code: private int getPermissionIndex(PackageInfo packageInfo, String permissionName) {
      if (packageInfo.requestedPermissions != null) {
        for (int i = 0; i < packageInfo.requestedPermissions.length; i++) {
          if (permissionName.equals(packageInfo.requestedPermissions[i])) {
            return i;
          }
        }
      }
  
      return -1;
    }
docs: Returns the index of the given permission in the PackageInfo.requestedPermissions array, or -1
  if it's not found.