Flutter 获取周末和月份

Question

我需要在 Flutter 中获取周末的日期（仅周五和周六）以及该月的第一天和最后一天的日期

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这是我周末尝试过的方法，但它不起作用\xc2\xb4t：

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      var dateuntilfriday = DateTime.now();\n\n      getFriday() async {\n        if (dateuntilfriday.weekday == DateTime.friday) {\n          dateuntilfriday.add(Duration(days: 0));\n          print("1 Executed");\n        } else if (dateuntilfriday.weekday == DateTime.saturday) {\n          dateuntilfriday.subtract(Duration(days: 1));\n          print("2 Executed");\n        } else if (dateuntilfriday.weekday == DateTime.sunday) {\n          dateuntilfriday.subtract(Duration(days: 2));\n          print("3 Executed");\n        } else if (dateuntilfriday.weekday == DateTime.monday) {\n          dateuntilfriday.add(Duration(days: 4));\n          print("4 Executed");\n        } else if (dateuntilfriday.weekday == DateTime.tuesday) {\n          dateuntilfriday.add(Duration(days: 3));\n          print("5 Executed");\n        } else if (dateuntilfriday.weekday == DateTime.wednesday) {\n          dateuntilfriday.add(Duration(days: 2));\n          print("6 Executed");\n        } else if (dateuntilfriday.weekday == DateTime.thursday) {\n          dateuntilfriday.add(Duration(days: 1));\n          print("7 Executed");\n        } else {\n          print(\n              "and Error Occurent while getting the date for the next or last friday");\n        }\n\n        print(dateuntilfriday);\n      }\n

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Answer 1

我认为这可以实现您所寻求的：

DateTime weekdayOf(DateTime time, int weekday) => time.add(Duration(days: weekday - time.weekday));
DateTime fridayOf(DateTime time) => weekdayOf(time, 5);
DateTime saturdayOf(DateTime time) => weekdayOf(time, 6);
DateTime firstMonthDayOf(DateTime time) => DateTime(time.year, time.month, 1);
DateTime lastMonthDayOf(DateTime time) => DateTime(time.year, time.month + 1, 0);

我在这个月的最后一天使用了一个技巧。[0]下个月的一天是这个月的最后一天。

完整源代码

import 'package:flutter/material.dart';
import 'package:intl/intl.dart';

void main() {
  runApp(
    MaterialApp(
      debugShowCheckedModeBanner: false,
      title: 'Flutter Demo',
      home: HomePage(),
    ),
  );
}

class HomePage extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    final now = DateTime.now();
    final df = DateFormat.yMMMMEEEEd();
    return Scaffold(
      body: Column(
        crossAxisAlignment: CrossAxisAlignment.start,
        children: [
          Text('Today is ${df.format(now)}'),
          const SizedBox(height: 16.0),
          Text('Friday is ${df.format(fridayOf(now))}'),
          const SizedBox(height: 16.0),
          Text('Saturday is ${df.format(saturdayOf(now))}'),
          const SizedBox(height: 16.0),
          Text('First day of month is ${df.format(firstMonthDayOf(now))}'),
          const SizedBox(height: 16.0),
          Text('Last day of month is ${df.format(lastMonthDayOf(now))}'),
        ],
      ),
    );
  }
}

DateTime weekdayOf(DateTime time, int weekday) => time.add(Duration(days: weekday - time.weekday));
DateTime fridayOf(DateTime time) => weekdayOf(time, 5);
DateTime saturdayOf(DateTime time) => weekdayOf(time, 6);
DateTime firstMonthDayOf(DateTime time) => DateTime(time.year, time.month, 1);
DateTime lastMonthDayOf(DateTime time) => DateTime(time.year, time.month + 1, 0);