AS报错： Could not resolve com.android.support:appcompat-v7:28.0.0

Android Studio在build的时候提示如下错误：

 Could not resolve com.android.support:appcompat-v7:28.0.0.

解决方法应该是在project级别的build.gradle下添加国内镜像，如下：

allprojects {
    repositories {
        jcenter()
        google()
        maven { url'http://maven.aliyun.com/nexus/content/groups/public/'}
    }
}