颤振问题：“时间戳”类型不是“日期时间”类型的子类型

Posted 2023-02-23

【中文标题】颤振问题：“时间戳”类型不是“日期时间”类型的子类型

【英文标题】：Flutter issue: type 'Timestamp' is not a subtype of type 'DateTime'

【发布时间】：2019-08-05 19:04:12

【问题描述】：

我正在为我的团队和我正在开发的应用寻求帮助。数周以来我们都面临以下问题：

flutter type 'Timestamp' is not a subtype of type 'DateTime'

我们希望从 Cloud Firestore 获取这些用户数据：

出生 [日期时间] 性别 [字符串] 许可证 [日期时间] 名称[字符串] 大小 [字符串] 重量 [字符串]

只有 birth 和 license 作为 [Timestamp] 存储在 Cloud Firestore 中，因此我们将这些数据解析为 [DateTime]。

这是我们获取用户数据的代码：

import 'package:cloud_firestore/cloud_firestore.dart';

class User
  final String _name;
  final String _gender; // 'homme' or 'femme' or 'autre'
  final DateTime _birth;
  final DateTime _license;
  final double _weight;
  final int _size;
  DocumentReference ref;

  User(this._birth,this._gender,this._license,this._name,this._size,this._weight,this.ref);

  User.fromMap(Map<String, dynamic> map, this.ref)
      : assert(map['name'] != null && map['gender'] != null && map['birth'] != null && map['weight'] != null && map['size'] != null),
        _name = map['name'],
        _gender = map['gender'],
        _birth = map['birth'] as DateTime,
        _license = map['license'] as DateTime,
        _weight = double.parse(map['weight']),
        _size = int.parse(map['size']);

  User.fromSnapshot(DocumentSnapshot snapshot)
      : this.fromMap(snapshot.data, ref: snapshot.reference);

  String get name => _name;
  String get gender => _gender;
  DateTime get birth => _birth;
  DateTime get license => _license;
  double get weight => _weight;
  int get size => _size;

这是我们调用这些函数的地方以及问题似乎出现的地方：

import 'package:bappsalcolit/pages/homepage.dart';
import 'package:flutter/material.dart';
import 'package:bappsalcolit/sign_in/auth.dart';
import 'package:bappsalcolit/sign_in/log_page.dart';
import 'package:bappsalcolit/ads_display.dart';
import 'package:bappsalcolit/dbase/model/global_info.dart';

import 'package:cloud_firestore/cloud_firestore.dart';

User currentUser = User(null, null, null, null, null, null, null);

class RootPage extends StatefulWidget 
  RootPage(this.auth);

  final AuthImpl auth;

  @override
  State<StatefulWidget> createState() => new _RootPageState();


enum AuthStatus 
  NOT_DETERMINED,
  NOT_SIGNED_IN,
  SIGNED_IN,


class _RootPageState extends State<RootPage> 
  AuthStatus authStatus = AuthStatus.NOT_DETERMINED;
  String _userID = "";

  @override
  void initState()
    super.initState();
    Ads.hideBanner();
    widget.auth.getCurrentUser().then((user) 
      setState(() 
        if(user != null) 
          _userID = user?.uid;
        
        authStatus =
        user?.uid == null ? AuthStatus.NOT_SIGNED_IN : AuthStatus.SIGNED_IN;
      );
    );
  

  void _signedIn() 
    widget.auth.getCurrentUser().then((user)
      setState(() 
        _userID = user?.uid.toString();
      );
    );
    setState(() 
      authStatus = AuthStatus.SIGNED_IN;
    );
  

  void _signedOut() 
    setState(() 
      authStatus = AuthStatus.NOT_SIGNED_IN;
      _userID = "";
    );
  

  Widget _buildWaitingScreen() 
    return Scaffold(
      body: Container(
        height: 20.0,
        width: 20.0,
        alignment: Alignment.center,
        child: CircularProgressIndicator(),
      ),
    );
  

  //========== Here's where the problem seems to appear ==========\\
  gettingSnapshots()
    Firestore db = Firestore.instance;
    DocumentSnapshot userDS;
    db.collection('users').document(_userID).snapshots().listen((ds) async
      if (ds.exists) 
        userDS = await db.collection('users').document(_userID).get();
        try 
          currentUser = User.fromSnapshot(userDS);
         catch (e) 
          print('Error 1131: $e');
        
      
    );
  

  @override
  Widget build(BuildContext context) 
    switch (authStatus) 
      case AuthStatus.NOT_SIGNED_IN:
        return new SignIn(
          auth: widget.auth,
          onSignedIn: _signedIn,
        );
        break;
      case AuthStatus.SIGNED_IN:
        if(_userID.length > 0 && _userID != null) 
          gettingSnapshots();
          return new HomePage(
            userID: _userID,
            auth: widget.auth,
            onSignedOut: _signedOut,
          );
        
        break;
      case AuthStatus.NOT_DETERMINED:
        return _buildWaitingScreen();
        break;
    
    return _buildWaitingScreen();
  

此问题仅发生在 ios 上。在 android 上一切正常。

问题不应该来自 Cloud Firestore 和应用程序之间的链接，因为我们可以获取其他存储的信息。

【参考方案1】：

在我使用的项目中

birth: parsedJson['birth'].toDate()

而且效果很好，这是另一种选择。

【参考方案2】：

我们解决了这个问题。

我们没有对接收到的值采取行动，而是将我们的 [DateTime] 值存储为解析为 [String]。所以我们将这些参数解析回 [DateTime] 与上面描述的相同：

import 'package:cloud_firestore/cloud_firestore.dart';

class User
  final String _name;
  final String _gender; // 'homme' or 'femme' or 'autre'
  final DateTime _birth;
  final DateTime _license;
  final double _weight;
  final int _size;
  DocumentReference ref;

  User(this._birth,this._gender,this._license,this._name,this._size,this._weight,this.ref);

  User.fromMap(Map<String, dynamic> map, this.ref)
      : assert(map['name'] != null && map['gender'] != null && map['birth'] != null && map['weight'] != null && map['size'] != null),
        _name = map['name'],
        _gender = map['gender'],
        _birth = map['birth'] as DateTime,
        _license = map['license'] as DateTime,
        _weight = double.parse(map['weight']),
        _size = int.parse(map['size']);

  User.fromSnapshot(DocumentSnapshot snapshot)
      : this.fromMap(snapshot.data, ref: snapshot.reference);

  String get name => _name;
  String get gender => _gender;
  DateTime get birth => _birth;
  DateTime get license => _license;
  double get weight => _weight;
  int get size => _size;

这样问题就解决了。应该很高兴知道为什么以前的存储方式不好。

【讨论】：

编辑：这里描述了另一种解决问题的方法：***.com/questions/52996707/…

【参考方案3】：

我是新来的，不知何故我对上面的答案有一个心理障碍。

但是，我发现这对我有用。

import 'package:cloud_firestore/cloud_firestore.dart';

class User
  final String _name;
  final String _gender; // 'homme' or 'femme' or 'autre'
  final DateTime _birth;
  final DateTime _license;
  final double _weight;
  final int _size;
  DocumentReference ref;

  User(this._birth,this._gender,this._license,this._name,this._size,this._weight,this.ref);

  User.fromMap(Map<String, dynamic> map, this.ref)
      : assert(map['name'] != null && map['gender'] != null && map['birth'] != null && map['weight'] != null && map['size'] != null),
        _name = map['name'],
        _gender = map['gender'],
        _birth = (map['birth'] as Timestamp).toDate(),
        _license =(map['license'] as Timestamp).toDate(),
        _weight = double.parse(map['weight']),
        _size = int.parse(map['size']);

  User.fromSnapshot(DocumentSnapshot snapshot)
      : this.fromMap(snapshot.data, ref: snapshot.reference);

  String get name => _name;
  String get gender => _gender;
  DateTime get birth => _birth;
  DateTime get license => _license;
  double get weight => _weight;
  int get size => _size;