stream.dart

StreamController<String> _accountController = new StreamController();

@override
void initState() {
  super.initState();
  Future<void>.delayed(
    Duration(seconds: 2),
    () => _accountController.add('Data Loaded'),
  );
}

Widget build(BuildContext context) {
  return Container(
    child: StreamBuilder<String>(
      stream: _accountController.stream,
      builder: (context, snapshot) {
        if (snapshot.hasError) {
          return Center(child: Text(snapshot.error.toString()));
        }
        if (snapshot.hasData) {
          return Center(child: Text(snapshot.data));
        }
        return CircularProgressIndicator();
      },
    ),
  );
}