anchor.diff:    }
   
     void _handleDayChanged(DateTime value) {
  -    HapticFeedback.vibrate();
  +    if (_vibrate)
  +      HapticFeedback.vibrate();
       setState(() {
         _selectedDate = value;
       });
  
positive.code: }
  
  class _DatePickerDialogState extends State<_DatePickerDialog> {
    @override
    void initState() {
      super.initState();
  
negative.code:   GlobalKey _pickerKey = new GlobalKey();
  
    void _handleModeChanged(_DatePickerMode mode) {
      if (_vibrate)
        HapticFeedback.vibrate();
      setState(() {
        _mode = mode;
      });
    }
  
    void _handleYearChanged(DateTime value) {
      if (_vibrate)
        HapticFeedback.vibrate();
      setState(() {
        _mode = _DatePickerMode.day;
        _selectedDate = value;
  