title: Card_view material design
body: <p>I am trying to use <code>card_view</code>. But it keeps giving an error.</p>
  
  <blockquote>
    <p>Error:(13) No resource identifier found for attribute `'cardCornerRadius' in package 'com.google.example.test_app'</p>
  </blockquote>
  
  <pre><code>&lt;RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
      xmlns:tools="http://schemas.android.com/tools"
      android:layout_width="match_parent"
      android:layout_height="match_parent"
      android:paddingLeft="@dimen/activity_horizontal_margin"
      android:paddingRight="@dimen/activity_horizontal_margin"
      android:paddingTop="@dimen/activity_vertical_margin"
      android:paddingBottom="@dimen/activity_vertical_margin"
      android:background="#610B0B"
      tools:context=".MyActivity"
      android:id="@+id/myactivity "&gt;
      &lt;android.support.v7.widget.CardView
          xmlns:card_view="http://schemas.android.com/apk/res-auto"
          android:id="@+id/card_view"
          android:layout_width="200dp"
          android:layout_height="200dp"
          android:layout_gravity="center"
          android:background="#fff"
          card_view:cardCornerRadius="4dp"&gt;
          &lt;TextView
          android:id="@+id/my_textview"
          android:layout_width="wrap_content"
          android:layout_height="wrap_content"
          android:text="@string/next"
          android:background="#fff"
          android:elevation="5dp" /&gt;
      &lt;/android.support.v7.widget.CardView&gt;
  &lt;/RelativeLayout&gt;
  </code></pre>
  
  <p>What am I doing wrong here?</p>