我正在尝试在 flutter(using dart) 中构建一个文本语音应用程序。运行时出现此错误，但据我所知，代码没有问题。我已经粘贴了下面的完整代码。

我遇到的错误是在调用 onListen 处理程序时。它指出语音转文本包中的错误，甚至不是我的代码。请看下面的图片和错误。

TypeError: result[$item] is not a function
    at speech_to_text_web.SpeechToTextPlugin.new.[_onResult] (http://localhost:53227/packages/speech_to_text/speech_to_text_web.dart.lib.js:143:36)
    at http://localhost:53227/packages/speech_to_text/speech_to_text_web.dart.lib.js:97:98
    at Object._checkAndCall (http://localhost:53227/dart_sdk.js:5242:16)
    at Object.dcall (http://localhost:53227/dart_sdk.js:5247:17)
    at SpeechRecognition.<anonymous> (http://localhost:53227/dart_sdk.js:100617:100)

import 'package:flutter/material.dart';
import 'package:speech_to_text/speech_to_text.dart' as stt;
import 'package:avatar_glow/avatar_glow.dart';

void main() {
  runApp(MyApp());
}

class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      title: 'Flutter voice',debugShowCheckedmodeBanner: false,theme: ThemeData(
        primarySwatch: Colors.red,visualDensity: VisualDensity.adaptivePlatformDensity,),home: SpeechScreen(),);
  }
}

class SpeechScreen extends StatefulWidget {
  @override
  _SpeechScreenState createState() => _SpeechScreenState();
}

class _SpeechScreenState extends State<SpeechScreen> {
  stt.SpeechToText _speech = stt.SpeechToText();
  bool _isListening = false;
  String _text = 'Press the button and start speaking';
  double _confidence = 1.0;



  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: Text('Confidence: ${(_confidence * 100.0).toStringAsFixed(1)}%'),floatingactionButtonLocation: FloatingactionButtonLocation.centerFloat,floatingactionButton: AvatarGlow(
        animate: _isListening,glowColor: Theme.of(context).primaryColor,endRadius: 75.0,duration: const Duration(milliseconds: 2000),repeatPauseDuration: const Duration(milliseconds: 100),repeat: true,child: FloatingactionButton(
          onpressed: _listen,child: Icon(_isListening ? Icons.mic : Icons.mic_none),body: SingleChildScrollView(
        reverse: true,child: Container(
          padding: const EdgeInsets.fromLTRB(30.0,30.0,150.0),child: Text(
            _text,style: const TextStyle(
              fontSize: 32.0,color: Colors.black,fontWeight: FontWeight.w400,);
  }

  void _listen() async {
    if (!_isListening) {
      bool available = await _speech.initialize(
        onStatus: (val) => print('onStatus: $val'),onError: (val) => print('onError: $val'),);
      if (available) {
        setState(() => _isListening = true);
        _speech.listen(
            onResult: (val) => setState(() {
              _text = val.recognizedWords;
              if (val.hasConfidenceRating && val.confidence > 0) {
                _confidence = val.confidence;
              }
            }));
      }
    } else {
      setState(() => _isListening = false);
      _speech.stop();
    }
  }
}

错误