终于找到了

FirestoreQueryBuilder<Map<String, dynamic>>(
                query: usersQuery,
                builder: (context, snapshot, _) {
                  // ...
                  return ListView.builder(
                    itemCount: snapshot.docs.length +1,
                    itemBuilder: (context, index) {
                      // if we reached the end of the currently obtained items, we try to
                      // obtain more items
                      if (snapshot.hasMore &&
                          index + 1 == snapshot.docs.length) {
                        // Tell FirestoreQueryBuilder to try to obtain more items.
                        // It is safe to call this function from within the build method.
                        snapshot.fetchMore();
                      }
                      if (index == 0) {
                        return Container(
                          color: Colors.red,
                          height: 100,
                        );
                      } else {
                        final user = snapshot.docs[index -1].data();
                        return FeedBox(
                          imageUrl: user['imageUrl'],
                        );
                      }
                    },
                  );
                },
              )