[Solved]-Imported project throws java.lang.ClassNotFoundException-eclipse

i've fairly certain i've seen things like this happen when i haven't imported the code into eclipse, but have tried to run the library from its downloaded location e.g. for google play game services:

import the typeanumber and basegameutils code from the android samples into your workspace. to do this in eclipse: click file > import > android > existing android code into workspace. browse to the directory where you downloaded typeanumber on your development machine and click ok to import the files. perform the same steps for basegameutils.

(i got this from https://developers.google.com/games/services/android/quickstart)

also ,although this is not an exact fit for your problem:

google player game service error: can't build the sample game