如何限制来自Firestore的数据

Question

我想显示来自Firebase Firestore的最新数据。我只需要最新的3个文档。我确实尝试了ListView中的ItemCount，但它不起作用，并且也崩溃了。任何帮助将不胜感激。预先感谢您，如果架子架的架子不像我的代码那样长，则不接受我的问题。

class NewInHouses extends StatefulWidget {
  const NewInHouses({Key? key}) : super(key: key);

  @override
  State<NewInHouses> createState() => _NewInHousesState();
}
class _NewInHousesState extends State<NewInHouses> {
  final Stream<QuerySnapshot> _usersStream =
      FirebaseFirestore.instance.collection('houseRent').snapshots();
  @override
  Widget build(BuildContext context) {
    return StreamBuilder<QuerySnapshot>(
      stream: _usersStream,
      builder: (BuildContext context, AsyncSnapshot<QuerySnapshot> snapshot) {
        if (snapshot.hasError) {
          return const Text('Something went wrong');
        }
        if (snapshot.connectionState == ConnectionState.waiting) {
          return const Text("Loading");
        }
        return Padding(
          padding: const EdgeInsets.all(5.0),
          child: Container(
            height: 160,
            width: 2000,
            color: Colors.white.withOpacity(0),
            child: ListView(
              scrollDirection: Axis.horizontal,
              children: snapshot.data!.docs.map((DocumentSnapshot document) {
                Map<String, dynamic> data =
                    document.data()! as Map<String, dynamic>;
                return Padding(
                  padding: const EdgeInsets.fromLTRB(0, 2.5, 10, 2.5),
                  child: Container(
                    height: 150,
                    width: 300,
                    decoration: const BoxDecoration(
                        color: Colors.white,
                        borderRadius: BorderRadius.all(Radius.circular(5)),
                        boxShadow: [
                          BoxShadow(
                            color: Colors.grey,
                            spreadRadius: 1,
                            blurRadius: 1,
                          )]),
                    child: Row(
                      children: [
                        Container(
                          width: 150,
                          decoration: BoxDecoration(
                            color: Colors.white,
                            borderRadius: const BorderRadius.only(
                              topLeft: Radius.circular(5),
                              bottomLeft: Radius.circular(5),),
                            image: DecorationImage(
                              image: CachedNetworkImageProvider(
                                data["1stpic"],),
                            ),),),
                        Padding(
                          padding: const EdgeInsets.all(8.0),
                          child: Column(
                            children: [
                              Text(
                                data["rooms"] +
                                    " Beds  " +
                                    data["baths"] +
                                    " Baths",
                                style: TextStyle(
                                    fontFamily: "eng",
                                    fontWeight: FontWeight.bold,
                                    color: Colors.blue.shade900,
                                    fontSize: 12),
                              ),],),),],),),);}).toList(),),),);}, ); }}

Answer 1

用

final Stream<QuerySnapshot> _usersStream =
      FirebaseFirestore.instance.collection('houseRent').snapshots();

​

final Stream<QuerySnapshot> _usersStream =
FirebaseFirestore.instance.collection('houseRent').orderBy('your-field-name', descending: true).limit(3).snapshots();

Answer 2

您可以在.collection（'Houserent'）之后添加。 /code>您可以下降它，以便最后一个位于顶部。