我遇到了这个问题，我的应用程序没有构建，因为它显示
fatal error: 'Flutter/Flutter.h'
file not found
#import <Flutter/Flutter.h>
我已经为这个问题工作了一整天，但没有取得任何进展。这是一个简单的程序(打开flutter新项目时获得的初始代码(，并添加了firebase_core。
整个XCode输出：
Xcode's output:
↳
In file included from
/Users/alfieanil/Developer/flutter/.pub-cache/hosted/pub.dartlang.org/firebase_cor
e-1.10.0/ios/Classes/FLTFirebaseCorePlugin.m:5:
/Users/alfieanil/Developer/flutter/.pub-cache/hosted/pub.dartlang.org/firebase_cor
e-1.10.0/ios/Classes/FLTFirebaseCorePlugin.h:9:9: fatal error: 'Flutter/Flutter.h'
file not found
#import <Flutter/Flutter.h>
^~~~~~~~~~~~~~~~~~~
1 error generated.
note: Using new build system
note: Building targets in parallel
note: Planning build
note: Constructing build description
直到一两个月前，我的Flutter一直工作得很好。Flutter版本=2.0.6
非常感谢您的帮助。
感谢
我通过以下步骤修复了它：
1. Open your terminal in root level of your project.
2. run flutter upgrade.
3. Change SDK version in pubspec.yaml file
4. In my pubspec.yaml I just changed This line sdk: “>=2.7.0 <3.0.0” and replaced with sdk: “>=2.12.0 <3.0.0”
5. flutter clean
6. flutter run.
原始链接：https://fluttercorner.com/error-null-safety-features-are-disabled-for-this-library/(解决方案1(