Flutter build method keeps rebuilding a referenced method that's in another file

Apologies if I am articulating it poorly but I have a main file called

Homescreen.dart

Two other files called

category_builder.dart

and

post_builder.dart respectively.

In my homescreen file I have a scaffold being returned that has an app bar and a body. Now in the body I have a listview builder that builds my home screen with categories on the top and posts below it.

For ref heres my home screen code:

body: FutureBuilder(
        future: FirebaseFirestore.instance
            .collection('posts')
            .orderBy('createdDate', descending: true)
            .get(),
        builder: (context, snapshot) {
          if (snapshot.hasData) {
            return SizedBox(
              child: ListView.builder(
                shrinkWrap: true,
                itemCount: snapshot.data!.docs.length,
                itemBuilder: (context, index) {
                  if (index == 0) {
                    return Column(
                      children: [
                        Container(
                          width: MediaQuery.of(context).size.width,
                          padding: const EdgeInsets.fromLTRB(20, 10, 20, 0),
                          child: Row(
                            children: const [
                              Icon(
                                Icons.newspaper_outlined,
                                color: active,
                              ),
                              SizedBox(
                                width: 10,
                              ),
                              Text(
                                'Boards',
                                style: TextStyle(
                                    color: highlights,
                                    fontSize: 16,
                                    fontWeight: FontWeight.bold),
                              ),
                            ],
                          ),
                        ),
                        SizedBox(
                          width: MediaQuery.of(context).size.width,
                          height: 95,
                          child: const BuildCat(),
                        ),
                        const SizedBox(
                          height: 5,
                        ),
                      ],
                    );
                  }
                  //index -= 1;
                  return SizedBox(
                    width: double.infinity,
                    child: PostBuilder(
                        postCallack: snapshot.data!.docs[index].data()),
                  );
                },
              ),
            );
          } else {
            return const Center(
                child: CircularProgressIndicator(
              color: Colors.white,
            ));
          }
        },
      ),

Now every time I scroll down at the bottom of the list, and when I scroll back up the category list is rebuild and reloaded, which is something I'm trying to avoid. I did try different thinks such as storing it in a variable and initializing it in initstate, initializing the Firestore query in the state of the stateful widget. But noting worked. Any help will be much apprectiated.

Also heres whats in Category file:

class BuildCat extends StatefulWidget {
  const BuildCat({super.key});

  @override
  State<BuildCat> createState() => _BuildCatState();
}

class _BuildCatState extends State<BuildCat> {
  List? catDataList;

  @override
  void initState() {
    // TODO: implement initState
    super.initState();
    catdata();
  }

  Future<void> catdata() async {
    await FirebaseFirestore.instance
        .collection('boards')
        .doc('Boards')
        .get()
        .then((value) => catDataList = value.data()!['BoardsList']);
    setState(() {
      catDataList;
    });
  }

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      body: ListView.separated(
          shrinkWrap: true,
          scrollDirection: Axis.horizontal,
          padding: const EdgeInsets.all(10),
          itemBuilder: (context, index) {
            if (catDataList == null) {
              return const Center(
                child: CircularProgressIndicator(color: Colors.white),
              );
            }

            return BuildCard(
                catDataList![index]['id'], catDataList![index]['img']);
          },
          separatorBuilder: (context, index) {
            return const SizedBox(width: 10);
          },
          itemCount: catDataList == null ? 0 : catDataList!.length),
    );
  }
}