“R cannot be resolved to a variable”?

http://stackoverflow.com/questions/7824730/r-cannot-be-resolved-to-a-variable

The sample of Google Maps Android API v2 com.example.mapdemo can not find file “R.java”

http://stackoverflow.com/questions/14503168/the-sample-of-google-maps-android-api-v2-com-example-mapdemo-can-not-find-file

Ans: You need to setup these 3 lib correctly.