triple_widget.dart

...

  Widget build(BuildContext context){
    return Scaffold(
      body: Center(
        child: ScopedBuilder(
            store: counter,
            onState: (context, state) => Text('$state'),
            onError: (context, error) => Text(error.toString()),
            onLoading: (context) => CircularProgressIndicator(),
        );
      ),
    );
  }
...