title: R.java not generated after ADT update
body: <p>I update my android tools and also my ADT. I cleaned my project and build it again. However after this action my /gen folder is empty.</p>
  
  <p>I have made sure that none of my resource contains errors and also made sure that there is no import.R in my activity. I tried cleaning and rebuilding other projects as well with same error. I created a new android project and even the new project had and empty /gen folder.</p>
  
  <p><strong>Solved:
  After the update you need to restart the SDK manager and download android build tools. After i clean my projects everything is fine again. Thank you guys.</strong></p>