未處理的異常：MissingPluginException（在通道 plugins.flutter.io/firebase_messaging 上找不到方法 getToken 的實現）

Question

我嘗試將 firebase 雲消息傳遞令牌發送到我的 flutter 應用程序。 哪個在 android 模擬器上運行 這里出了什么問題？。 我試過flutter run但這不起作用，我在這里使用了1.firebase_messaging: ^6.0.9 作為依賴項和2.

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

class Notifications_ extends StatefulWidget {
  @override
  _Notifications_State createState() => _Notifications_State();
}

class _Notifications_State extends State<Notifications_> {

  final FirebaseMessaging _messaging=FirebaseMessaging();

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

    _messaging.getToken().then((token)
    {
      print(token);
    });

  }

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: Text('notification'),
      ),
      body: Text('body testing'),
    );
  }
}

 E/flutter ( 5931): [ERROR:flutter/lib/ui/ui_dart_state.cc(157)] Unhandled Exception: MissingPluginException(No implementation found for method getToken on channel plugins.flutter.io/firebase_messaging)

E/flutter（5931）：#0 MethodChannel.invokeMethod（包：flutter/src/services/platform_channel.dart:319:7）E/flutter（5931）：E/flutter（5931）：#1 FirebaseMessaging.getToken（包:firebase_messaging/firebase_messaging.dart:150:27) E/flutter (5931): #2 _Notifications_State.initState (package:sampletestingpro/Notification.dart:17:16) E/flutter (5931): #3 StatefulElement._firstBuild (package :flutter/src/widgets/framework.dart:4355:58) E/flutter (5931): #4 ComponentElement.mount (package:flutter/src/widgets/framework.dart:4201:5) E/flutter (5931) : #5 Element.inflateWidget (package:flutter/src/widgets/framework.dart:3194:14) E/flutter (5931): #6 Element.updateChild (package:flutter/src/widgets/framework.dart:2988: 12) E/flutter (5931): #7 ComponentElement.performRebuild (package:flutter/src/widgets/framework.dart:4243:16) E/flutter (5931): #8 Element.rebuild (package:flutter/src/ widgets/framework.dart:3947:5) E/flutter (5931): #9 StatelessElement.update (package:flutter/src/widg ets/framework.dart:4298:5) E/flutter (5931): #10 Element.updateChild (package:flutter/src/widgets/framework.dart:2977:15) E/flutter (5931): #11 ComponentElement。 performRebuild (package:flutter/src/widgets/framework.dart:4243:16) E/flutter (5931): #12 Element.rebuild (package:flutter/src/widgets/framework.dart:3947:5) E/flutter (5931): #13 StatelessElement.update (package:flutter/src/widgets/framework.dart:4298:5) E/flutter (5931): #14 Element.updateChild (package:flutter/src/widgets/framework.dart :2977:15) E/flutter (5931): #15 ComponentElement.performRebuild (package:flutter/src/widgets/framework.dart:4243:16) E/flutter (5931): #16 Element.rebuild (package:flutter /src/widgets/framework.dart:3947:5) E/flutter (5931): #17 ProxyElement.update (package:flutter/src/widgets/framework.dart:4557:5) E/flutter (5931): # 18 Element.updateChild (package:flutter/src/widgets/framework.dart:2977:15) E/flutter (5931): #19 ComponentElement.performRebuild (package:flutter/src/widgets/framework .dart:4243:16) E/flutter (5931): #20 Element.rebuild (package:flutter/src/widgets/framework.dart:3947:5) E/flutter (5931): #21 ProxyElement.update (package :flutter/src/widgets/framework.dart:4557:5) E/flutter (5931): #22 Element.updateChild (package:flutter/src/widgets/framework.dart:2977:15) E/flutter (5931) : #23 RenderObjectElement.updateChildren (package:flutter/src/widgets/framework.dart:5161:32) E/flutter (5931): #24 MultiChildRenderObjectElement.update (package:flutter/src/widgets/framework.dart:5561: 17) E/flutter ( 5931): #25 Element.updateChild (package:flutter/src/widgets/framework.dart:2977:15) E/flutter (5931): #26 ComponentElement.performRebuild (package:flutter/src/ widgets/framework.dart:4243:16) E/flutter (5931): #27 Element.rebuild (package:flutter/src/widgets/framework.dart:3947:5) E/flutter (5931): #28 StatefulElement。更新 (package:flutter/src/widgets/framework.dart:4413:5) E/flutter (5931): #29 Element.updateChild (package:flutter/src/widgets/framework.dart :2977:15) E/flutter (5931): #30 ComponentElement.performRebuild (package:flutter/src/widgets/framework.dart:4243:16) E/flutter (5931): #31 Element.rebuild (package:flutter /src/widgets/framework.dart:3947:5) E/flutter (5931): #32 ProxyElement.update (package:flutter/src/widgets/framework.dart:4557:5) E/flutter (5931): # 33 Element.updateChild (package:flutter/src/widgets/framework.dart:2977:15) E/flutter (5931): #34 ComponentElement.performRebuild (package:flutter/src/widgets/framework.dart:4243:16) E/flutter (5931): #35 Element.rebuild (package:flutter/src/widgets/framework.dart:3947:5) E/flutter (5931): #36 StatefulElement.update (package:flutter/src/widgets/ framework.dart:4413:5) E/flutter (5931): #37 Element.updateChild (package:flutter/src/widgets/framework.dart:2977:15) E/flutter (5931): #38 SingleChildRenderObjectElement.update ( package:flutter/src/widgets/framework.dart:5452:14) E/flutter (5931): #39 Element.updateChild (package:flutter/src/widgets/framework.dart:2977:1 5) E/flutter (5931): #40 ComponentElement.performRebuild (package:flutter/src/widgets/framework.dart:4243:16) E/flutter (5931): #41 Element.rebuild (package:flutter/src/ widgets/framework.dart:3947:5) E/flutter (5931): #42 StatelessElement.update (package:flutter/src/widgets/framework.dart:4298:5) E/flutter (5931): #43 元素。 updateChild (package:flutter/src/widgets/framework.dart:2977:15) E/flutter (5931): #44 SingleChildRenderObjectElement.update (package:flutter/src/widgets/framework.dart:5452:14) E/flutter （5931）：#45 Element.update。

Answer 1

將 google JSON 服務文件保存在 app 文件夾中，我錯誤地將 JSON 文件放在 src/ 文件夾中，這就是為什么我收到錯誤的原因

Answer 2

因此，在嘗試了許多解決方案后，這對我有用！

MissingPluginException（在頻道 plugins.flutter.io/firebase_messaging_background 上找不到方法 FcmDartService#initialized 的實現