RawKeyboardListener({Key key, bool focused: false, ValueChanged<RawKeyEvent> onKey, Widget child })

Creates a widget that receives raw keyboard events.

For text entry, consider using a RawInput, which integrates with on-screen keyboards and input method editors (IMEs).

Source 

RawKeyboardListener({
  Key key,
  this.focused: false,
  this.onKey,
  this.child
}) : super(key: key) {
  assert(child != null);
}