title: The following classes couldn't be instantiated
body: <p>On my homeactivity.xml it says:
  The following classes could not be instantiated:
  - android.support.design.widget.CoordinatorLayout (Open Class, Show Exception, Clear Cache)
  - android.support.design.widget.AppBarLayout (Open Class, Show Exception, Clear Cache)
  - android.support.design.widget.FloatingActionButton (Open Class, Show Exception, Clear Cache)</p>
  
  <p>Here is my code
      
  </p>
  
  <pre><code>&lt;android.support.design.widget.AppBarLayout
      android:layout_width="match_parent"
      android:layout_height="wrap_content"
      android:theme="@style/AppBarOverlay"&gt;
  
      &lt;android.support.v7.widget.Toolbar
          android:id="@+id/toolbar"
          android:layout_width="match_parent"
          android:layout_height="?attr/actionBarSize"
          android:background="#ff4747"
          app:popupTheme="@style/PopupOverlay" /&gt;
  
  
  &lt;include layout="@layout/content_home" /&gt;
  
  &lt;android.support.design.widget.FloatingActionButton
      android:id="@+id/fab"
      android:layout_width="wrap_content"
      android:layout_height="wrap_content"
      android:layout_gravity="bottom|end"
      android:layout_margin="@dimen/fab_margin"
      android:src="@android:drawable/ic_dialog_email"
      android:background="#001f9c" /&gt;
  
  &lt;/android.support.design.widget.AppBarLayout&gt;
  </code></pre>
  
  <p></p>
  
  <p>I don't know why this happened. Can someone please help?</p>