关于Flutter报Cannot run with sound null safety的解决方法

关于Flutter报Cannot run with sound null safety的解决方法。

flutter sdk 版本升级到2.0或者更高的版本后，运行之前的代码会报错，比如：

• Error: Cannot run with sound null safety, because the following dependencies
  don't support null safety:
  
  - package:flutter_swiper
  - package:flutter_page_indicator
  - package:transformer_page_view
  
  For solutions, see https://dart.dev/go/unsound-null-safety
  
  
  FAILURE: Build failed with an exception.
  

• Launching lib/main.dart on iPhone 13 mini in debug mode...
  lib/main.dart:1
  Xcode build done.                                           20.5s
  Failed to build iOS app
  Error output from Xcode build:
    2022-11-29 22:48:25.409 xcodebuild[74141:17918950] Requested but did not find extension point with identifier Xcode.IDEKit.ExtensionSentinelHostApplications for extension Xcode.DebuggerFoundation.AppExtensionHosts.watchOS of plug-in com.apple.dt.IDEWatchSupportCore
    2022-11-29 22:48:25.410 xcodebuild[74141:17918950] Requested but did not find extension point with identifier Xcode.IDEKit.ExtensionPointIdentifierToBundleIdentifier for extension Xcode.DebuggerFoundation.AppExtensionToBundleIdentifierMap.watchOS of plug-in com.apple.dt.IDEWatchSupportCore
      ** BUILD FAILED **
    Xcode's output:
      Writing result bundle at path:
  	    /var/folders/h5/dd9h9tgx735bfwwqt239pc0w0000gn/T/flutter_tools.sKJxa1/flutter_ios_build_temp_dirBidLby/temporary_xcresult_bundle
    Error: Cannot run with sound null safety, because the following dependencies
  don't support null safety:
   - package:get
  For solutions, see https://dart.dev/go/unsound-null-safety
  Failed to package /Users/mzc/Documents/project_self/planet_of_knowledge.
  Command PhaseScriptExecution failed with a nonzero exit code
  note: Using new build system
  note: Planning
  note: Build preparation complete
  note: Building targets in dependency order
  Result bundle written to path:
  	/var/folders/h5/dd9h9tgx735bfwwqt239pc0w0000gn/T/flutter_tools.sKJxa1/flutter_ios_build_temp_dirBidLby/temporary_xcresult_bundle
  Could not build the application for the simulator.
  Error launching application on iPhone 13 mini.
  Exited (sigterm)
  

解决方案

上面的问题是，这些包不支持 safety模式。

• 我们可以在运行的时候添加--no-sound-null-safety。

  • 打开Android Studio，然后依次选择【Run】 -->【 Edit Configurations】 --> 【Add Additional Run args 】--> 【--no-sound-null-safety】

• 除了上面找个方法外，对于一些老的项目，我们还可以通过降低sdk版本的方式来解决报错，比如

  • 因为sdk 2.12 以上版本有了空安全要求。
  • sdk: ">=2.12.0 < 3.0.0" 改为 sdk: ">=2.8.0 < 3.0.0"