新建项目失败，出现：
Failed to resolve: com.android.support:appcompat-v7:28.+
如下图：
报错截图
解决办法：
在project级的build.gradle中添加红框里的内容
build.gradle
错误产生原因：
Starting from version 26 of support libraries make sure that the repositories section includes a maven section with the "https://maven.google.com" endpoint.
