title: Detect back button but don't dismiss dialogfragment
body: <p>I have a dialogfragment for a floating dialog which includes a special keyboard that pops up when a user presses inside an EditText field (the normal IME is stopped from being displayed).</p>
  
  <p>I would like the keyboard to be dismissed (visibility = GONE) when the user presses the back button (just as with a normal IME service) but the dialog to remain visible. However, there does not appear to be a way to do this as far as I can see from my fairly extensive reading on SO and elsewhere.</p>
  
  <p>If I set the dialog to be non-cancelable then I don't get notified by onCancel() or onDismiss() because the dialog isn't cancelable.</p>
  
  <p>If I set the dialog to be cancelable then I get notified, but the dialog is dismissed.</p>
  
  <p>I can't attach an onKeyListener to the dialog in the fragment because it is replaced by the system so that the fragment can handle the dialog's life cycle.</p>
  
  <p>Is there any way to do this? Or has access to the detection of key events been entirely fenced off for the purposes of the Fragment system?</p>