title: Card view material ripple?
body: <p>I'm developing a material design interface. I have cards that I want to have the ripple effect when clicked. I've done what google says and nothing happens. Here's my code:</p>
  
  <pre><code>&lt;android.support.v7.widget.CardView
              xmlns:card_view="http://schemas.android.com/apk/res-auto"
              android:id="@+id/card_view"
              android:layout_gravity="center"
              android:clickable="true"
              android:layout_width="fill_parent"
              android:layout_height="250dp"
              android:elevation="5dp"
              android:background="?android:selectableItemBackground"&gt;
              &gt;
  
              &lt;ImageView 
                  android:id="@+id/blue_image"
                  android:src="@drawable/blue"
                  android:layout_alignParentTop="true"
                  android:layout_width="fill_parent"
                  android:layout_height="200dp"
                  android:elevation="8dp"
              /&gt;
  
              &lt;TextView
                  android:id="@+id/text_view"
                  android:layout_width="match_parent"    
                  android:layout_height="50dp"
                  android:layout_alignParentBottom="true"
                  android:text="And this is a blue card!" 
                  android:elevation="10dp"
                  /&gt;
  </code></pre>