如何在flutter中设置周间隔日期，如2019年1月3日、2019年1月10日、2019年1月17日3个月？

dependencies:
  flutter:
    sdk: flutter
  intl: ^0.17.0

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

void main() {
  runApp(MyApp());
}

class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    List<DateTime> dates = getWeeklyDates(DateTime(2019, 1, 3), 3);

    return MaterialApp(
      home: Scaffold(
        appBar: AppBar(
          title: Text('Weekly Dates'),
        ),
        body: ListView.builder(
          itemCount: dates.length,
          itemBuilder: (context, index) {
            return ListTile(
              title: Text(DateFormat('yyyy年M月d日').format(dates[index])),
            );
          },
        ),
      ),
    );
  }

  List<DateTime> getWeeklyDates(DateTime startDate, int numberOfWeeks) {
    List<DateTime> dates = [];
    for (int i = 0; i < numberOfWeeks; i++) {
      DateTime date = startDate.add(Duration(days: i * 7));
      dates.add(date);
    }
    return dates;
  }
}