main.dart

import 'dart:async';

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

void main() {
  final controller = new StreamController(sync: true);
  controller.add(2);
  new Future.delayed(const Duration(seconds: 1)).then((_) {
    controller.add(3);
  });
  runApp(new MaterialApp(home: new StreamBuilder(
    stream: controller.stream,
    builder: (context, snapshot) {
      if (snapshot.hasData) {
        return new Text('${snapshot.data}', textDirection: TextDirection.ltr,);
      }
      // this is never displayed
      return new Text('LOADING', textDirection: TextDirection.ltr,);
    })));
}