解决：Direct local .aar file dependencies are not supported when building an AAR.

Android Studio 4.0+版本在打包过程中抛出以下异常

Direct local .aar file dependencies are not supported when building an AAR. 
The resulting AAR would be broken because the classes and Android resources from any local .aar file dependencies would not be packaged in the resulting AAR. 
Previous versions of the Android Gradle Plugin produce broken AARs in this case too (despite not throwing this error). 
The following direct local .aar file dependencies of the :XXXXXXXXXX

解决方案如下：

1.新建一个module，主要保留build.gradle文件（其他文件可以删掉）

2.将“The following direct local .aar file dependencies of the :”后提示的aar文件放到新建的module的根目录中，module目录结构如下：

3.修改build.gradle文件内容，如下：

configurations.maybeCreate("default")
artifacts.add("default", file('xxxx.aar'))

// 如有多个aar，只需要再次add
//artifacts.add("default", file('xxxx2.aar'))
//......
//artifacts.add("default", file('xxxxn.aar'))

4.将原aar的module去以module的形式依赖新module，依赖形式为 compileOnly，如下：

dependencies {
    ...    
    compileOnly project(path: ':newmodule')
    ...
}

5.再次打包即可

如有问题欢迎留言~