title: Android -purpose of useLevel in shape tag
body: <p>What is the purpose of android shape xml tag useLevel attribute ? This is in respect to a layer-list but should not matter. 
   From the <a href="http://developer.android.com/reference/android/graphics/drawable/GradientDrawable.html" rel="noreferrer">docs</a> i found the meanging of the useLevel tag:</p>
  
  <blockquote>
    <p>Indicates whether the drawable's level affects the way the gradient is drawn. </p>
  </blockquote>
  
  <p>So if i have the following xml snippet:</p>
  
  <pre><code>    &lt;?xml version="1.0" encoding="utf-8"?&gt;
  &lt;shape
      xmlns:android="http://schemas.android.com/apk/res/android"
      android:shape="ring"
      android:innerRadius="15dp"
      android:thickness="10dp"
      android:useLevel="false"&gt;
  
      &lt;solid android:color="#ababf2" /&gt;
  
      &lt;size
          android:height="50dp"
          android:width="50dp" /&gt;
  &lt;/shape&gt;
  </code></pre>
  
  <p>then with the useLevel=true, the ring is disabled.  It must be false for the ring to appear.  But what is the purpose of this attribute ? The docs are not clear. </p>