你可以使用syncfusion_flutter_datepicker库，它有一个selectionChanged回调函数，你可以通过它来限制可选择的日期，下面的代码片段展示了如何将范围限制在从选定的_start天开始的14天内。

class Home extends StatefulWidget {
  const Home({super.key});

  @override
  State<Home> createState() => _HomeState();
}

class _HomeState extends State<Home> {
  final DateTime _minDate = DateTime.now();
  DateTime _maxDate = DateTime.now().add(const Duration(days: 365));

  final Duration _duration = const Duration(days: 14);

  DateTime _start = DateTime.now();

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      body: SafeArea(
          child: SfDateRangePicker(
        minDate: _minDate,
        maxDate: _maxDate,
        selectionMode: DateRangePickerSelectionMode.range,
        onSelectionChanged: (DateRangePickerSelectionChangedArgs args) {
          if (args.value is PickerDateRange) {
            _start = (args.value as PickerDateRange).startDate!;
            setState(() {
              // limit the maxDate to 14 days from selected date
              _maxDate = _start.add(_duration);
            });
          }
        },
      )),
    );
  }
}

有关更多自定义信息，请参阅docs。