title: Ripple effect does not work in RelativeLayout
body: <p>I'm trying to implement ripple effect in a <code>RelativeLayout</code> on API 22 but it doesn't show up. However the same ripple works in a <code>Button</code>.</p>
  
  <p>The code for my ripple drawable is as follows:</p>
  
  <pre><code>&lt;?xml version="1.0" encoding="utf-8"?&gt;
  &lt;ripple xmlns:android="http://schemas.android.com/apk/res/android"
      android:color="#d1c4e9"&gt;
      &lt;item android:id="@android:id/mask"
          android:drawable="@android:color/white" /&gt;
      &lt;item android:drawable="@drawable/rect"/&gt;
  &lt;/ripple&gt;
  </code></pre>
  
  <p>Code for Relative Layout is as follows:</p>
  
  <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"
      tools:context=".MainActivity"
      android:background="@drawable/ripple"&gt;
  &lt;/RelativeLayout&gt;
  </code></pre>
  
  <p>After this the ripple is set as a background on <code>Button</code> and <code>RelativeLayout</code>. The ripple on button works great but it doesn't show up on the <code>RelativeLayout</code> at all.</p>
  
  <p>Can anyone tell me what am I doing wrong?</p>