title: How to show a widget only when user is scrolling?
body: <p>I want to hide buttons on screen and show them after user starts scrolling till for the 5 seconds from the last scroll.</p>
  
  <p>I've wrapped my <code>SingleChildScrollView</code> with <code>GestureDetector</code> and change the visibility value from <code>onTap</code> callback to hide my buttons with <code>Visibility</code> widget. However, there is no event like onScroll on <code>GestureDetector</code>. </p>
  
  <p>Is there anyone who succesfully implement that effect or is there any built-in animation for what I'm trying to achieve?</p>