bloc-example-for-daniel_oniya.dart

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

final Color darkBlue = Color.fromARGB(255, 18, 32, 47);

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

class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      theme: ThemeData.dark().copyWith(scaffoldBackgroundColor: darkBlue),
      debugShowCheckedModeBanner: false,
      home: Scaffold(
        body: Center(
          child: MyWidget(),
        ),
      ),
    );
  }
}

class MyWidget extends StatelessWidget {
  final Bloc bloc = Bloc();
  @override
  Widget build(BuildContext context) {
    // trigger event
    bloc.getUser();

    return StreamBuilder<UserModel>(
      stream: bloc.stream,
      builder: (context, snapshot) {
        // show loader while stream is null
        if (snapshot?.data == null) return CircularProgressIndicator();
        // build ui after completion
        // you may implement some stuff to check for errors
        return Text('Hello ${snapshot.data?.username ?? "User"}');
      },
    );
  }
}

class Bloc {
  StreamController<UserModel> _controller = StreamController<UserModel>();
  Stream<UserModel> get stream => _controller.stream;
  Sink<UserModel> get sink => _controller.sink;

  getUser() {
    // The delay is to fake a (network) request
    Future.delayed(Duration(seconds: 2), () {
      sink.add(UserModel(username: 'Oniya Daniel'));
    });
  }

  void dispose() => _controller.close();
}

class UserModel {
  String username;
  UserModel({this.username});
}