title: Refresh imageview in listview without blocking the UI
body: <p>I have a <code>ListView</code> in which I am display Facebook friend's Image and name.Right now what I am doing is that I am showing 7 friends at once and have a load more button that displays next 7 and so on.   <img src="https://i.stack.imgur.com/4CZYN.png" alt="My Friend&#39;s Listview"></p>
  
  <p>Now what I want do is show all the names but with a default pic in the <code>ImageView</code> and refresh only if it is showing on the screen without blocking the UI. eg If user is seeing Mr X on the screen then only I get his picture and show it in the <code>ImageView</code> without blocking the UI.</p>