我尝试通过执行以下步骤在现有的 flutter 应用程序中构建网络
1. flutter channel beta
2. flutter config --enable-web
3. flutter create .
4. flutter run -d chrome
来自https://flutter.dev/docs/get-started/web
但我不知道我在哪里犯了错误，或者这是 futter web 构建的问题，它一直失败。运行这些命令会显示此屏幕。
这是堆栈跟踪
══╡ EXCEPTION CAUGHT BY WIDGETS LIBRARY ╞═══════════════════════════════════════════════════════════
The following UnsupportedError was thrown building Builder:
Unsupported operation: Platform._operatingSystem
The relevant error-causing widget was:
MaterialApp org-dartlang-app:///packages/qpal/main.dart:13:12
When the exception was thrown, this was the stack:
package:dart-sdk/lib/_internal/js_dev_runtime/private/ddc_runtime/errors.dart 196:49 throw_
package:dart-sdk/lib/_internal/js_dev_runtime/patch/io_patch.dart 241:5 _operatingSystem
package:dart-sdk/lib/io/platform_impl.dart 62:40 get operatingSystem
package:dart-sdk/lib/io/platform.dart 73:45 get _operatingSystem
package:dart-sdk/lib/_internal/js_dev_runtime/private/ddc_runtime/utils.dart 77:6 get
package:dart-sdk/lib/io/platform.dart 97:40 get operatingSystem
package:platform/src/interface/local_platform.dart 21:45 get operatingSystem
package:platform/src/interface/platform.dart 41:38 get isIOS
package:firebase_messaging/firebase_messaging.dart 83:20 requestNotificationPermissions
package:qpal/services/firebase_helper.dart 41:23 requestNotification
package:qpal/main.dart 57:20 initState
package:flutter/src/widgets/framework.dart 4355:58 [_firstBuild]
package:flutter/src/widgets/framework.dart 4201:5 mount
package:flutter/src/widgets/framework.dart 3194:13 inflateWidget
package:flutter/src/widgets/framework.dart 2988:12 updateChild
package:flutter/src/widgets/framework.dart 5445:14 mount
package:flutter/src/widgets/framework.dart 3194:13 inflateWidget
package:flutter/src/widgets/framework.dart 2988:12 updateChild
package:flutter/src/widgets/framework.dart 4243:16 performRebuild
package:flutter/src/widgets/framework.dart 3947:5 rebuild
package:flutter/src/widgets/framework.dart 4206:5 [_firstBuild]
package:flutter/src/widgets/framework.dart 4201:5 mount
package:flutter/src/widgets/framework.dart 3194:13 inflateWidget
package:flutter/src/widgets/framework.dart 4201:5 mount
package:flutter/src/widgets/framework.dart 3194:13 inflateWidget
package:flutter/src/widgets/framework.dart 5551:32 mount
package:flutter/src/widgets/framework.dart 3194:13 inflateWidget
package:flutter/src/widgets/framework.dart 2988:12 updateChild
package:flutter/src/widgets/overlay.dart 591:16 mount
package:flutter/src/widgets/framework.dart 3194:13 inflateWidget
package:flutter/src/widgets/framework.dart 2988:12 updateChild
package:flutter/src/widgets/framework.dart 4243:16 performRebuild
package:flutter/src/widgets/framework.dart 3947:5 rebuild
package:flutter/src/widgets/framework.dart 4206:5 [_firstBuild]
package:flutter/src/widgets/framework.dart 4381:11 [_firstBuild]
package:flutter/src/widgets/framework.dart 4201:5 mount
package:flutter/src/widgets/framework.dart 3194:13 inflateWidget
package:flutter/src/widgets/framework.dart 2988:12 updateChild
package:flutter/src/widgets/framework.dart 4243:16 performRebuild
from splash
package:flutter/src/widgets/framework.dart 3947:5 rebuild
package:flutter/src/widgets/framework.dart 4206:5 [_firstBuild]
package:flutter/src/widgets/framework.dart 4201:5 mount
package:flutter/src/widgets/framework.dart 3194:13 inflateWidget
package:flutter/src/widgets/framework.dart 2988:12 updateChild
package:flutter/src/widgets/framework.dart 5445:14 mount
package:flutter/src/widgets/framework.dart 3194:13 inflateWidget
package:flutter/src/widgets/framework.dart 2988:12 updateChild
package:flutter/src/widgets/framework.dart 4243:16 performRebuild
package:flutter/src/widgets/framework.dart 3947:5 rebuild
package:flutter/src/widgets/framework.dart 4206:5 [_firstBuild]
package:flutter/src/widgets/framework.dart 4381:11 [_firstBuild]
package:flutter/src/widgets/framework.dart 4201:5 mount
package:flutter/src/widgets/framework.dart 3194:13 inflateWidget
package:flutter/src/widgets/framework.dart 2988:12 updateChild
package:flutter/src/widgets/framework.dart 5445:14 mount
package:flutter/src/widgets/framework.dart 3194:13 inflateWidget
package:flutter/src/widgets/binding.dart 999:5 mount
package:flutter/src/widgets/binding.dart 942:16 <fn>
package:flutter/src/widgets/framework.dart 2412:19 buildScope
package:flutter/src/widgets/binding.dart 941:12 attachToRenderTree
package:flutter/src/widgets/binding.dart 818:24 attachRootWidget
package:flutter/src/widgets/binding.dart 804:7 <fn>
package:dart-sdk/lib/_internal/js_dev_runtime/private/isolate_helper.dart 50:19 internalCallback
════════════════════════════════════════════════════════════════════════════════════════════════════
最佳答案
您可以尝试创建一个新项目并将额外的依赖项和 devDependency 复制到新的 pubspec.yml 中，复制整个 lib 文件夹并检查它是否正在运行。如果可以运行，则检查新项目和旧项目中您的sdk版本，并尝试使它们相同。
我遇到了类似的问题并尝试了上面的方法解决了我的问题。
environment:
sdk: ">=2.6.0 <3.0.0"
关于Flutter 在现有项目中构建 Web 不断失败，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/59593136/