Android Studio 初始化build.gradle下载资源失败

// Top-level build file where you can add configuration options common to all sub-projects/modules.

buildscript {
    repositories {
        maven{ url 'http://maven.aliyun.com/nexus/content/groups/public/'}
        google()
        }
    dependencies {
        classpath 'com.android.tools.build:gradle:3.3.0-beta03'

        // 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() }
}

以上是本人使用的build.gradle内容，测试使用正常。