title: Proguard + zxing, My APK doesn't shrink
body: <p>Hi I'm building an android app that uses zxing library for QR Scanning only.</p>
  
  <p>I'm using <a href="https://code.google.com/p/zxing/source/browse/trunk/android/proguard-android-optimize.txt?r=2382" rel="nofollow">zxing'S proguard file</a> file to shrink and optimize the APK, without success.
  My APK always ends up with 133 M of size.</p>
  
  <p>Proguard outputs several warnings stating that some class references are missing (some of them are from rt.jar). I've get rid 
  of them with: -ignorewarnings</p>
  
  <p>(Maybe this is the problem the APK isn't shrinking)</p>
  
  <p>How can I make the APK to shrink?
  Thanks in advance!</p>