title: R cannot be resolved to a variable (new android project)
body: <p>This happens for a new project too!</p>
  
  <p>The gen folder is empty.
  No errors in activity_main.xml file.</p>
  
  <p>I have tried:</p>
  
  <ul>
  <li>Project->Clean</li>
  <li>Project->Properties-> check android version</li>
  <li>Project->Build</li>
  <li>Re installing eclipse (latest)</li>
  <li>Re installing ADT plugin (latest)</li>
  <li>commenting lines: 
     setContentView(R.layout.activity_main);
  and
     getMenuInflater().inflate(R.menu.main, menu);
  and building project</li>
  </ul>
  
  <p>but still the gen folder is empty!
  help!</p>