R.java
is quite different in Android Studio than it is in Eclipse. Since you say this is an old project, I'm assuming that it was originally from Eclipse. In Eclipse, R.java
is included in the source tree. However, in Android Studio, it is hidden away. From another Stack Overflow answer:
1. build
This has all the complete output of the make
process i.e. classes.dex, compiled classes and resources, etc.
In the Android Studio GUI, only a few folders are shown. The important
part is that your R.java is found here under
build/source/<flavor>/r/<build type(optional)>/<package>/R.java
You shouldn't need to manually interact with R.java
at all. It can be re-generated from the source code. Thus, it is likely that you won't have any problems -- R.java
will be auto-generated and all will be well. If it isn't, try a rebuild of the project.