Studio报错：Re-download dependencies and sync project (requires network)

//我是学习recyclerview控件时出现的错误

修改项目根目录下 build.gradle 文件，将 jcenter() 或者 mavenCentral() 替换掉即可。可以用国内的仓库代替：

• 阿里的仓库地址：http://maven.aliyun.com/nexus/content/groups/public/
• OSChina的仓库地址：http://maven.oschina.net/content/groups/public/

buildscript {
    
    repositories {
    maven{ url 'http://maven.aliyun.com/nexus/content/repositories/central/'}
        google()
        jcenter()
    }
    dependencies {
        classpath 'com.android.tools.build:gradle:3.1.4'
        

        // 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/repositories/central/'}
        google()
        jcenter()
    }
}

task clean(type: Delete) {
    delete rootProject.buildDir
}