title: ViewDragHelper: how to use it?
body: <p>In the Google IO 2013, Google has announced a new version of the Support Library, which includes <code>ViewDragHelper</code> class.
  I saw the docs, but I couldn't find any sample of usage for this class.</p>
  
  <p>For example, a very typical situation: I have a custom view, which extends from <code>FrameLayout</code> and allows to drag some of the <code>View</code>s inside. For example, let it be a <code>Button</code>. I override <code>onTouchEvent()</code> and <code>onInterceptTouchEvent()</code> within my custom view, and if the button of the rect contains the touch coordinates and this is not a simple click, then I start to drag.</p>
  
  <p>So, what I must do with <code>ViewDragHelper</code> to get that? The clicks to the <code>Button</code> should process correctly.</p>