I\'m using the last version of Eclipse, ADT and the newest Android SDK. If I\'m trying to use something in a simple HelloWorld Android project Google Play feature, for instance,
I wasted a lot of time of findout the solution. The core of bug is Android SDK updating went wrong, old version of Eclipse, not enought memory for Eclipse Java Machine (more detailed about memory bug here).
Even I've tryed to update build tools, API, etc. it didn't work. But I just downloaded new SDK and fully reinstalled and this helped. Do not forget to install new Eclipse and ADT. Do not forget about memory increasing in eclipse.ini file.