title: Android RecyclerView in ConstraintLayout doesn't scroll
body: <p>I have a recyclerView inside a constraint layout and I cannot make it scroll, the list just continues below the screen without scroll possibility. If I turn the layout into relative layout the scroll works fine.</p>
  
  <p>how can I get it to scroll?</p>
  
  <p>the the following XML shows my layout, the recycler view is in the bottom.  the layout has an image and description at the top of the screen. this screen setup takes 30% of the screen. followed by and a separator and the recycler view that should take the rest of the screen and that cannot scroll </p>
  
  <pre><code>&lt;?xml version="1.0" encoding="utf-8"?&gt;
  &lt;android.support.constraint.ConstraintLayout
      xmlns:android="http://schemas.android.com/apk/res/android"
      xmlns:app="http://schemas.android.com/apk/res-auto"
      android:layout_width="match_parent"
      android:layout_height="match_parent"
      android:background="@color/gradient_top"&gt;
  
     &lt;android.support.v7.widget.AppCompatImageView
          android:id="@+id/imageViewLock"
          android:layout_width="80dp"
          android:layout_height="80dp"
          android:layout_marginBottom="10dp"
          android:layout_marginTop="16dp"
          app:layout_constraintBottom_toTopOf="@+id/textViewPermissionsTitle"
          app:layout_constraintLeft_toLeftOf="parent"
          app:layout_constraintRight_toRightOf="parent"
          app:layout_constraintTop_toTopOf="parent"
          app:srcCompat="@drawable/ic_phone_lock"/&gt;
  
      &lt;TextView
          android:id="@+id/textViewPermissionsTitle"
          android:layout_width="wrap_content"
          android:layout_height="wrap_content"
          android:layout_marginBottom="8dp"
          android:gravity="center"
          android:paddingLeft="24dp"
          android:paddingRight="24dp"
          android:text="@string/allow_permissions"
          android:textColor="@color/white"
          android:textSize="@dimen/description_text_size"
          app:layout_constraintBottom_toTopOf="@+id/guideline1"
          app:layout_constraintLeft_toLeftOf="parent"
          app:layout_constraintRight_toRightOf="parent"/&gt;
  
      &lt;android.support.constraint.Guideline
          android:id="@+id/guideline1"
          android:layout_width="match_parent"
          android:layout_height="wrap_content"
          android:orientation="horizontal"
          app:layout_constraintGuide_percent="0.3"/&gt;
  
  
      &lt;View
          android:id="@+id/viewSeparator"
          android:layout_width="match_parent"
          android:layout_height="0.7dp"
          android:layout_marginTop="10dp"
          android:background="@color/bright_blue"
          app:layout_constraintLeft_toLeftOf="parent"
          app:layout_constraintRight_toRightOf="parent"
          app:layout_constraintTop_toTopOf="@+id/guideline1"/&gt;
  
      &lt;android.support.v7.widget.RecyclerView
          android:id="@+id/recyclerViewPermissions"
          android:layout_width="match_parent"
          android:layout_height="wrap_content"
          android:scrollbarSize="1dp"
          android:scrollbarThumbVertical="@color/white"
          android:scrollbars="vertical"
          app:layout_constraintTop_toBottomOf="@+id/viewSeparator" /&gt;
  
  
  &lt;/android.support.constraint.ConstraintLayout&gt;
  </code></pre>