitUntilCollapsed|snap"
              app:titleEnabled="false"&gt;
  
              &lt;RelativeLayout
                  android:id="@+id/brand_page"
                  android:layout_width="match_parent"
                  android:layout_height="wrap_content"
                  app:layout_collapseMode="parallax"
                  android:paddingTop="24dp"
                  android:layout_marginTop="?attr/actionBarSize"&gt;
  
                  //Lots of images and texts that are collapsed
  
              &lt;/RelativeLayout&gt;
  
              &lt;android.support.v7.widget.Toolbar
                  android:id="@+id/htab_toolbar"
                  android:layout_width="match_parent"
                  android:layout_height="?attr/actionBarSize"
                  android:layout_gravity="top"
                  android:layout_marginBottom="75dp"
                  app:layout_collapseMode="pin"
                  app:popupTheme="@style/ThemeOverlay.AppCompat.Light"/&gt;
  
              &lt;android.support.design.widget.TabLayout
                  android:id="@+id/htab_tabs"
                  android:layout_width="match_parent"
                  android:layout_height="wrap_content"
                  android:layout_gravity="bottom"
                  app:tabIndicatorColor="@android:color/white"
                  app:tabSelectedTextColor="@color/lightGreen"
                  app:tabTextColor="@color/grey"/&gt;
  
          &lt;/android.support.design.widget.CollapsingToolbarLayout&gt;
  
      &lt;/android.support.design.widget.AppBarLayout&gt;
  
      &lt;io.brandie.brandie.custom.NoSwipeViewPager
          android:id="@+id/htab_viewpager"
          android:layout_width="match_parent"
          android:layout_height="match_parent"
          app:layout_behavior="@string/appbar_scrolling_view_behavior"
          android:layout_marginBottom="@dimen/spacing_giant"
          android:background="@color/white"/&gt;
  
  &lt;/android.support.design.widget.CoordinatorLayout&gt;
  </code></pre>
  
  <p>The viewPager is filled with fragments that use a gridview to display different cards, this is the xml for the Fragment of the first tab:</p>
  
  <pre><code>&lt;?xml version="1.0" encoding="utf-8"?&gt;
  &lt;android.support.v4.widget.NestedScrollView
      android:id="@+id/NestedScroll"
      xmlns:android="http://schemas.android.com/apk/res/android"
      android:layout_width="match_parent"
      android:layout_height="match_parent"
      xmlns:app="http://schemas.android.com/apk/res-auto"
      android:fillViewport="true"
      android:fitsSystemWindows="true"
      android:layout_gravity="fill_vertical"
      android:theme="@style/ThemeOverlay.AppCompat.Dark.ActionBar"&gt;
  
      &lt;FrameLayout xmlns:android="http://schemas.android.com/apk/res/android"
          xmlns:tools="http://schemas.android.com/tools"
          android:id="@+id/all_campaigns_frame"
          android:layout_width="match_parent"
          android:layout_height="match_parent"
          tools:context="io.brandie.brandie.fragments.AllCampaignsFragment"&gt;
  
          &lt;GridView xmlns:android="http://schemas.android.com/apk/res/android"
              android:id="@+id/all_campaigns_grid"
              android:descendantFocusability="blocksDescendants"
              android:layout_width="wrap_content"
              android:layout_height="wrap_content"
              android:numColumns="2"
              android:verticalSpacing="10dp"
              android:horizontalSpacing="10dp"
              android:stretchMode="columnWidth"
              android:gravity="center" /&gt;
  
      &lt;/FrameLayout&gt;
  
  &lt;/android.support.v4.widget.NestedScrollView&gt;
  </code></pre>
  
  <p>With this I can scroll down anywhere on the screen to make the toolbar collapse and the view-pager expand. The problem is, when the tool-bar is completely collapsed and only the tabs are showing, I can't scroll the viewPager anymore. Since it holds a gridView with a lot of items, it results in that I can't scroll through them all, since the scroll just "stops".</p>
  
  <p>I want it to look like <a href="https://cdn-images-1.medium.com/max/800/0*O5QqNPUVw6qE2lgY.gif" rel="nofollow noreferrer">this</a></p>
  
  <p>But instead, when the toolbar is collapsed, I can't scroll the viewPager down anymore. I can however scroll it up to reveal the toolbar again, that works without issues. I am using Android API 16, is that an issue?</p>
  
  <p>How do I fix this very irritating problem?</p>
  
  <p>EDIT:
  If I remove the NestedScrollView from the fragment XML, the collapsed Toolbar only collapses if I scroll on the toolbar. If I scroll the ViewPager, I can scroll through all content correctly, but the toolbar doesn't collapse.</p>