Build widgets in response to notifications (Flutter)

notification_builder.dart

import 'package:flutter/widgets.dart';

typedef NotificationBuilderCallback<T extends Notification> = Widget Function(
    BuildContext context, T? notification);

typedef NotificationCondition<T extends Notification> = bool Function(
    T notification);

class NotificationConsumer<T extends Notification> extends StatefulWidget {
  final NotificationBuilderCallback<T> builder;
  final NotificationListenerCallback<T>? onNotification;
  final NotificationCondition? when;

  const NotificationConsumer({
    Key? key,
    required this.builder,
    this.onNotification,
    this.when,
  }) : super(key: key);

  @override
  _NotificationConsumerState createState() => _NotificationConsumerState<T>();
}

class _NotificationConsumerState<T extends Notification>
    extends State<NotificationConsumer<T>> {
  T? _notification;

  @override
  Widget build(BuildContext context) => NotificationListener(
        child: widget.builder(context, _notification),
        onNotification: _onNotification,
      );

  bool _onNotification(T notification) {
    if (widget.when?.call(notification) ?? true) {
      setState(() => _notification = notification);
      return widget.onNotification?.call(notification) == true;
    }
    return false;
  }
}