Repo: google()

在Android Studio 中的项目根目录下，build.gradle:

allprojects {
    repositories {
        jcenter()
        google()
    }
}

其中google()的配置，是在Android Studio 3.0，Gradle版本3.0.0以上，才可以使用的。其对应 Android Maven Repository

该仓库目前有：

android.arch.core
android.arch.lifecycle
android.arch.paging
android.arch.persistence
android.arch.persistence.room
com.android.databinding
com.android.java.tools.build
com.android.support
com.android.support.constraint
com.android.support.test
com.android.support.test.espresso
com.android.support.test.espresso.idling
com.android.support.test.janktesthelper
com.android.support.test.services
com.android.support.test.uiautomator
com.android.tools
com.android.tools.analytics-library
com.android.tools.build
com.android.tools.ddms
com.android.tools.external.com-intellij
com.android.tools.external.org-jetbrains
com.android.tools.internal.build.test
com.android.tools.layoutlib
com.android.tools.lint
com.crashlytics.sdk.android
com.google.android.gms
com.google.android.instantapps
com.google.android.instantapps.thirdpartycompat
com.google.android.support
com.google.android.wearable
com.google.firebase
com.google.gms
io.fabric.sdk.android

在网站上，点击对应项，能查看到其所有可依赖的版本号

比如，要依赖com.android.support下的customtabs：

- com.android.support
	+ animated-vector-drawable
	+ appcompat-v7
	+ cardview-v7
	+ customtabs
           23.0.0
           23.0.1
           23.1.0
           23.1.1
           ...
           26.0.0
           ...
       ...
...

依赖的格式：group:name:version

例：implementation 'com.android.support:customtabs:26.0.0'

Repo: maven-aliyun

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

使用国内镜像aliyun的 maven仓库