Edit 2022

如果有人感兴趣，我也为river pod移植(并重新制作)了这个包

https://pub.dev/packages/riverpod_messages/versions/1.0.0个

EDIT 2020-06-05

我开发了一种稍微好一点的方法来承受这种情况.

可以在This repo on github处找到它，这样您就可以在那里看到实现，或者使用这个包将其放入您的pubspec.yaml中

 provider_utilities:
    git:
      url: https://github.com/quantosapplications/flutter_provider_utilities.git

因此，当您需要向视图显示消息时，您可以:

1. 将您的ChangeNotifier扩展为MessageNotifierMixin，这给您的ChangeNotifier提供了两个属性error和info以及两个方法notifyError()和notifyInfo().

2. 使用MessageListener包装您的Scaffold，该MessageListener将在调用NotifyError()或NotifyInfo()时显示SnackBar

我给你举个例子:

ChangeNotifier个

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

class MyNotifier extends ChangeNotifier with MessageNotifierMixin {

  List<String> _properties = [];
  List<String> get properties => _properties;

  Future<void> load() async {

    try {
      /// Do some network calls or something else
      await Future.delayed(Duration(seconds: 1), (){

        _properties = ["Item 1", "Item 2", "Item 3"];
        notifyInfo('Successfully called load() method');

      });
    }
    catch(e) {
      notifyError('Error calling load() method');
    }

  }

}

View个

import 'package:flutter/material.dart';
import 'package:provider/provider.dart';
import 'package:provider_utilities/provider_utilities.dart';

import 'notifier.dart';

class View extends StatefulWidget {
  View({Key key}) : super(key: key);

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

class _ViewState extends State<View> {
  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(),
      body: MessageListener<MyNotifier>(
        child: Selector<MyNotifier, List<String>>(
          selector: (ctx, model) => model.properties,
          builder: (ctx, properties, child) => ListView.builder(
            itemCount: properties.length,
            itemBuilder: (ctx, index) => ListTile(
              title: Text(properties[index])
            ),
          ),
        )
      )
    );
  }
}

OLD ANSWER

非常感谢.

也许我找到了一个更简单的方法来处理这个问题，使用消费者强大的属性"child".

使用自定义的无状态小部件(我称之为ErrorListener，但它可以更改:)

class ErrorListener<T extends ErrorNotifierMixin> extends StatelessWidget {

  final Widget child;

  const ErrorListener({Key key, @required this.child}) : super(key: key);

  @override
  Widget build(BuildContext context) {
    return Consumer<T>(
      builder: (context, model, child){
        
        //here we listen for errors
        if (model.error != null) { 
          WidgetsBinding.instance.addPostFrameCallback((_){
             _handleError(context, model); });
        }

        // here we return child!
        return child;
      },
      child: child
    );
  }


  // this method will be called anytime an error occurs
  // it shows a snackbar but it could do anything you want
  void _handleError(BuildContext context, T model) {
    Scaffold.of(context)
    ..hideCurrentSnackBar()
    ..showSnackBar(
      SnackBar(
        backgroundColor: Colors.red[600],
        content: Row(
          mainAxisAlignment: MainAxisAlignment.spaceBetween,
          children: [
            Icon(Icons.error),
            Expanded(child: Padding( padding:EdgeInsets.only(left:16), child:Text(model.error) )),
          ],
        ),
      ),
    );

    // this will clear the error on model because it has been handled
    model.clearError();
  }
}

如果你想使用snackbar，这个小部件必须放在脚手架下.

我在这里使用mixin来确保模型有error属性和clarError()方法.

mixin ErrorNotifierMixin on ChangeNotifier {
  String _error;
  String get error => _error;

  void notifyError(dynamic error) {
    _error = error.toString();
    notifyListeners();
  }

  void clearError() {
    _error = null;
  }
}

举个例子，我们可以用这种方式

class _PageState extends State<Page> {

   // ...

@override 
  Widget build(BuildContext context) =>
    ChangeNotifierProvider(
      builder: (context) => MyModel(),
      child: Scaffold(
        body: ErrorListener<MyModel>(
          child: MyBody()
        )
      )
    );

}