1.按照下面的地址步骤执行：
https://flutterchina.club/get-started/install/
1.png
2.注意添加环境变量的时候大写部分为key，等号后面为value:
PUB_HOSTED_URL = https://pub.flutter-io.cn
FLUTTER_STORAGE_BASE_URL = https://storage.flutter-io.cn
3.如果执行flutter doctor命令出现如下异常：
Some Android licenses not accepted. To resolve this, run: flutter doctor --android-licens
则执行如下命令并一直输入y即可：
flutter doctor --android-licenses
