title: JavaFX RequestFocus
body: <p>I have an application, where the user can scan a barcode. Therefor I have a textfield, which gets the focus on first load. The application allows further actions for opening dialogs or triggering loading of data. 
  I need to set the focus to that field every time the user has finished this actions. 
  Is there any possibiltiy to capture all events on the main stage? 
  I have tried to add a listener to the focusProperty but this is just triggered on first load and on maximizing the window.</p>