reactivity issue

notified_container.dart

import 'package:flutter/material.dart';

enum NotifiedContainerType {
  success,
  info,
  warning,
  error
}

class NotifiedContainer extends StatefulWidget {

  final bool noticeDisplayed;
  final NotifiedContainerType type;
  final String message;
  final Widget child;

  NotifiedContainer({
    this.noticeDisplayed = true,
    this.type = NotifiedContainerType.info,
    this.message = 'Empty message',
    this.child
  }) : super();

  @override
  State<StatefulWidget> createState() => _NotifiedContainerState(
    noticeDisplayed: noticeDisplayed,
    type: type,
    message: message,
    child: child
  );
}

class _NotifiedContainerState extends State<NotifiedContainer> {

  bool noticeDisplayed;
  NotifiedContainerType type;
  String message;
  Widget child;

  _NotifiedContainerState({
    this.noticeDisplayed,
    this.type,
    this.message,
    this.child
  }) : super();

  @override
  Widget build(BuildContext context) {

    if (!this.noticeDisplayed)
      return child;

    Color color;

    switch (type) {

      case NotifiedContainerType.success:
        color = Color(0xFF36C8A0);
        break;

      case NotifiedContainerType.info:
        color = Color(0xFFBBBBBB);
        break;

      case NotifiedContainerType.warning:
        color = Color(0xFFFFE900);
        break;

      case NotifiedContainerType.error:
        color = Color(0xFFF43551);
        break;

      default:
        throw 'Unknown value of NotifiedContainerType.';
    }

    Widget notification = Container(
      padding: EdgeInsets.fromLTRB(
        20.0,
        40.0,
        20.0,
        20.0
      ),
      width: double.infinity,
      color: color,
      child: Text(
        message,
        style: TextStyle(
          fontSize: 16.0,
          color: Color(0xFFFFFFFF)
        ),
      ),
    );

    return Stack(
      children: <Widget>[
        child,
        notification
      ],
    );
  }
}