Example streamBuilder + hot reload

main.dart

import 'dart:async';

import 'package:flutter/material.dart';

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

class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      title: 'Flutter Demo',
      theme: ThemeData(
        primarySwatch: Colors.blue,
      ),
      home: MyHomePage(presenter: Presenter()),
    );
  }
}

class MyHomePage extends StatefulWidget {
  final Presenter presenter;

  MyHomePage({Key key, this.presenter}) : super(key: key);

  @override
  _MyHomePageState createState() => _MyHomePageState();
}

class _MyHomePageState extends State<MyHomePage> {
  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: Text("Test stream builder"),
      ),
      body: Center(
        child: StreamBuilder<Object>(
          stream: widget.presenter.stream,
          builder: (context, snapshot) {
            if (!snapshot.hasData ) return CircularProgressIndicator();

            print("snaphot.hasData: ${snapshot.hasData}");
            print("lastVal: ${widget.presenter.lastVal}");

            return Column(
              mainAxisAlignment: MainAxisAlignment.center,
              children: widget.presenter.lastVal.map((int i) => Text(i.toString())).toList()
            );
          }
        ),
      ),
    );
  }
}

class Presenter {
  StreamController<List<int>> _controller = StreamController<List<int>>.broadcast();
  Stream get stream => _controller.stream;
  
  List<int> _lastVal;
  List<int> get lastVal => _lastVal;

  Presenter(){
    _getData();
  }

  Future<void> _getData() async {
    await Future.delayed(Duration(seconds: 2));

    List<int> testList = [1,2,3];
    _lastVal = testList;

    _controller.add(testList);
  }
}