title: Android apk obfuscation
body: <p>I am trying to obfuscate my android application. But not able to achieve the result.</p>
  
  <p>In the tool it prompts "The input doesn't contain any classes. Did you specify the proper '-injars' options?"</p>
  
  <p>So, does it mean my input file is already obfuscated? How do I differentiate between a normal APK and an obfuscated APK? </p>
  
  <p>Any help will be highly appreciated.</p>