Stream<QuerySnapshot> 返回空文档

Posted 2023-02-23

【中文标题】Stream<QuerySnapshot> 返回空文档

【英文标题】：Stream<QuerySnapshot> returns null documents

【发布时间】：2020-10-24 06:40:28

【问题描述】：

我对 Flutter 和 cloud-firestore 有疑问。我的数据库连接正常，我可以创建新条目，但我的 Stream 返回空文档。

我的 database.dart 类：

final CollectionReference idCollection = Firestore.instance.collection("idCollection");

Future addId(String idName) async 
    return await idCollection
        .document(uid)
        .collection("userIds")
        .document(idName)
        .setData(
      'key': uid + _randomString(6),
    );


Stream<QuerySnapshot> get ids 
   return idCollection.snapshots();

实际上我希望快照属于以下内容，但由于顶部集合已经抛出 null 错误，我不确定问题出在哪里。

 Stream<QuerySnapshot> get ids 
   return idCollection
        .document(uid)
        .collection("userIds").snapshots();

包装提供者的类

    return StreamProvider<QuerySnapshot>.value(
      value: DatabaseService().ids,

错误和引发错误的类：

════════ Exception caught by widgets library ═══════════════════════════════════
The getter 'documents' was called on null.
Receiver: null
Tried calling: documents
The relevant error-causing widget was
    IdList 
lib\…\home\home.dart:39
════════════════════════════════════════════════════════════════════════════════

class _IdListState extends State<IdList> 
  @override
  Widget build(BuildContext context) 
    final ids = Provider.of<QuerySnapshot>(context);

    for (var doc in ids.documents) 
      print(doc.data);
    

    return Scaffold(
      body: Center(
        child: Text("sdf"),
      ),
    );
  


class IdList extends StatefulWidget 
  @override
  State<IdList> createState() => _IdListState();

提前致谢！

【问题讨论】：

如果为 null 表示您的收藏中没有数据。按预期工作

【参考方案1】：

这是使用 querysnapshot 查询数据库的方法

    Future _getUsers() async 
     QuerySnapshot querySnapshot = await Firestore.instance
            .collection('idCollection')
            //you may want to sort your data here 
           
            .getDocuments();
        print('###########s result $querySnapshot.documents');

  if (querySnapshot != null) 
      for (int i = 0; i < querySnapshot.documents.length; i++) 
        var a = querySnapshot.documents[i];
        print(a.documentID);
 setState(() 
          documentId = a.documentID;
         userID = a.data['userId'];
        
        );