Question

Can I assume that R.id file will be present in every android project?

Or is this specific to certain dev environments?

Answer 1

It gets autogenerated by the compiler; you can safely assume it will always exist.

Check the documentation:

A project’s R.java file is an index into all the resources defined in the file.

You use this class in your source code as a sort of short-hand way to refer to resources you’ve included in your project.

This is particularly powerful with the code-completion features of IDEs like Eclipse because it lets you quickly and interactively locate the specific reference you’re looking for.