gradle编译的时候出现报错信息：

Cannot create variant 'android-aidl' after configuration ':puree:debugApiElements' has been resolved

意思是不能在debugApiElements标签后面创建变体android-aidl。

解决办法

先看来一段官方解释：

Update Gradle version from 4.1 to 4.4
In Gradle 4.4, it is a bug to resolve a configuration before the lint task is
created ([see [] Therefore, to upgrade
gradle version, we need to change the "generateJavadoc" task to remove using
files() call during initialization phase, but change move this to doFirst()
instead.

大概的意思是说，在4.4版本，这是一个bug。

还有网友也说：

 It seems like it's an error coming from the version of Gradle you're using. You might be able to solve it by downgrading, as it's probably incompatible with a library you're using (which might be this one).

For reference, we're using Gradle version 2.3.3 in this project, so it might be worth giving that one a try.

这是一个bug，会出现在很早的版本里面。

查看网友的解决办法：

I fixed this issue by adding the classpath in the doFirst{ } block in build.gradle of our exoplayer module
alongwith applying the above mentioned fix.

大概是: 将classpath的初始化扔到doFirst里面，然后就能够顺利编译。

博主在项目中也使用这个办法，问题最后得到解决。

参考文章: https://github.com/watson-developer-cloud/android-sdk/issues/78
参考文章：https://blog.csdn.net/u013172664/article/details/88722971
参考文章：https://github.com/google/ExoPlayer/commit/13592dfb53ec99ce1fdb2744e34717dbdec9dea8