PermissionBuilder class

class LocationPermissionWidget extends StatelessWidget {
  @override
   Widget build(BuildContext context) {
       return PermissionBuilder(
           permission: Permission.location, // can be any permission in Permission.
           // We didn't ask for permission yet.
           initialBuilder: (_, askPermissionFn) => FirstTimePermissionWidget(),
           // Permission requested. Awaiting for user input. Will rebuild after user input
           requestingBuilder: (_) => RequestingPermissionWidget(),
           // User has granted us permission
           grantedBuilder: (_) => PermissionGrantedWidget(),
           // The OS restricts access, for example because of parental controls
           restrictedBuilder: (_, askPermissionFn) => PermissionRestrictedWidget(),
           //The user opted to never again see the permission request dialog for this app.
           permanentlyDeniedBuilder: (_, askPermissionFn, openSettingsFn) => PermanentlyDeniedWidget(
               requestPermissionFn: askPermissionFn,
               openSettingsFn: openSettingsFn,
           ),
           // User denied the permission once
           deniedBuilder: (_, askPermissionFn, openSettingsFn) => PermissionDeniedWidget(
               openSettingsFn: openSettingsFn,
               requestPermissionFn: askPermissionFn,
           ),
       );
   }
}