Flutter SDK version is 0.0.0-unknown

这个问题应该是Flutter没有装好，我将本地的flutter删除后重新按照以下步骤安装就好了

https://flutter.dev/docs/get-started/install/macos  这是官方安装文档

1. 

git clone https://github.com/flutter/flutter.git -b stable

2. 

 export PATH="$PATH:`pwd`/flutter/bin"

3. 

flutter precache

 4. 

flutter doctor