main.dart

import "dart:async";
import 'package:flutter/material.dart';

final Color darkBlue = Color.fromARGB(255, 18, 32, 47);

void main() {
  runApp(MyApp());
}

class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    final _pressed = StreamController<Map<String, dynamic>>();
    final pressed = _pressed.stream.asBroadcastStream();

    void onSelect(int id, bool isSelected) =>
        _pressed.add({'id': id, 'isSelected': isSelected});

    return MaterialApp(
      theme: ThemeData.dark().copyWith(scaffoldBackgroundColor: darkBlue),
      debugShowCheckedModeBanner: false,
      home: Scaffold(
        body: Center(
            child: Column(
          children: <Widget>[
            Row(
              children: <Widget>[
                MySelectButton(0, onSelect, pressed),
                MySelectButton(1, onSelect, pressed),
              ],
            ),
            Row(
              children: <Widget>[
                MySelectButton(2, onSelect, pressed),
                MySelectButton(3, onSelect, pressed),
              ],
            ),
          ],
        )),
      ),
    );
  }
}

class MySelectButton extends StatefulWidget {
  final Function onPressed;

  Stream<Map<String, dynamic>> select;

  final int id;

  MySelectButton(this.id, this.onPressed, this.select);

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

class _MySelectButtonState extends State<MySelectButton> {
  StreamController<bool> _isSelected = StreamController();
  Stream<bool> isSelected;

  @override
  void initState() {
    super.initState();

    _isSelected = StreamController();
    isSelected = _isSelected.stream;

    widget.select.listen((id) {

      if (id['id'] == widget.id) {
        _isSelected.add(id['isSelected']);
      } else {
        _isSelected.add(false);
      }

    });
  }

  @override
  void dispose() {
    _isSelected.close();
    super.dispose();
  }

  bool selected = false;

  @override
  Widget build(BuildContext context) {
    return StreamBuilder<bool>(
        key: Key('button_${widget.id}'),
        stream: isSelected,
        initialData: selected,
        builder: (context, snapshot) {
          return Padding(
            key: Key('button_${widget.id}'),
            padding: EdgeInsets.all(10.0),
            child: GestureDetector(
                onTap: () {
                  selected = !selected;
                  widget.onPressed(widget.id, selected);
                },
                child: Container(
                  width: 300.0,
                  height: 100.0,
                  color: snapshot.data ? Colors.redAccent : Colors.blueAccent,
                )),
          );
        });
  }
}