Challenge 2 (BLoC)

main.dart

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

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

class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) => BlocProvider(
      create: (BuildContext context) => RootBloc(1),
      child: MaterialApp(
        home: Scaffold(body: MyWidget()),
      ));
}

class MyWidget extends StatelessWidget {
  @override
  Widget build(BuildContext context) => Stack(children: <Widget>[
        Center(
            child: BlocBuilder<RootBloc, RootState>(
                builder: (context, state) => Transform.scale(
                      scale: state.scale,
                      child: Container(
                        width: 100,
                        height: 100,
                        color: Colors.yellow,
                      ),
                    ))),
        Positioned(
            bottom: 0,
            left: 0,
            right: 0,
            child: BlocBuilder<RootBloc, RootState>(
              builder: (context, state) => Slider(
                value: state.scale,
                max: 2,
                onChanged: (newValue) =>
                    context.read<RootBloc>().add(MoveSlider(newValue)),
              ),
            ))
      ]);
}

//------------------------------Events------------------------------
abstract class RootEvents {}

class MoveSlider extends RootEvents {
  final double newValue;

  MoveSlider(this.newValue);
}
//------------------------------Events------------------------------

//------------------------------States------------------------------
class RootState {
  final double scale;

  RootState(this.scale);
}
//------------------------------States------------------------------

//-------------------------------Bloc-------------------------------
class RootBloc extends Bloc<RootEvents, RootState> {
  RootBloc(double initialValue) : super(RootState(initialValue)) {
    on<MoveSlider>((event, emit) => emit(RootState(event.newValue)));
  }
}
//-------------------------------Bloc-------------------------------