“示例”类型不是“示例”类型的子类型

Question

我从这种语言开始，并尝试创建一个应用程序，该应用程序可以接收来自服务器的消息(通过websocket)并在ListView中显示它们。

我在一个专用文件中创建了一个类，用于将这些消息转换为实体。

但从跟踪来看，我在几个文件中使用的类类型似乎并不是.“同样的”。

跟踪：

E/flutter ( 9655): [ERROR:flutter/lib/ui/ui_dart_state.cc(157)] Unhandled Exception: type 'Example' is not a subtype of type 'Example' of 'example' where
E/flutter ( 9655):   Example is from package:exampleProject/components/Example.dart
E/flutter ( 9655):   Example is from package:exampleProject/components/example.dart
E/flutter ( 9655): 
E/flutter ( 9655): #0      Plugin._onMessageReceived.<anonymous closure> (package:exampleProject/plugin.dart:35:15)
E/flutter ( 9655): #1      Iterable.forEach (dart:core/iterable.dart:279:30)
E/flutter ( 9655): #2      Plugin._onMessageReceived (package:exampleProject/plugin.dart:31:16)
E/flutter ( 9655): #3      WebSocketsNotifications._onReceptionOfMessageFromServer.<anonymous closure> (package:exampleProject/websockets.dart:95:15)
E/flutter ( 9655): #4      Iterable.forEach (dart:core/iterable.dart:279:30)
E/flutter ( 9655): #5      WebSocketsNotifications._onReceptionOfMessageFromServer (package:exampleProject/websockets.dart:94:16)
E/flutter ( 9655): #6      _rootRunUnary (dart:async/zone.dart:1134:38)
E/flutter ( 9655): #7      _CustomZone.runUnary (dart:async/zone.dart:1031:19)
E/flutter ( 9655): #8      _CustomZone.runUnaryGuarded (dart:async/zone.dart:933:7)
E/flutter ( 9655): #9      _BufferingStreamSubscription._sendData (dart:async/stream_impl.dart:338:11)
E/flutter ( 9655): #10     _BufferingStreamSubscription._add (dart:async/stream_impl.dart:265:7)
E/flutter ( 9655): #11     _ForwardingStreamSubscription._add (dart:async/stream_pipe.dart:134:11)
E/flutter ( 9655): #12     _ForwardingStream._handleData (dart:async/stream_pipe.dart:100:10)
E/flutter ( 9655): #13     _ForwardingStreamSubscription._handleData (dart:async/stream_pipe.dart:166:13)
E/flutter ( 9655): #14     _rootRunUnary (dart:async/zone.dart:1134:38)
E/flutter ( 9655): #15     _CustomZone.runUnary (dart:async/zone.dart:1031:19)
E/flutter ( 9655): #16     _CustomZone.runUnaryGuarded (dart:async/zone.dart:933:7)
E/flutter ( 9655): #17     _BufferingStreamSubscription._sendData (dart:async/stream_impl.dart:338:11)
E/flutter ( 9655): #18     _BufferingStreamSubscription._add (dart:async/stream_impl.dart:265:7)
E/flutter ( 9655): #19     _SyncStreamControllerDispatch._sendData (dart:async/stream_controller.dart:766:19)
E/flutter ( 9655): #20     _StreamController._add (dart:async/stream_controller.dart:642:7)
E/flutter ( 9655): #21     _rootRunUnary (dart:async/zone.dart:1134:38)
E/flutter ( 9655): #22     _CustomZone.runUnary (dart:async/zone.dart:1031:19)
E/flutter ( 9655): #23     _CustomZone.runUnaryGuarded (dart:async/zone.dart:933:7)
E/flutter ( 9655): #24     _BufferingStreamSubscription._sendData (dart:async/stream_impl.dart:338:11)
E/flutter ( 9655): #25     _BufferingStreamSubscription._add (dart:async/stream_impl.dart:265:7)
E/flutter ( 9655): #26     _SyncStreamControllerDispatch._sendData (dart:async/stream_controller.dart:766:19)
E/flutter ( 9655): #27     _StreamController._add (dart:async/stream_controller.dart:642:7)
E/flutter ( 9655): #28     _StreamController.add (dart:async/stream_controller.dart:588:5)
E/flutter ( 9655): #29     new _WebSocketImpl._fromSocket.<anonymous closure> (dart:_http/websocket_impl.dart:1143:21)
E/flutter ( 9655): #30     _rootRunUnary (dart:async/zone.dart:1134:38)
E/flutter ( 9655): #31     _CustomZone.runUnary (dart:async/zone.dart:1031:19)
E/flutter ( 9655): #32     _CustomZone.runUnaryGuarded (dart:async/zone.dart:933:7)
E/flutter ( 9655): #33     _BufferingStreamSubscription._sendData (dart:async/stream_impl.dart:338:11)
E/flutter ( 9655): #34     _BufferingStreamSubscription._add (dart:async/stream_impl.dart:265:7)
E/flutter ( 9655): #35     _SinkTransformerStreamSubscription._add (dart:async/stream_transformers.dart:70:11)
E/flutter ( 9655): #36     _EventSinkWrapper.add (dart:async/stream_transformers.dart:17:11)
E/flutter ( 9655): #37     _WebSocketProtocolTransformer._messageFrameEnd (dart:_http/websocket_impl.dart:336:22)
E/flutter ( 9655): #38     _WebSocketProtocolTransformer.add (dart:_http/websocket_impl.dart:231:46)
E/flutter ( 9655): #39     _SinkTransformerStreamSubscription._handleData (dart:async/stream_transformers.dart:122:24)
E/flutter ( 9655): #40     _rootRunUnary (dart:async/zone.dart:1134:38)
E/flutter ( 9655): #41     _CustomZone.runUnary (dart:async/zone.dart:1031:19)
E/flutter ( 9655): #42     _CustomZone.runUnaryGuarded (dart:async/zone.dart:933:7)
E/flutter ( 9655): #43     _BufferingStreamSubscription._sendData (dart:async/stream_impl.dart:338:11)
E/flutter ( 9655): #44     _BufferingStreamSubscription._add (dart:async/stream_impl.dart:265:7)
E/flutter ( 9655): #45     _SyncStreamControllerDispatch._sendData (dart:async/stream_controller.dart:766:19)
E/flutter ( 9655): #46     _StreamController._add (dart:async/stream_controller.dart:642:7)
E/flutter ( 9655): #47     _StreamController.add (dart:async/stream_controller.dart:588:5)
E/flutter ( 9655): #48     _Socket._onData (dart:io-patch/socket_patch.dart:1831:41)
E/flutter ( 9655): #49     _rootRunUnary (dart:async/zone.dart:1138:13)
E/flutter ( 9655): #50     _CustomZone.runUn

这里是我的实体类：

// example.dart

class Example {
  String name;

  Example.fromJson(Map<String, dynamic> decodedJson) {
    name = decodedJson['name'];
  }
}

这里是一个插件，它与套接字管理器通信，接收来自它的消息，并将内容转换为一个实体：

// plugin.dart

import 'dart:convert';

import 'package:flutter/foundation.dart';
import 'package:exampleProject/websockets.dart';
import 'package:exampleProject/components/Example.dart';

Plugin plugin = new Plugin();

class Plugin {
  static final Plugin _plugin = new Plugin._internal();

  factory Plugin() => _plugin;

  Plugin._internal() {
    // Initialize sockets
    sockets.initCommunication();

    sockets.addListener(_onMessageReceived);
  }

  _onMessageReceived(message) {
    Map<String, dynamic> decodedJson = json.decode(message);

    _listeners.forEach((Function callback) {

      // --------------------------------------------------------------< Creating the class instance
      Example example = Example.fromJson(decodedJson);
      // --------------------------------------------------------------< Send it to listeners
      callback(example);
    });
  }

  ObserverList<Function> _listeners = new ObserverList<Function>();

  addListener(Function callback) {
    _listeners.add(callback);
  }

  removeListener(Function callback) {
    _listeners.remove(callback);
  }
}

main：

// main.dart

import 'package:flutter/material.dart';

import 'package:exampleProject/websockets.dart';
import 'package:exampleProject/plugin.dart';
import 'package:exampleProject/components/Example.dart';

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

class App extends StatefulWidget {
  @override
  _AppState createState() => _AppState();
}

class _AppState extends State<App> {
  // --------------------------------------------------------------< List
  List<Example> examples = [];

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

    plugin.addListener(_onMessageReceived);
  }

  @override
  void dispose() {
    plugin.removeListener(_onMessageReceived);
    super.dispose();
  }

  // --------------------------------------------------------------< List insert
  _onMessageReceived(Example example) {
    examples.insert(0, example);
    // Force render
    setState(() {});
  }

  [...]
}

我错过了什么？

预先谢谢的帮助

Answer 1

这一行：

import 'package:exampleProject/components/Example.dart';

应：

import 'package:exampleProject/components/example.dart';

因为这就是它的名字。类名是Example，但文件名不是。