lib/photo_list_screen.dart_cf
class PhotoListScreen extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    final User user = FirebaseAuth.instance.currentUser!;
    return Scaffold(
      body: StreamBuilder<QuerySnapshot<Map<String, dynamic>>>(
        stream: FirebaseFirestore.instance
            .collection('users/${user.uid}/photos')
            .snapshots(),
        builder: (context, snapshot) {
          final QuerySnapshot query = snapshot.data!;
          final List<String> imageList = query.docs
              .map((doc) => doc.get('imageURL') as String)
              .toList();
          return GridView.count(
            crossAxisCount: 2,
            children: imageList.map((imageURL) {
              return Image.network(imageURL);
            }).toList(),
          );
        },
      ),
    );
  }
}