flutter - 如何设置一个日期选择器选择的日期是 flutter 另一个日期选择器的第一日期

Question

我有两个日期选择器字段契约(Contract)开始日期和契约(Contract)结束日期。当我选择契约(Contract)开始日期时，将选择第一个日期选择器的日期作为契约(Contract)结束日期的初始值或第一个日期。

在这里，我有两个日期选择器的代码。

  Widget _buildContractBeginDate() {
    return DateTimeField(
      format: format,
      autocorrect: true,
      autovalidate: false,
      controller: _contractBeginDate,
      readOnly: true,
      validator: (date) => (date == null || _contractBeginDate.text == '')
          ? 'Please enter valid date'
          : null,
      decoration: InputDecoration(
          labelText: "Contract Begin Date",
          hintText: "Contract Begin Date",
          prefixIcon: Icon(
            FontAwesomeIcons.calendar,
            size: 24,
          )),
      onShowPicker: (context, currentValue) {
        return showDatePicker(
          context: context,
          firstDate: DateTime(1900),
          initialDate: currentValue ?? DateTime.now(),
          lastDate: DateTime(2022),
        );
      },
    );
  }

  Widget _buildContractEndDate() {
    return DateTimeField(
      format: format,
      autocorrect: true,
      autovalidate: false,
      controller: _contractEndDate,
      readOnly: true,
      validator: (date) => (date == null || _contractEndDate.text == '')
          ? 'Please enter valid date'
          : null,
      decoration: InputDecoration(
          labelText: "Contract End Date",
          hintText: "Contract End Date",
          prefixIcon: Icon(
            FontAwesomeIcons.calendar,
            size: 24,
          )),
      onShowPicker: (context, currentValue) {
        return showDatePicker(
            context: context,
            firstDate: DateTime(1900),
            initialDate: currentValue ?? DateTime.now(),
            lastDate: DateTime(2022));
      },
    );
  }

Answer 1

我创建了一个与您的演示有些相似的演示，请引用:

TL; DR:使用ValueNotifier<DateTime>并从第一个日期选择器更新其值，并始终使用该通知程序的值作为第二个日期选择器的第一个日期。这样，您将始终获得更新的日期。

Run code on Dartpad

import 'package:flutter/material.dart';

void main() {
  runApp(
    MaterialApp(home: MyApp()),
  );
}

class MyApp extends StatefulWidget {
  @override
  _MyAppState createState() => _MyAppState();
}

class _MyAppState extends State<MyApp> with SingleTickerProviderStateMixin {
  ValueNotifier<DateTime> _dateTimeNotifier = ValueNotifier<DateTime>(DateTime.now());
  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(title: Text('Demo')),
      body: Column(
        children: <Widget>[
          _buildContractBeginDate(context, _dateTimeNotifier),
          _buildContractEndDate(context, _dateTimeNotifier),          
        ],
      ),
    );
  }
}

Widget _buildContractBeginDate(BuildContext context, ValueNotifier<DateTime> _dateTimeNotifier) {
     return RaisedButton(
       child: Text('Begin Date'), 
      onPressed: () => showDatePicker(
            context: context,
            firstDate: DateTime(1900),
            initialDate: _dateTimeNotifier.value,
            lastDate: DateTime(2022), 
            ).then((DateTime dateTime) => _dateTimeNotifier.value = dateTime),
    );
  }

  Widget _buildContractEndDate(BuildContext context,ValueNotifier<DateTime> _dateTimeNotifier) {
    return RaisedButton(
       child: Text('End Date'), 
      onPressed: () {
        return showDatePicker(
            context: context,
            firstDate: _dateTimeNotifier.value,
            initialDate: _dateTimeNotifier.value ?? DateTime.now(),
            lastDate: DateTime(2022));
      },
    );
  }

希望对您有所帮助，如有任何疑问，请发表评论。