I have resolved the problem, My build path wasn't in the project folder. Thanks for your replay, it oriented me.
But there is still no ad in my application (I'm trying to use admob)...
There is 2 errors in my logs, but I'm not sure it's about ads:
DynamiteModule:: java.lang.ClassNotFoundException: Didn't find class "com.google.android.gms.dynamite.DynamiteModule$DynamiteLoaderClassLoader"
ServiceManager: Permission failure: android.permission.BODY_SENSORS from uid=10584 pid=10170