title: Android Toolbar disappear during scrolling with Coordinatorlayout
body: <p>a strange thing happened when I try to implement the toolbar with the <code>Coordinatorlayout</code>.</p>
  
  <ol>
  <li>everything seems ok when I scroll down and scroll up the <code>toolbar</code> show correctly</li>
  </ol>
  
  <p><img src="https://i.stack.imgur.com/eRQK2.png" alt="enter image description here"></p>
  
  <ol start="2">
  <li>however after I scroll down to a certain level the screen became </li>
  </ol>
  
  <p><img src="https://i.stack.imgur.com/xUi84.png" alt="enter image description here"></p>
  
  <p>The XML is below, any idea of it, thanks?</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:layout_width="match_parent" android:layout_height="match_parent"&gt;
  
  &lt;android.support.v7.widget.RecyclerView
      android:id="@+id/list"
      android:layout_width="match_parent"
      android:layout_height="match_parent"
      app:layout_behavior="@string/appbar_scrolling_view_behavior"
      /&gt;
  
  &lt;android.support.design.widget.AppBarLayout
      android:id="@+id/appbar"
      android:layout_width="match_parent"
      android:layout_height="wrap_content"&gt;
  
      &lt;android.support.v7.widget.Toolbar
          android:id="@+id/toolbar"
          android:layout_width="match_parent"
          android:layout_height="?attr/actionBarSize"
          android:background="?attr/colorPrimary"
          android:theme="@style/ThemeOverlay.AppCompat.Dark.ActionBar"
          app:layout_scrollFlags="scroll|enterAlways"
          /&gt;
  
  &lt;/android.support.design.widget.AppBarLayout&gt;
  </code></pre>
  
  <p></p>