我已经下载了 flutter_windows_2.0.5-stable.zip 并安装了 Flutter 2.0.5。
当我运行一个 v1.24.0 项目时，我得到以下输出：
Running "flutter pub get" in get_json ...
The current Dart SDK version is 2.12.0-29.10.beta.
Because flutter_easyloading 3.0.0 requires SDK version >=2.12.0 <3.0.0 and no versions of flutter_easyloading match >3.0.0 <4.0.0, flutter_easyloading ^3.0.0 is forbidden.
So, because get_json depends on flutter_easyloading ^3.0.0, version solving failed.
pub get failed (1; So, because get_json depends on flutter_easyloading ^3.0.0, version solving failed.)
pubspec.yaml 的内容：
dependencies:
flutter:
sdk: flutter
http: ^0.12.2
json_annotation: ^2.0.0 #^4.0.1
rflutter_alert: ^1.1.0 #^2.0.2
pdf_flutter: ^1.1.4
syncfusion_flutter_pdfviewer: ^18.4.49-beta
webview_flutter: ^1.0.7 #^2.0.4
flutter_easyloading: ^3.0.0
cupertino_icons: ^1.0.1
dev_dependencies:
flutter_test:
sdk: flutter
build_runner: ^1.0.0
json_serializable: ^2.0.0 #^4.1.1
环顾互联网我发现 Update to/install latest Flutter packages (pubspec.yaml)
最后说在 Flutter 2 中它将有助于运行 1 家扑朔迷离的酒吧已经过时， 2 flutter pub upgrade --major-versions
运行 1 个“flutter pub outdated”会得到大量输出并以：
Changed 75 dependencies!
25 packages have newer versions incompatible with dependency constraints.
Try `flutter pub outdated` for more information.
No changes to pubspec.yaml!
运行 2 "flutter pub upgrade --major-versions" 也给出了很多输出并以：
...
No dependencies changed.
25 packages have newer versions incompatible with dependency constraints.
Try `flutter pub outdated` for more information.
Changed 4 constraints in pubspec.yaml:
json_annotation: ^2.0.0 -> ^4.0.1
rflutter_alert: ^1.1.0 -> ^2.0.2
webview_flutter: ^1.0.7 -> ^2.0.4
json_serializable: ^2.0.0 -> ^4.1.1
pubspec.yaml 更改为：
dependencies:
flutter:
sdk: flutter
http: ^0.12.2
json_annotation: ^4.0.1 #^4.0.1
rflutter_alert: ^2.0.2 #^2.0.2
pdf_flutter: ^1.1.4
syncfusion_flutter_pdfviewer: ^18.4.49-beta
webview_flutter: ^2.0.4 #^2.0.4
flutter_easyloading: ^3.0.0
cupertino_icons: ^1.0.1
dev_dependencies:
flutter_test:
sdk: flutter
build_runner: ^1.0.0
json_serializable: ^4.1.1 #^4.1.1
现在我再次尝试运行我的（旧）项目，结果如下：
Running "flutter pub get" in get_json...
The current Dart SDK version is 2.12.0-29.10.beta.
Because no versions of json_serializable match >4.1.1 <5.0.0 and json_serializable 4.1.1 requires SDK version >=2.12.0 <3.0.0, json_serializable ^4.1.1 is forbidden.
So, because get_json depends on json_serializable ^4.1.1, version solving failed.
pub get failed (1; So, because get_json depends on json_serializable ^4.1.1, version solving failed.)
我尝试了上述内容的许多变体，但我被卡住了。
任何人都可以帮助或指导我朝着正确的方向前进吗？谢谢。
================================
感谢 Ujjwal Raijada。由于网络支持，我得到了 Flutter 2，并没有考虑空安全。但是，我现在已经按照迁移指南进行了详细说明，现在有了以下 pubspec.yaml：
environment:
sdk: '>=2.12.0 <3.0.0'
dependencies:
flutter:
sdk: flutter
http: ^0.13.1
json_annotation: ^4.0.1
rflutter_alert: ^2.0.2
#pdf_flutter: ^1.1.4 # Package pdf_flutter is not null safe and therefore cannot be used ...
syncfusion_flutter_pdfviewer: ^19.1.57-beta
webview_flutter: ^2.0.4
flutter_easyloading: ^3.0.0
cupertino_icons: ^1.0.2
dev_dependencies:
flutter_test:
sdk: flutter
build_runner: ^2.0.1
json_serializable: ^4.1.1
我还按照迁移指南的建议更改了我的代码。所以现在我运行“flutter packages pub run build_runner build”，结果是：
The pubspec.yaml file has changed since the pubspec.lock file was generated, please run "pub get" again.
pub finished with exit code 65
在 pubspec.yaml 中按“pub get”会得到以下结果：
The current Dart SDK version is 2.12.0-29.10.beta.
Because get_json requires SDK version >=2.12.0 <3.0.0, version solving failed.
pub get failed (1; Because get_json requires SDK version >=2.12.0 <3.0.0, version solving failed.)
Process finished with exit code 1
我现在该怎么办？有什么帮助吗？谢谢。