Flutter - providing dynamic data to TableCalendar widget

main.dart

import 'dart:async';
import 'dart:math';

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

void main() => runApp(MyApp());

class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      title: 'TableCalendar Demo',
      theme: ThemeData(primarySwatch: Colors.indigo),
      home: HomeScreen(),
    );
  }
}

class HomeScreen extends StatefulWidget {
  @override
  _HomeScreenState createState() => _HomeScreenState();
}

class _HomeScreenState extends State<HomeScreen> {
  CalendarController _calendarController;
  StreamController<Map<DateTime, List>> _streamController;

  @override
  void initState() {
    super.initState();
    _calendarController = CalendarController();
    _streamController = StreamController();
    _fetchEvents();
  }

  @override
  void dispose() {
    _calendarController.dispose();
    _streamController.close();
    super.dispose();
  }

  // Fetches two events on two random days within the current month
  void _fetchEvents() {
    final random = Random();
    final randomIntA = random.nextInt(13) + 1;
    final randomIntB = random.nextInt(13) + 14;

    final now = DateTime.now();
    final events = {
      DateTime(now.year, now.month, randomIntA): ['Random event #$randomIntA'],
      DateTime(now.year, now.month, randomIntB): ['Random event #$randomIntB'],
    };

    _streamController.add(events);
  }

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(title: Text('TableCalendar Dynamic Demo')),
      body: Center(
        child: Column(
          children: <Widget>[
            StreamBuilder<Map<DateTime, List>>(
              stream: _streamController.stream,
              builder: (context, snapshot) {
                if (!snapshot.hasData) {
                  return SizedBox(
                    height: 100.0,
                    width: 100.0,
                    child: Center(child: CircularProgressIndicator()),
                  );
                }

                final events = snapshot.data;

                return TableCalendar(
                  calendarController: _calendarController,
                  events: events,
                );
              },
            ),
            const SizedBox(height: 32.0),
            RaisedButton(
              onPressed: _fetchEvents,
              child: Text('Fetch events'),
            ),
          ],
        ),
      ),
    );
  }
}