RavenProject/ravenwallet-android

Total Newbie trying to understand the source code to Ravencoin android wallet: RavenProject/ravenwallet-android

In WalletMaster.java (and other files) there is an "import com.ravenwallet.R". But there is no such file or class that can be resolved . Can anybody explain to me as if I was a semi-sentient child what's going on? 😀