title: Intercept barcode scanning event
body: <p>I'm developing an application that will be installed in mobile devices with integrated barcode scanner.
  In my page there are different types of widget, included a not visible Entry that I want to use temporary to store the scanned barcode value.
  The problem is that the user can tap and interact with all the widgets in the page and, in an unknown moment, he can scan a barcode.
  I want to force the focus in this invisible Entry or intercept the text typed (because a barcode scan is like a keyboard typing). How I can do that?
  I'm developing with Xamarin.Forms with Prism framework for MVVM.</p>
  
  <p>N.B. = The barcode scanning is not with the cam.</p>