old for andorid studio/gradle:
maven { url "http://maven.aliyun.com/nexus/content/groups/public/" }
new for andorid studio/gradle:
maven { url "https://maven.aliyun.com/repository/public/" }
查看阿里云仓库列表：
https://maven.aliyun.com/mvn/view
阿里云仓库列表：
public repository
https://maven.aliyun.com/repository/public
google repository
https://maven.aliyun.com/repository/google
gradle-plugin repository
https://maven.aliyun.com/repository/gradle-plugin
jcenter repository
https://maven.aliyun.com/repository/jcenter
releases repository
https://maven.aliyun.com/repository/releases
spring repository
https://maven.aliyun.com/repository/spring
spring-plugin repository
https://maven.aliyun.com/repository/spring-plugin
说明：
public库是group库，其实代理了maven central和jcenter仓库
你可以浏览proxy库central或jcenter的内容，凡是里面有的包都可以通过public库下载。