Last Updated on 2021-10-15 by Clay
The code after the dart version upgrade needs to enable the so-called Null-Safety to compile. If the code disable Null-Safety, the following error will occur:
This requires the 'non-nullable' language feature to be enabled. Try updating your pubspec.yaml to set the minimum SDK constraint to 2.12.0 or higher, and running 'pub get'.Solution: Enable Null-Safety
1. Confirm your Dart version (in my example, it needs to be at least 2.12)
dart --version
If the version is too low, you need to upgrade to the minimum version required.
2. Use the following commands to confirm the package's requirement
dart pub upgrade --null-safety
dart pub get
dart pub outdated --mode=null-safety3. Migration
If there is an error, it means there is a library and the package does not support Null-Safety.
dart pub outdated --mode=null-safetyReferences
- https://stackoverflow.com/questions/64621051/how-to-enable-null-safety-in-flutter
- https://github.com/flutter/flutter/issues/62414
- https://dart.dev/null-safety/migration-guide
The current Dart SDK version is 3.1.0.
Because pizzaflutterapp depends on cupertino_icons >=0.1.1 <1.0.1 which doesn't support null safety, version solving failed.
The lower bound of "sdk: '=2.0.0-dev.28.0 <3.0.0'" must be 2.12.0 or higher to enable null safety.
For details, see https://dart.dev/null-safety
You can try the following suggestion to make the pubspec resolve:
* Try upgrading your constraint on cupertino_icons: flutter pub add cupertino_icons:^1.0.6