Lint mark all resources that used the R file as unused

Question

I have an android app on gradle. The structure of the project is as follows:

project
  libs
    ActionBarSherlock
      src
      AndroidManifest.xml
    DragSortListView
      src
      AndroidManifest.xml
    PhotoView-1.2.2
      src
      AndroidManifest.xml  
  app
    build
    libs
    src
      main
        assets
        java
        jniLibs
        res
        AndroidManifest.xml
  lint.xml

I run Lint in my project as follows:

lint app/src/ --config lint.xml --html app/build/lint/report.html

This successfully generates a lint report, but the report contains a warning package

"UnusedResources: Unused resources"
main/res/drawable/my_drawable.xml: The resource R.drawable.my_drawable appears to be unused

In fact, Lint marks every resource that I can access only through the R file. For example, if I have my_layout.xml, which I use in another xml via @ layout / my_layout, everything will be fine. But if I access them only from java code through an R file, for example, R.layout.my_layout lint marks it as "unused"

I tried adding Lint to the input folder with the generated R file from my build directory, like this

lint app/src/ app/biuld/sources/ --config lint.xml --html app/build/lint/report.html

but it does not affect.

Any thoughts and suggestions what's wrong with my line?