VS Code运行Flutter默认应用编译崩溃，提示空值检查运算符错误

问题说明 #

刚接触Flutter，在Visual Studio Code中运行默认Flutter应用时失败，报错信息如下：

Crash when compiling null,
at character offset null:
Null check operator used on a null value
#0      InferableTypeBuilderMixin.type (package:front_end/src/fasta/builder/type_builder.dart:392:29)
#1      InferableTypeBuilder.inferType (package:front_end/src/fasta/builder/omitted_type_builder.dart:155:12)
#2      SourceLoader.performTopLevelInference (package:front_end/src/fasta/source/source_loader.dart:2358:19)
#3      KernelTarget.buildOutlines.<anonymous closure> (package:front_end/src/fasta/kernel/kernel_target.dart:532:14)
<asynchronous suspension>
#4      withCrashReporting (package:front_end/src/fasta/crash.dart:122:12)
<asynchronous suspension>
#5      _buildInternal (package:front_end/src/kernel_generator_impl.dart:139:7)
<asynchronous suspension>
#6      withCrashReporting (package:front_end/src/fasta/crash.dart:122:12)
<asynchronous suspension>
#7      generateKernel.<anonymous closure> (package:front_end/src/kernel_generator_impl.dart:47:12)
<asynchronous suspension>
#8      generateKernel (package:front_end/src/kernel_generator_impl.dart:46:10)
<asynchronous suspension>
#9      kernelForModule (package:front_end/src/api_prototype/kernel_generator.dart:100:11)
<asynchronous suspension>
#10     SingleShotCompilerWrapper.compileInternal (file:///C:/b/s/w/ir/cache/builder/sdk/pkg/vm/bin/kernel_service.dart:412:11)
<asynchronous suspension>
#11     Compiler.compile.<anonymous closure> (file:///C:/b/s/w/ir/cache/builder/sdk/pkg/vm/bin/kernel_service.dart:221:45)
<asynchronous suspension>
#12     _processLoadRequest (file:///C:/b/s/w/ir/cache/builder/sdk/pkg/vm/bin/kernel_service.dart:914:37)
<asynchronous suspension>


#0      InferableTypeBuilderMixin.type (package:front_end/src/fasta/builder/type_builder.dart:392:29)
#1      InferableTypeBuilder.inferType (package:front_end/src/fasta/builder/omitted_type_builder.dart:155:12)
#2      SourceLoader.performTopLevelInference (package:front_end/src/fasta/source/source_loader.dart:2358:19)
#3      KernelTarget.buildOutlines.<anonymous closure> (package:front_end/src/fasta/kernel/kernel_target.dart:532:14)
<asynchronous suspension>
#4      withCrashReporting (package:front_end/src/fasta/crash.dart:122:12)
<asynchronous suspension>
#5      _buildInternal (package:front_end/src/kernel_generator_impl.dart:139:7)
<asynchronous suspension>
#6      withCrashReporting (package:front_end/src/fasta/crash.dart:122:12)
<asynchronous suspension>
#7      generateKernel.<anonymous closure> (package:front_end/src/kernel_generator_impl.dart:47:12)
<asynchronous suspension>
#8      generateKernel (package:front_end/src/kernel_generator_impl.dart:46:10)
<asynchronous suspension>
#9      kernelForModule (package:front_end/src/api_prototype/kernel_generator.dart:100:11)
<asynchronous suspension>
#10     SingleShotCompilerWrapper.compileInternal (file:///C:/b/s/w/ir/cache/builder/sdk/pkg/vm/bin/kernel_service.dart:412:11)
<asynchronous suspension>
#11     Compiler.compile.<anonymous closure> (file:///C:/b/s/w/ir/cache/builder/sdk/pkg/vm/bin/kernel_service.dart:221:45)
<asynchronous suspension>
#12     _processLoadRequest (file:///C:/b/s/w/ir/cache/builder/sdk/pkg/vm/bin/kernel_service.dart:914:37)
<asynchronous suspension

已知情况：

• 应用在Android Studio可正常运行
• flutter doctor检测无异常
• 已在VS Code安装Flutter和Dart扩展

解决方案 #

• 清理VS Code缓存：关闭VS Code，删除对应系统的缓存目录（Windows：%APPDATA%\Code\Cache、%APPDATA%\Code\CachedData；macOS：~/Library/Caches/Code、~/Library/Application Support/Code/CachedData；Linux：~/.config/Code/Cache、~/.config/Code/CachedData），重启后重试。
• 重置Dart/Flutter扩展设置：打开VS Code设置（快捷键Ctrl+,/Cmd+,），确认Dart: Sdk Path指向正确的Flutter SDK内Dart目录，随后重置扩展设置，重启VS Code。
• 重新生成依赖：在项目根目录终端执行flutter clean和flutter pub get，完成后重新运行项目。
• 更新VS Code及扩展：检查VS Code和Flutter、Dart扩展是否为最新版本，更新后重试。
• 切换Flutter通道：执行flutter channel stable和flutter upgrade，切换到稳定版后重试。

内容的提问来源于stack exchange，提问作者NKS