一、报错信息

---

打开了一个古老的项目 , 运行后报如下错误 ;

Execution failed for task ':app:mergeDebugResources'.
> Could not resolve all files for configuration ':app:_internal_aapt2_binary'.
   > Could not find com.android.tools.build:aapt2:4.1.0-6503028.
     Searched in the following locations:
       - https://jcenter.bintray.com/com/android/tools/build/aapt2/4.1.0-6503028/aapt2-4.1.0-6503028.pom
     If the artifact you are trying to retrieve can be found in the repository but without metadata in 'Maven POM' format, you need to adjust the 'metadataSources { ... }' of the repository declaration.
     Required by:
         project :app

Possible solution:
 - Declare repository providing the artifact, see the documentation at https://docs.gradle.org/current/userguide/declaring_repositories.html

二、解决方案

---

在很久很久以前 , Android 项目的仓库 , 只有 jcenter 库 ;

allprojects {
    repositories {
        jcenter()
    }
}

现在需要两个仓库 : jcenter() 和 google() ;

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