Imagine you have a structure like this:
res/
    drawable-mdpi/image.png
    drawable-hdpi/image.png
    drawable-xhdpi/image.png
    layout/main.xml
    layout-land/main.xml
    layout-xlarge/main.xml
    layout-sw600dp/main.xml
and you want to know, which layout is used.
One way would be to put a value in resources:
res/
    values-mdpi/strange_info.xml with:
        <string name="image_is_from_folder">drawable-mdpi</string>
    values-hdpi/strange_info.xml with:
        <string name="image_is_from_folder">drawable-hdpi</string>
    values-xhdpi/strange_info.xml with:
        <string name="image_is_from_folder">drawable-xhdpi</string>
    values/strange_info.xml with:
        <string name="main_is_from_folder">layout</string>
    values-land/strange_info.xml with:
        <string name="main_is_from_folder">layout-land</string>
    values-xlarge/strange_info.xml with:
        <string name="main_is_from_folder">layout-xlarge</string>
    values-sw600dp/strange_info.xml with:
        <string name="main_is_from_folder">layout-sw600dp</string>
In code you just do
String mainFolderName = context.getResources().getString(R.string.main_is_from_folder);
I have some doubts regarding -Xdpi qualifier, but it should work (not tested). Note that with the above structure you will get "drawable-hdpi" on ldpi devices for image.png.