解决Could not resolve all artifacts for configuration ':classpath'.

解决：在项目外部的build.gradle中增加

maven { url 'http://maven.aliyun.com/nexus/content/groups/public/' }

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

    }
    dependencies {
        classpath 'com.android.tools.build:gradle:3.2.1'

        // NOTE: Do not place your application dependencies here; they belong
        // in the individual module build.gradle files
    }
}

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