title: android.support.v7.cardview:cardBackgroundColor doesn't work
body: <p>I have the following XML code in a resource file, which represents an item in a RecyclerView:</p>
  
  <pre><code>&lt;?xml version="1.0" encoding="utf-8"?&gt;
  &lt;android.support.v7.widget.CardView xmlns:android="http://schemas.android.com/apk/res/android"
      xmlns:android.support.v7.cardview="http://schemas.android.com/tools"
      android:layout_width="match_parent"
      android:layout_height="wrap_content"
      android.support.v7.cardview:cardBackgroundColor="#9e9e9e"
      android.support.v7.cardview:cardElevation="7dp"&gt;
  
      &lt;LinearLayout
          android:layout_width="match_parent"
          android:layout_height="match_parent"
          android:orientation="vertical"&gt;
          &lt;LinearLayout
              android:layout_width="match_parent"
              android:layout_height="match_parent"
              android:background="@android:color/transparent"
              android:orientation="vertical"&gt;
              &lt;ImageView
                  android:id="@+id/type"
                  android:layout_width="15dp"
                  android:layout_height="15dp"
                  android:layout_gravity="end" /&gt;
              &lt;LinearLayout
                  android:layout_width="match_parent"
                  android:layout_height="wrap_content"
                  android:orientation="horizontal"&gt;
                  &lt;TextView
                      android:id="@+id/field_name"
                      android:layout_width="0dp"
                      android:layout_height="wrap_content"
                      android:layout_weight="1"
                      android:padding="2dp"
                      android:textColor="#000000"
                      android:textSize="20sp"
                      android:typeface="monospace" /&gt;
                  &lt;LinearLayout
                      android:layout_width="15dp"
                      android:layout_height="match_parent" /&gt;
              &lt;/LinearLayout&gt;
              &lt;LinearLayout
                  android:id="@+id/main_recyclerview_item_actions"
                  android:layout_width="match_parent"
                  android:layout_height="wrap_content"
                  android:gravity="end"
                  android:visibility="gone"&gt;
                  &lt;Button
                      android:id="@+id/delete"
                      android:layout_width="wrap_content"
                      android:layout_height="wrap_content"
                      android:text="@string/delete"
                      android:textColor="@color/colorAccent"
                      style="@style/Widget.AppCompat.Button.Borderless"/&gt;
              &lt;/LinearLayout&gt;
          &lt;/LinearLayout&gt;
      &lt;/LinearLayout&gt;
  &lt;/android.support.v7.widget.CardView&gt;
  </code></pre>
  
  <p>The problem is that the CardView is never get the color: 9e9e9e as the following image:
  The color is white not 9e9e9e</p>
  
  <p><a href="https://i.stack.imgur.com/OFl3S.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/OFl3S.png" alt="enter image description here"></a></p>
  
  <p>Where is the problem in the code? And how can I solve this problem?</p>