在用户变量的Path里添加：E:\src\flutter\bin

https://flutter.dev/community/china
系统属性->环境变量->用户变量
PUB_HOSTED_URL=https://pub.flutter-io.cn
FLUTTER_STORAGE_BASE_URL=https://storage.flutter-io.cn

提示 "improt 'package:flutter/material.dart' not exit"，网上搜索了下解决办法，只需在项目目录，打开终端,运行 flutter packages get