错误 "FormatException: Unexpected character (at character 1)" 即使在默认的默认 flutter web 项目中

Question

每当我创建一个新的 flutter web 项目时，它都会给我同样的错误：Unexpected Character (at character 1).

当我运行 webdev serve 时，它给出一个空白屏幕并停止。并且，在 webdev 守护程序上我得到了错误。

代码我没有做任何改动，原样执行，即默认的flutter web项目

我已经卸载并重新安装，尝试了 flutter clean，但是 none 可以正常工作：

详情如下：

Unhandled exception:
FormatException: Unexpected character (at character 1)
Not Found
^

#0      _ChunkedJsonParser.fail (dart:convert-patch/convert_patch.dart:1392:5)
#1      _ChunkedJsonParser.parseNumber (dart:convert-patch/convert_patch.dart:1259:9)
#2      _ChunkedJsonParser.parse (dart:convert-patch/convert_patch.dart:924:22)
#3      _parseJson (dart:convert-patch/convert_patch.dart:29:10)
#4      JsonDecoder.convert (dart:convert/json.dart:493:36)
#5      JsonCodec.decode (dart:convert/json.dart:151:41)
#6      jsonDecode (dart:convert/json.dart:94:10)
#7      parse (package:source_maps/parser.dart:27:15)
#8      Sources.scriptParsed (package:dwds/src/debugging/sources.dart:62:19)
<asynchronous suspension>
#9      _RootZone.runUnaryGuarded (dart:async/zone.dart:1314:10)
#10     CastStreamSubscription._onData (dart:_internal/async_cast.dart:81:11)
#11     _RootZone.runUnaryGuarded (dart:async/zone.dart:1314:10)
#12     _BufferingStreamSubscription._sendData (dart:async/stream_impl.dart:336:11)
#13     _BufferingStreamSubscription._add (dart:async/stream_impl.dart:263:7)
#14     _SinkTransformerStreamSubscription._add (dart:async/stream_transformers.dart:68:11)
#15     _EventSinkWrapper.add (dart:async/stream_transformers.dart:15:11)
#16     WipDomain.eventStream.<anonymous closure>.<anonymous closure> (package:webkit_inspection_protocol/webkit_inspection_protocol.dart:301:26)
#17     _HandlerEventSink.add (dart:async/stream_transformers.dart:228:7)
#18     _SinkTransformerStreamSubscription._handleData (dart:async/stream_transformers.dart:120:24)
#19     _RootZone.runUnaryGuarded (dart:async/zone.dart:1314:10)
#20     _BufferingStreamSubscription._sendData (dart:async/stream_impl.dart:336:11)
#21     _DelayedData.perform (dart:async/stream_impl.dart:591:14)
#22     _StreamImplEvents.handleNext (dart:async/stream_impl.dart:707:11)
#23     _PendingEvents.schedule.<anonymous closure> (dart:async/stream_impl.dart:667:7)
#24     _microtaskLoop (dart:async/schedule_microtask.dart:41:21)
#25     _startMicrotaskLoop (dart:async/schedule_microtask.dart:50:5)
#26     _runPendingImmediateCallback (dart:isolate-patch/isolate_patch.dart:116:13)
#27     _RawReceivePortImpl._handleMessage (dart:isolate-patch/isolate_patch.dart:173:5)
pub failed (255)

我的main.dart

import 'package:flutter_web/material.dart';

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

class MyApp extends StatelessWidget {
  // This widget is the root of your application.
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      title: 'Flutter Demo',
      theme: ThemeData(
        primarySwatch: Colors.blue,
      ),
      home: MyHomePage(title: 'Flutter Demo Home Page'),
    );
  }
}

class MyHomePage extends StatelessWidget {
  MyHomePage({Key key, this.title}) : super(key: key);

  final String title;

  @override
  Widget build(BuildContext context) {
    // The Flutter framework has been optimized to make rerunning build methods
    // fast, so that you can just rebuild anything that needs updating rather
    // than having to individually change instances of widgets.
    return Scaffold(
      appBar: AppBar(
        title: Text(title),
      ),
      body: Center(
        // Center is a layout widget. It takes a single child and positions it
        // in the middle of the parent.
        child: Column(
          // Column is also layout widget. It takes a list of children and
          // arranges them vertically. By default, it sizes itself to fit its
          // children horizontally, and tries to be as tall as its parent.
          //
          // Invoke "debug painting" (choose the "Toggle Debug Paint" action
          // from the Flutter Inspector in Android Studio, or the "Toggle Debug
          // Paint" command in Visual Studio Code) to see the wireframe for each
          // widget.
          //
          // Column has various properties to control how it sizes itself and
          // how it positions its children. Here we use mainAxisAlignment to
          // center the children vertically; the main axis here is the vertical
          // axis because Columns are vertical (the cross axis would be
          // horizontal).
          mainAxisAlignment: MainAxisAlignment.center,
          children: <Widget>[
            Text(
              'Hello, World!',
            ),
          ],
        ),
      ), // This trailing comma makes auto-formatting nicer for build methods.
    );
  }
}

https://github.com/ipshitag/hello_world/tree/master/helloworld

Answer 1

这是 Windows 上的一个 webdev 错误，已在 webdev v2.5.0 中修复：

运行 pub global activate webdev 更新到最新版本。

错误 "FormatException: Unexpected character (at character 1)" 即使在默认的默认 flutter web 项目中

Error "FormatException: Unexpected character (at character 1)" even in default default flutter web project

dart

visual-studio-code

flutter

flutter-web