新建项目失败，出现：

Failed to resolve: com.android.support:appcompat-v7:28.+

如下图：

解决办法：

在project级的build.gradle中添加红框里的内容

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.