flutter安装目录下，把
/packages/flutter_tools/gradle/flutter.gradle中的
private static final String MAVEN_REPO = "https://storage.googleapis.com/download.flutter.io";改为
private static final String MAVEN_REPO = "https://mirrors.tuna.tsinghua.edu.cn/flutter/download.flutter.io";
修改后保存，重新运行app，等待一点时间，跑起来了，ok!