Accessing app R class from my Android library

I'm developing a library that needs to access layout items of the app implementing it. The only way I know how to do it is with reflection. In other words, if I create a constructor to my Library API like this:

public MyLibraryAPI(String packageName) {
    Class appR = Class.forName(String.format("%s.R", packageName));
    ...
}

And the developer would instantiate the library with his package name as the parameter in the constructor.

What I ultimately need is to let my inner classes know the Android Views used in the developers layout (.xml files) - both the id and the type. Is there a way to achieve this without reflection and escape the performance overhead? I'm certain it cannot be done, but asking in case there's an expert that sees what I fail to notice.