The flutter SDK is incomplete=Flutter SDK 安装不完整

1. 进入flutter/bin目录
2. 打开cmd/gitbash/powershell
3. 执行：

./flutter doctor

一定要带前面的 **./ **否则提示 flutter: command not found

可以看到命令行中出现：

Checking Dart SDK version...
Downloading Dart SDK from Flutter engine ...
Expanding downloaded archive...
Building flutter tool...
Running pub upgrade...

执行完毕后，就可以正常使用flutter了。