title: 'R cannot be resolved to a variable' - gen folder is empty
body: <p>I've got an error:</p>
  
  <pre><code>R cannot be resolved to a variable
  </code></pre>
  
  <p>in line:</p>
  
  <pre><code>setContentView(R.layout.main);
  </code></pre>
  
  <p>but I can't resolve it doing things that other users wrote should be tried, which are:</p>
  
  <ol>
  <li>Getting rid of 'import android.R' line.</li>
  <li>Cleaning the project and then building it again.</li>
  <li>Closing project and then opening it again.</li>
  <li>Going to Project Properties > Java Build Path > Tick Android Version Checkbox</li>
  <li>Following the procedure: Uncheck Project->Build Automatically Project->Properties->Builders: Make sure all Android (3) and Java (1) builders are checked (and nothing more) Window->Preferences->Android->Build: Check "Automatically refresh Resources and Assets folder on build" Right-click on project->Android Tools->Fix Project Settings (not sure what it actually does, but it can't hurt)</li>
  <li>Some users advice to check if .xml files are correct. I don't know how I could do that. I must admit I'm new to java and android programming, and I haven't even written a single line in my project - the code has been generated automaticly.</li>
  <li>Layout xml file is named using lower-case letters.</li>
  <li>No error in resource files (no red-crosses).</li>
  </ol>
  
  <p>layout main.xml file:</p>
  
  <pre><code>&lt;?xml version="1.0" encoding="utf-8"?&gt;
  &lt;LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
      android:layout_width="fill_parent"
      android:layout_height="fill_parent"
      android:orientation="vertical" &gt;
  
      &lt;TextView
          android:layout_width="fill_parent"
          android:layout_height="wrap_content"
          android:text="@string/hello" /&gt;
  
  &lt;/LinearLayout&gt;
  </code></pre>
  
  <p>Thanks in advance for your help!</p>