title: Android Studio app crashes on launch when using ?colorVariant in xml drawable
body: <p>I have a shape in one of my xml drawables that uses the styles of my themes.xml file:</p>
  <pre><code>&lt;shape android:shape=&quot;oval&quot;&gt;
      &lt;gradient
          android:gradientRadius=&quot;134dp&quot;
          android:startColor=&quot;?colorPrimary&quot;
          android:centerColor=&quot;#000000&quot;
          android:endColor=&quot;#000111&quot;
          android:type=&quot;radial&quot; /&gt;
  &lt;/shape&gt;
  </code></pre>
  <p>As you can see startColor  uses the colorPrimary attribute. However, when I launch the app in the Android Studio emulator it crashes without build error. When I replace ?colorPrimary by a random hex color everything seems to be fine. I'm using API 24 and as far as I know you can use ?colorVariant for &gt;API 21. Not sure what I'm doing wrong here.</p>