Runningflutter build web会给出以下错误：
flutter build web
Changing current working directory to: /home/forest/projects/icell/i_cell_parking_manager
Building without sound null safety
For more information see https://dart.dev/null-safety/unsound-null-safety
Target dart2js failed: Exception: ../../../snap/flutter/common/flutter/.pub-cache/hosted/pub.dartlang.org/cloud_firestore_web-1.0.1/lib/src/interop/utils/utils.dart:15:41:
Error: The argument type 'Object? Function(Object)' can't be assigned to the parameter type 'Object? Function(Object?)?' because 'Object?' is nullable and 'Object' isn't.
- 'Object' is from 'dart:core'.
return core_interop.dartify(jsObject, (Object object) {
^
../../../snap/flutter/common/flutter/.pub-cache/hosted/pub.dartlang.org/cloud_firestore_web-1.0.1/lib/src/interop/utils/utils.dart:39:41:
Error: The argument type 'dynamic Function(Object)' can't be assigned to the parameter type 'Object? Function(Object?)?' because 'Object?' is nullable and 'Object' isn't.
- 'Object' is from 'dart:core'.
return core_interop.jsify(dartObject, (Object object) {
^
Error: Compilation failed.
Compiling lib/main.dart for the Web... 8.3s
Exception: Failed to compile application for the Web.
为安卓构建没有任何错误(flutter build apk)。
flutter doctor
Flutter 2.0.3 • channel stable • https://github.com/flutter/flutter.git
Framework • revision 4d7946a68d (10 days ago) • 2021-03-18 17:24:33 -0700
Engine • revision 3459eb2436
Tools • Dart 2.12.2
Running flutter doctor...
Doctor summary (to see all details, run flutter doctor -v):
[✓] Flutter (Channel stable, 2.0.3, on Linux, locale en_US.UTF-8)
[✓] Android toolchain - develop for Android devices (Android SDK version 30.0.2)
[✓] Chrome - develop for the web
[!] Android Studio (not installed)
[✓] IntelliJ IDEA Ultimate Edition (version 2020.2)
[✓] Connected device (2 available)
! Doctor found issues in 1 category.
(未安装的 Androd 工作室很奇怪，因为我正在从它运行项目，而且我使用 AVD 的虚拟设备没有问题......
我的index.html导入了最新的库：
...
<script src="https://www.gstatic.com/firebasejs/7.8.0/firebase-auth.js"></script>
<script src="https://www.gstatic.com/firebasejs/7.20.0/firebase-app.js"></script>
相关pubspec.yaml部分：
dependencies:
flutter:
sdk: flutter
flutter_localizations:
sdk: flutter
flutter_spinkit: "^4.1.2"
cloud_firestore: ^1.0.1
cloud_functions: "^1.0.2"
provider: ^5.0.0
google_sign_in: ^5.0.0
firebase_core: ^1.0.1
firebase_messaging: ^9.0.0
firebase_auth: ^1.0.1
要在没有空安全的情况下进行发布版本，请使用：
flutter build web --no-sound-null-safety
生成的文件将放在build/web下。
注意：
--no-sound-null-safety必须作为标志传递给web子命令，而不是传递给build或flutter。
注意2：因此，构建集
<base href="/">，除非您从 Web 服务器根目录提供应用程序，否则您需要将值调整为正确的路径。存在一个 github 问题，需要通过命令行参数使base href可配置。当前文档建议手动设置基本 href。更新：相应的拉取请求现在合并到主分支。
解决方案是运行
flutter pub upgrade和flutter pub outdated然后flutter pub get，它解决了问题。
我怀疑有些东西被缓存了，并且在开始时并没有在 web 构建中使用所有新的依赖项，但不知道为什么它突然起作用了：\
如果您使用的是 Mac 或 Linux，请输入您的终端，以导出此EXTRA_FRONT_END_OPTIONS变量，如下所示
导出EXTRA_FRONT_END_OPTIONS=--无声音-零-安全