How to access resource with dynamic name in my case?

int id = getResources().getIdentifier(imageName, type, package);

This will get you the ID of the resource you are looking for. With it, you can then access the resource from the R class.

Using only the name parameter:

You can also include all the 3 info in the "name" parameter using the following format: "package:type/image_name", something like:

int id = getResources().getIdentifier("com.my.app:drawable/my_image", null, null);

This is useful when you're working with external components or libraries that you can't, or don't want to, change how getIdentifier() is called. e.g.: AOSP Launcher3

Try this:

int id = getResources().getIdentifier(imageName, "drawable", getPackageName());