Including android library in flutter app - Plugin with id 'com.android.library' not found

I'm creating a flutter ebook reader app using a package named epub_viewer that uses Folioreader for reading ebooks. but I need to make some customizations in the main library Folioreader for my project so I've tried to add Folioreader as a library for making my customizations and testing the package.

this is the original ebpub_viewer build.gradle dependencies part:

dependencies {
    implementation "com.jideguru:folioreader:0.6.2"
    .....
}

So i changed this to :

dependencies {
    //implementation "com.jideguru:folioreader:0.6.2"
      implementation project(':folioreader')
   ....
}

And putting the Folioreader inside the project using android studio module import but i got some errors:

Build file '/home/user/Applications/flutter/.pub-cache/hosted/pub.dartlang.org/epub_viewer-0.2.5/folioreader/build.gradle' line: 1

A problem occurred evaluating project ':folioreader'.
> Plugin with id 'com.android.library' not found.

Can anybody guide me on how to solve this problem? or maybe a better solution for editing Folioreader from and source and test it in the final flutter app? thanks.