title: How can I add the new "Floating Action Button" between two widgets/layouts
body: <p>I guess you have seen the new Android design guidelines, with the new "Floating Action Button" a.k.a "FAB"</p>
  
  <p>For instance this pink button:</p>
  
  <p><img src="https://i.stack.imgur.com/xCxE0.png" alt="enter image description here"></p>
  
  <p>My question sounds stupid, and I have already tried a lot of things, but what is the best way to put this button at the intersection of two layouts?</p>
  
  <p>In the above exemple, this button is perfectly placed between what we can imagine to be an ImageView and a relativeLayout.</p>
  
  <p>I have already tried a lot of tweaks, but I am convinced there is a proper way to do it.</p>