title: OpenCV 2.4.6 for Android shows errors
body: <p>I am trying to run HelloCV on Android and have been following the doc for OpenCV on Android . Unfortunately I stumbled across this error when I used OpenCV 2.4.6.</p>
  
  <p>Under cleaning all projects , I got theses errors: </p>
  
  <pre><code>Errors occurred during the build.
  Errors running builder 'Android Resource Manager' on project 'OpenCV Library - @OPENCV_VERSION@'.
  java.lang.NullPointerException
  Errors running builder 'Android Resource Manager' on project 'OpenCV Sample - 15 puzzle'.
  java.lang.NullPointerException
  Errors running builder 'Android Resource Manager' on project 'OpenCV Sample - color-blob-detection'.
  java.lang.NullPointerException
  Errors running builder 'Android Resource Manager' on project 'OpenCV Sample - face-detection'.
  java.lang.NullPointerException
  Errors running builder 'Android Resource Manager' on project 'OpenCV Sample - image-manipulations'.
  java.lang.NullPointerException
  Errors running builder 'Android Resource Manager' on project 'OpenCV Sample - native-activity'.
  java.lang.NullPointerException
  Errors running builder 'Android Resource Manager' on project 'OpenCV Tutorial 1 - Camera Preview'.
  java.lang.NullPointerException
  Errors running builder 'Android Resource Manager' on project 'OpenCV Tutorial 2 - Mixed Processing'.
  java.lang.NullPointerException
  Errors running builder 'Android Resource Manager' on project 'OpenCV Tutorial 3 - Camera Control'.
  java.lang.NullPointerException
  Errors running builder 'Android Resource Manager' on project 'OpenCV_JavaAPI_Tests'.
  java.lang.NullPointerException
  </code></pre>
  
  <p>And under building workspace I got these errors;</p>
  
  <pre><code>Errors occurred during the build.
  Errors running builder 'Android Resource Manager' on project 'OpenCV Library - @OPENCV_VERSION@'.
  java.lang.NullPointerException
  Errors running builder 'Android Resource Manager' on project 'OpenCV Sample - 15 puzzle'.
  java.lang.NullPointerException
  Errors running builder 'Android Resource Manager' on project 'OpenCV Sample - color-blob-detection'.
  java.lang.NullPointerException
  Errors running builder 'Android Resource Manager' on project 'OpenCV Sample - face-detection'.
  java.lang.NullPointerException
  Errors running builder 'Android Resource Manager' on project 'OpenCV Sample - image-manipulations'.
  java.lang.NullPointerException
  Errors running builder 'Android Resource Manager' on project 'OpenCV Sample - native-activity'.
  java.lang.NullPointerException
  Errors running builder 'Android Resource Manager' on project 'OpenCV Tutorial 1 - Camera Preview'.
  java.lang.NullPointerException
  Errors running builder 'Android Resource Manager' on project 'OpenCV Tutorial 2 - Mixed Processing'.
  java.lang.NullPointerException
  Errors running builder 'Android Resource Manager' on project 'OpenCV Tutorial 3 - Camera Control'.
  java.lang.NullPointerException
  Errors running builder 'Android Resource Manager' on project 'OpenCV_JavaAPI_Tests'.
  java.lang.NullPointerException
  </code></pre>
  
  <p>Should I try to work with another version of OpenCV , or there are some inherent config problem in my environment . Thanks.</p>