如何從另一個 Dart 文件中調用函數

Question

我有這個處理我的日期和時間選擇器小部件的功能......下面的代碼......

Future selectDayAndTimeL(BuildContext context) async {
    DateTime? selectedDay = await showDatePicker(
        context: context,
        initialDate: DateTime.now(),
        firstDate: DateTime(2021),
        lastDate: DateTime(2030),
        builder: (BuildContext context, Widget? child) => child!);

    TimeOfDay? selectedTime = await showTimePicker(
      context: context,
      initialTime: TimeOfDay.now(),
    );

    if (selectedDay != null && selectedTime != null) {
      //a little check
    }
    setState(() {
      selectedDateAndTime = DateTime(
        selectedDay!.year,
        selectedDay!.month,
        selectedDay!.day,
        selectedTime!.hour,
        selectedTime!.minute,
      );
      // _selectedDate = _selectedDay;
    });
    // print('...');
  }

Answer 1

setState 告訴有狀態小部件根據更改的數據重新渲染。 在您的情況下，您正在更改selectedDateAndTime<\/code>並使用更新的數據重新構建小部件。

如果您想從“遠程”功能更新\/重建小部件，您需要使用回調。

Future selectDayAndTimeL(BuildContext context,Function(DateTime time) onDateTimeSelected)  async {
    DateTime? selectedDay = await showDatePicker(
        context: context,
        initialDate: DateTime.now(),
        firstDate: DateTime(2021),
        lastDate: DateTime(2030),
        builder: (BuildContext context, Widget? child) => child!);

    TimeOfDay? selectedTime = await showTimePicker(
      context: context,
      initialTime: TimeOfDay.now(),
    );

    if (selectedDay != null && selectedTime != null) {
      //a little check
    }
    // call the callback here with your calculated data
    onDateTimeSelected(
      DateTime(
        selectedDay!.year,
        selectedDay!.month,
        selectedDay!.day,
        selectedTime!.hour,
        selectedTime!.minute,
      ),
    );
  }

Answer 2

我猜你最初有一個Statefull<\/code>小部件，它可能看起來像這樣：

class OriginalWidget extends StatefulWidget {
  @override
  _OriginalWidgetState createState() => _OriginalWidgetState();
}

class _OriginalWidgetState extends State<OriginalWidget> {

  DateTime? _selectedDate;
  DateTime? selectedDateAndTime;

  Future selectDayAndTimeL(BuildContext context) async {
    DateTime? selectedDay = await showDatePicker(
        context: context,
        initialDate: DateTime.now(),
        firstDate: DateTime(2021),
        lastDate: DateTime(2030),
        builder: (BuildContext context, Widget? child) => child!);

    TimeOfDay? selectedTime = await showTimePicker(
      context: context,
      initialTime: TimeOfDay.now(),
    );

    if (selectedDay != null && selectedTime != null) {
      //a little check
    }
    setState(() {
      selectedDateAndTime = DateTime(
        selectedDay!.year,
        selectedDay!.month,
        selectedDay!.day,
        selectedTime!.hour,
        selectedTime!.minute,
      );
      // _selectedDate = _selectedDay;
    });
    // print('...');
  }

  @override
  Widget build(BuildContext context) {
    return FlatButton(
          onPressed: () => selectDayAndTimeL(context));
  } 
}