title: why classes.dex file changed after I repacked the apk?
body: <p>I repacked the apk file with apktool, but I didn't change anything.
  I know that repacking the apk will cause the signature changed, but I don't understand why classes.dex file will change?(Because the sha-1 value of classes.dex in META-INF/Manifest.MF has changed, but I didn't change the code.) </p>
  
  <p>Does 'apktool d XXX.apk' will change the code? Where does it change?
  Can somebody explain the reason to me ?</p>