public static function String getVersionName(Context context, Class cls) 
{
  try {
    ComponentName comp = new ComponentName(context, cls);
    PackageInfo pinfo = context.getPackageManager().getPackageInfo(comp.getPackageName(), 0);
    return pinfo.versionName;
  } catch (android.content.pm.PackageManager.NameNotFoundException e) {
    return null;
  }
}