Text widget not updating inside StreamBuilder - flutter

Question

I am getting a QuerySnapShot from a Firestore subcollection inside a StreamBuilder from another query, as follows:
//ver fuegos
var estePost = listaFiltrada[indexPost].post_id;
int numero_fuegos = 0;
FirebaseFirestore.instance
.collection('posts')
.doc(estePost)
.collection('fuegos')
.get()
.then((value) => {
if (value.size > 0)
{
setState(() {
numero_fuegos = value.size;
}),
print("tiene fuegos: " +
numero_fuegos.toString()),
}
else
{
setState(() {
numero_fuegos = value.size;
}),
}
});
There are 3 items for value.size.
Here you have the print output:
I/flutter (29797): tiene fuegos: 3
The issue is that putting the variable numero_fuegos inside a text widget, the output is always 0.
EDIT:
class ListaPosts extends StatefulWidget {
#override
_ListaPostsState createState() => _ListaPostsState();
}
class _ListaPostsState extends State<ListaPosts> {
String _miId = "";
#override
initState() {
// TODO: implement initState
super.initState();
FirebaseAuth.instance.idTokenChanges().listen((User user) {
if (user == null) {
} else {
setState(() {
_miId = user.uid;
});
}
});
}
#override
Widget build(BuildContext context) {
final postsProvider = Provider.of<PostsProvider>(context);
return Container(
color: Colors.transparent,
child: Padding(
padding: const EdgeInsets.only(top: 0.0),
child: Column(
children: [
StreamBuilder<List<Post>>(
stream: postsProvider.posts,
builder: (context, snapshot) {
if (snapshot.data != null &&
snapshot.data.isNotEmpty &&
ConnectionState.done != null) {
List<Post> listaInicial = snapshot.data;
List<Post> listaFiltrada = [];
listaFiltrada = listaInicial;
return Padding(
padding: const EdgeInsets.all(0.0),
child: SizedBox(
width: MediaQuery.of(context).size.width,
height: MediaQuery.of(context).size.height - 140,
child: ListView.builder(
itemCount: listaFiltrada.length,
itemBuilder: (context, indexPost) {
bool es_ambassador = listaFiltrada[indexPost]
.post_autor_is_ambassador;
//ver fuegos
var estePost = listaFiltrada[indexPost].post_id;
int numero_fuegos = 0;
FirebaseFirestore.instance
.collection('posts')
.doc(estePost)
.collection('fuegos')
.get()
.then((value) => {
if (value.size > 0)
{
numero_fuegos = value.size,
print("tiene fuegos: " +
numero_fuegos.toString()),
print("tiene fuegos: " +
value.size.toString()),
}
else
{
setState(() {
numero_fuegos = value.size;
}),
}
});
And that is the Stream:
//Get Posts Entries
Stream<List<Post>> getPosts() {
return _db
.collection('posts')
.orderBy("post_fecha", descending: true)
.snapshots()
.map((snapshot) =>
snapshot.docs.map((doc) => Post.fromJson(doc.data())).toList());
}