AndroidStudio配置阿里云镜像地址，加速依赖资源下载

背景：

平时安卓项目编译较慢，其中一个原因就是要下载依赖资源包比较慢。为了解决这个问题，可以配置阿里云镜像，加速下载。

配置方法：

1. 对特定项目生效，在项目中的build.gradle修改内容

buildscript {
    repositories {
        maven { url 'http://maven.aliyun.com/nexus/content/groups/public/' }
                maven{ url 'http://maven.aliyun.com/nexus/content/repositories/jcenter'}
    }
    dependencies {
        classpath 'com.android.tools.build:gradle:3.0.1'
    }        
}

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

2. 对所有项目生效

在USER_HOME/.gradle/下创建init.gradle文件，内容如下:

allprojects{
    repositories {
        def ALIYUN_REPOSITORY_URL = 'http://maven.aliyun.com/nexus/content/groups/public'
        def ALIYUN_JCENTER_URL = 'http://maven.aliyun.com/nexus/content/repositories/jcenter'
        all { ArtifactRepository repo ->
            if(repo instanceof MavenArtifactRepository){
                def url = repo.url.toString()
                if (url.startsWith('https://repo1.maven.org/maven2')) {
                    project.logger.lifecycle "Repository ${repo.url} replaced by $ALIYUN_REPOSITORY_URL."
                    remove repo
                }
                if (url.startsWith('https://jcenter.bintray.com/')) {
                    project.logger.lifecycle "Repository ${repo.url} replaced by $ALIYUN_JCENTER_URL."
                    remove repo
                }
            }
        }
        maven {
                url ALIYUN_REPOSITORY_URL
            url ALIYUN_JCENTER_URL
        }
    }
}