从 Firestore 集合中获取数据 snapshot.hasdata 返回 Null

Question

所以我一直在关注 YouTube 的教程，当我尝试通过 Stream 快照从名为“users”的集合中获取“用户名”时，它返回 null。

目的：当点击带有用户名的搜索按钮时显示可用的用户。

下面是代码：

  bool isSearching = false;
  Stream? usersStream;

  TextEditingController searchUsernameEditingController =
      TextEditingController();

  onSearchBtnClick() async {
    isSearching = true;
    setState(() {});
    usersStream = await DatabaseMethods()
        .getUserByUsername(searchUsernameEditingController.text);
        
    setState(() {});
  }

  Widget searchUserList() {
    return StreamBuilder(
        stream: usersStream,
        builder: (context, AsyncSnapshot snapshot) {
          return snapshot.hasData
              ? ListView.builder(
                  itemCount: snapshot.data.docs.length,
                  itemBuilder: (context, index) {
                    DocumentSnapshot ds = snapshot.data.docs[index];
                    return Image.network(ds["imgUrl"]);
                  })
              : Center(child: Text("No Users Found"));
        });
  }

来自 DatabaseMethods()：

Future<Stream<QuerySnapshot>> getUserByUsername(String username) async {
    return FirebaseFirestore.instance
        .collection("users")
        .where("username", isEqualTo: username)
        .snapshots();
  }

始终显示“未找到用户”消息

Answer 1

首先确认在调用 onSearchBtnClick 时释放了 streambuilder 的新值。

试试这个。

onSearchBtnClick() async {
  isSearching = true;
  setState(() {});
}

Widget searchUserList() {
  return StreamBuilder(
    stream: DatabaseMethods()
        .getUserByUsername(searchUsernameEditingController.text),
    builder: (context, AsyncSnapshot snapshot) {
      print('called');
      // confirm that print is called when onSearchBtnClick is called.
      return snapshot.hasData
          ? ListView.builder(
              itemCount: snapshot.data.docs.length,
              itemBuilder: (context, index) {
                DocumentSnapshot ds = snapshot.data.docs[index];
                return Image.network(ds["imgUrl"]);
              })
          : Center(child: Text("No Users Found"));
    },
  );
}