参数类型 'Stream<dynamic>?'不能分配给参数类型'Stream<QuerySnapshot<Object?>>?'

Question

我正在尝试从 firestore 获取文档，但我收到以下错误

'''

onsearchBtnClick() async {``

isSearching = false;
//setState(() {});
usersStream = await DatabaseMethods()
    .getUserByUserName(searchUsernameEditingController.text);
//setState(() {});}


Widget searchUsersList() {
return StreamBuilder<QuerySnapshot>(
  stream: usersStream,
  builder: (context, snapshot) {
    return snapshot.hasData
        ? ListView.builder(
            itemCount: snapshot.data!.docs.length,
            shrinkWrap: true,
            itemBuilder: (context, index) {
              DocumentSnapshot ds = snapshot.data!.docs[index];
              return Image.network(ds[index]);
            },
          )
        : Center(
            child: CircularProgressIndicator(),
          );
  },
);}Widget chatRoomsList() {
return Container();}

//数据库是

class DatabaseMethods {Future addUserInfoToDB(

  String userId, Map<String, dynamic> userInfoMap) async {
return FirebaseFirestore.instance
    .collection("users")
    .doc(userId)
    .set(userInfoMap);

}

{ Future getUserByUserName(String username) async {

return FirebaseFirestore.instance
    .collection("users")
    .where("username", isEqualTo: username)
    .snapshots();

} }

'''

Answer 1

尝试将getUserByUserName 的返回类型从Future<Stream> 更改为Stream<QuerySnapshot>，而不是将其分配给新变量，而是使用Stream，因为它是stream: DatabaseMethods().getUserByUserName(searchUsernameEditingController.text)

Answer 2

你应该删除 await in

usersStream = await DatabaseMethods().getUserByUserName(searchUsernameEditingController.text);

如果您将 await 用于快照，则它不再是流。

return FirebaseFirestore.instance
    .collection("users")
    .where("username", isEqualTo: username)
    .snapshots();