title: Show overlay view above long scrollview to fill screen, when clicked on button at bottom of scrollview
body: <p>I have a scrollview, which is a bit long and easily goes beyond the screen height. Now at the bottom of the scrollview, there is a button and on the click of that button I perform some actions. While those actions are completed, I want to show an overlay mask, that fills the screen.</p>
  
  <p>OverlayLayout</p>
  
  <pre><code>&lt;LinearLayout&gt;
    &lt;ImageView&gt;&lt;/ImageView&gt;
    &lt;TextView&gt;Loading...&lt;/TextView&gt;
  &lt;/LinearLayout&gt;
  </code></pre>
  
  <p>The ScrollView layout looks as</p>
  
  <pre><code>&lt;ScrollView&gt;
    &lt;LinearLayout&gt;Main content&lt;/LinearLayout&gt;
  &lt;/ScrollView&gt;
  </code></pre>
  
  <p>I want that the overlay mask is rendered on the top of LinearLayout within ScrollView with respect to the screen and not the parent ScrollView.</p>