如何解决I / flutter9637：NoSuchMethodError：在null上调用了吸气剂“长度”
我试图解决它。但是我遇到这个问题特别针对特定用户。某些用户的数据正确显示，但某些数据给出此错误。我不明白问题出在哪里。
这是屏幕代码
FutureBuilder(
future: user.fetchData(),builder: (context,snapshot) {
if (snapshot.hasData) {
return quickInfo(snapshot.data);
} else if (snapshot.hasError) {
print(snapshot.error);
return Text("Something Error. Try again later");
}
return Container(
height: 50,alignment: Alignment.center,child: Text("Loading..."),);
},),quickInfo方法代码
Widget quickInfo(User user) {
var todayVisits = visitByDay(user);
var monthlyVisits = visitByMonth(user);
return Container(
child: Column(
children: <Widget>[
SizedBox(height: 15),Row(
mainAxisAlignment: MainAxisAlignment.spaceAround,children: <Widget>[
Column(
children: <Widget>[
Text(
todayVisits.toString() ?? '0',style: TextStyle(fontSize: 22,fontWeight: FontWeight.bold),Text("Today Visits"),],Column(
children: <Widget>[
Text(
monthlyVisits.toString() ?? '0',Text("Monthly Visits"),Column(
children: <Widget>[
Text(
user.clients.length.toString() ?? '0',Text("Total Clients"),Divider(
height: 30,thickness: 2.0,);
}
Rest API数据样本
{
"id": 1,"name": "Shibaji Debnath","mobile": "8981009499","sms_token": null,"mobile_verified_at": null,"email": "shibaji@gmail.com","email_token": null,"email_verified_at": null,"password": "$2y$10$HVZGCGnmLdluKx.nBBUKseP.3SYwb/t8.9C4aoH9ckibJRSjWr23W","remember_token": null,"avatar": null,"address": "Dum Dum","city": "Kolkata","state": "West Bengal","country": "India","pincode": 700074,"location_id": 1,"travelled": "Dum Dum","adharcard": "345678","pancard": "345678","specialisation": "0","services": null,"min_charge": "500","max_charge": "1000","online_charge": null,"qualification": "MCOM","experience": "All","language": null,"active": "0","varify": "1","payment_mode": null,"created_at": "2020-08-11T08:21:31.000000Z","updated_at": "2020-08-27T16:13:58.000000Z","rating": "2.7","clients": [
{
"id": 40,"client_id": 1,"perpose": "Astrology","details": "Know my Future","when": "2020-08-22 16:00","accepted_by": 1,"email": "imshibaji@gmail.com","org_name": "Personal","address": "12/2 Kobi Madam Mitra Lane","pincode": "700087","latitude": null,"longitude": null,"client_ip": null,"device": null,"created_at": "2020-08-19T08:30:05.000000Z","updated_at": "2020-09-01T19:13:36.000000Z"
},{
"id": 47,"client_id": 30,"perpose": "Pooja","details": "Laxmi Narayana Puja","when": "2020-08-29 14:00","name": "Bimal Roy","mobile": "6458998590","email": "bimal@abc.com","org_name": "My House","address": "Kumarpara,Dum Dum Cant. Gorabazar.","pincode": "700028","created_at": "2020-08-26T08:17:47.000000Z","updated_at": "2020-09-01T19:13:25.000000Z"
},{
"id": 48,"client_id": 31,"perpose": "Nadi","details": "Nahhii hhj","when": "2020-09-02 20:01","name": "Shyam Ghose","mobile": "6787998780","email": "shyam@abc.com","org_name": "House Party","address": "Desmukh Part","pincode": "700089","created_at": "2020-08-26T15:06:43.000000Z","updated_at": "2020-09-01T19:13:22.000000Z"
}
],"visits": [
{
"id": 1,"pandit_activity_id": 7,"pandit_id": 1,"checkIn": "2020-08-24 02:10:18","checkOut": null,"created_at": "2020-08-23T20:40:18.000000Z","updated_at": "2020-08-23T20:40:18.000000Z"
},{
"id": 2,"checkIn": "2020-08-24 02:12:40","created_at": "2020-08-23T20:42:40.000000Z","updated_at": "2020-08-23T20:42:40.000000Z"
},{
"id": 3,"checkIn": null,"checkOut": "2020-08-24 02:12:58","created_at": "2020-08-23T20:42:58.000000Z","updated_at": "2020-08-23T20:42:58.000000Z"
},{
"id": 4,"pandit_activity_id": 2,"checkIn": "2020-08-24 02:21:56","created_at": "2020-08-23T20:51:56.000000Z","updated_at": "2020-08-23T20:51:56.000000Z"
},{
"id": 5,"checkOut": "2020-08-24 02:22:00","created_at": "2020-08-23T20:52:00.000000Z","updated_at": "2020-08-23T20:52:00.000000Z"
},{
"id": 6,"pandit_activity_id": 5,"checkIn": "2020-08-24 02:22:27","created_at": "2020-08-23T20:52:27.000000Z","updated_at": "2020-08-23T20:52:27.000000Z"
},{
"id": 7,"checkOut": "2020-08-24 02:22:30","created_at": "2020-08-23T20:52:30.000000Z","updated_at": "2020-08-23T20:52:30.000000Z"
},{
"id": 8,"pandit_activity_id": 3,"checkIn": "2020-08-24 02:23:19","created_at": "2020-08-23T20:53:19.000000Z","updated_at": "2020-08-23T20:53:19.000000Z"
},{
"id": 9,"checkOut": "2020-08-24 02:23:27","created_at": "2020-08-23T20:53:27.000000Z","updated_at": "2020-08-23T20:53:27.000000Z"
},{
"id": 10,"checkIn": "2020-08-24 15:08:02","created_at": "2020-08-24T09:38:02.000000Z","updated_at": "2020-08-24T09:38:02.000000Z"
},{
"id": 11,"checkOut": "2020-08-24 15:08:06","created_at": "2020-08-24T09:38:06.000000Z","updated_at": "2020-08-24T09:38:06.000000Z"
},{
"id": 12,"pandit_activity_id": 8,"checkIn": "2020-08-24 22:27:05","created_at": "2020-08-24T16:57:05.000000Z","updated_at": "2020-08-24T16:57:05.000000Z"
},{
"id": 13,"checkOut": "2020-08-24 22:27:09","created_at": "2020-08-24T16:57:09.000000Z","updated_at": "2020-08-24T16:57:09.000000Z"
},{
"id": 14,"checkIn": "2020-08-24 22:27:37","created_at": "2020-08-24T16:57:37.000000Z","updated_at": "2020-08-24T16:57:37.000000Z"
},{
"id": 15,"checkOut": "2020-08-24 22:27:43","created_at": "2020-08-24T16:57:43.000000Z","updated_at": "2020-08-24T16:57:43.000000Z"
},{
"id": 16,"checkIn": "2020-08-24 22:36:47","created_at": "2020-08-24T17:06:47.000000Z","updated_at": "2020-08-24T17:06:47.000000Z"
},{
"id": 17,"checkOut": "2020-08-24 22:36:51","created_at": "2020-08-24T17:06:51.000000Z","updated_at": "2020-08-24T17:06:51.000000Z"
},{
"id": 18,"pandit_activity_id": 4,"checkIn": "2020-08-26 14:31:12","created_at": "2020-08-26T09:01:12.000000Z","updated_at": "2020-08-26T09:01:12.000000Z"
},{
"id": 19,"checkOut": "2020-08-26 14:32:04","created_at": "2020-08-26T09:02:04.000000Z","updated_at": "2020-08-26T09:02:04.000000Z"
},{
"id": 20,"pandit_activity_id": 6,"checkIn": "2020-08-26 14:32:21","created_at": "2020-08-26T09:02:21.000000Z","updated_at": "2020-08-26T09:02:21.000000Z"
},{
"id": 21,"checkOut": "2020-08-26 15:14:01","created_at": "2020-08-26T09:44:01.000000Z","updated_at": "2020-08-26T09:44:01.000000Z"
},{
"id": 22,"pandit_activity_id": 14,"checkOut": "2020-08-26 15:25:46","created_at": "2020-08-26T09:55:46.000000Z","updated_at": "2020-08-26T09:55:46.000000Z"
},{
"id": 23,"checkIn": "2020-08-26 16:04:40","created_at": "2020-08-26T10:34:40.000000Z","updated_at": "2020-08-26T10:34:40.000000Z"
},{
"id": 24,"checkOut": "2020-08-26 16:04:58","created_at": "2020-08-26T10:34:58.000000Z","updated_at": "2020-08-26T10:34:58.000000Z"
},{
"id": 25,"checkIn": "2020-08-26 16:06:17","created_at": "2020-08-26T10:36:17.000000Z","updated_at": "2020-08-26T10:36:17.000000Z"
},{
"id": 26,"checkOut": "2020-08-26 16:06:31","created_at": "2020-08-26T10:36:31.000000Z","updated_at": "2020-08-26T10:36:31.000000Z"
},{
"id": 27,"checkIn": "2020-08-26 16:07:04","created_at": "2020-08-26T10:37:04.000000Z","updated_at": "2020-08-26T10:37:04.000000Z"
},{
"id": 28,"checkOut": "2020-08-26 16:07:14","created_at": "2020-08-26T10:37:14.000000Z","updated_at": "2020-08-26T10:37:14.000000Z"
},{
"id": 29,"checkIn": "2020-08-26 16:08:29","created_at": "2020-08-26T10:38:29.000000Z","updated_at": "2020-08-26T10:38:29.000000Z"
},{
"id": 30,"checkOut": "2020-08-26 16:08:37","created_at": "2020-08-26T10:38:37.000000Z","updated_at": "2020-08-26T10:38:37.000000Z"
},{
"id": 31,"checkIn": "2020-08-26 16:53:51","created_at": "2020-08-26T11:23:51.000000Z","updated_at": "2020-08-26T11:23:51.000000Z"
},{
"id": 32,"checkOut": "2020-08-26 16:54:22","created_at": "2020-08-26T11:24:22.000000Z","updated_at": "2020-08-26T11:24:22.000000Z"
},{
"id": 33,"pandit_activity_id": 15,"checkOut": "2020-08-26 20:54:17","created_at": "2020-08-26T15:24:17.000000Z","updated_at": "2020-08-26T15:24:17.000000Z"
},{
"id": 34,"checkIn": "2020-08-26 20:54:31","created_at": "2020-08-26T15:24:31.000000Z","updated_at": "2020-08-26T15:24:31.000000Z"
},{
"id": 35,"checkOut": "2020-08-26 20:54:53","created_at": "2020-08-26T15:24:53.000000Z","updated_at": "2020-08-26T15:24:53.000000Z"
},{
"id": 36,"checkIn": "2020-08-26 20:55:03","created_at": "2020-08-26T15:25:03.000000Z","updated_at": "2020-08-26T15:25:03.000000Z"
},{
"id": 37,"checkIn": "2020-08-26 21:41:51","created_at": "2020-08-26T16:11:51.000000Z","updated_at": "2020-08-26T16:11:51.000000Z"
},{
"id": 38,"checkOut": "2020-08-26 21:44:37","created_at": "2020-08-26T16:14:37.000000Z","updated_at": "2020-08-26T16:14:37.000000Z"
},{
"id": 39,"pandit_activity_id": 16,"checkIn": "2020-08-26 21:44:59","created_at": "2020-08-26T16:14:59.000000Z","updated_at": "2020-08-26T16:14:59.000000Z"
},{
"id": 40,"checkOut": "2020-08-26 21:45:03","created_at": "2020-08-26T16:15:03.000000Z","updated_at": "2020-08-26T16:15:03.000000Z"
},{
"id": 41,"checkIn": "2020-08-27 01:12:45","created_at": "2020-08-26T19:42:45.000000Z","updated_at": "2020-08-26T19:42:45.000000Z"
},{
"id": 42,"checkOut": "2020-08-27 01:12:48","created_at": "2020-08-26T19:42:48.000000Z","updated_at": "2020-08-26T19:42:48.000000Z"
},{
"id": 45,"checkIn": "2020-08-31 14:48:36","created_at": "2020-08-31T09:18:36.000000Z","updated_at": "2020-08-31T09:18:36.000000Z"
},{
"id": 46,"checkOut": "2020-08-31 14:51:22","created_at": "2020-08-31T09:21:22.000000Z","updated_at": "2020-08-31T09:21:22.000000Z"
},"checkIn": "2020-08-31 14:51:39","created_at": "2020-08-31T09:21:39.000000Z","updated_at": "2020-08-31T09:21:39.000000Z"
}
],"payments": [
]
}
User.dart
import 'dart:convert';
import 'package:PandeetApp/services/activity.dart';
class User {
int id;
String name;
String mobile;
String smsToken;
String mobileVerifiedAt;
String email;
String emailToken;
Null emailVerifiedAt;
String password;
String rememberToken;
String avatar;
String address;
String city;
String state;
String country;
int pincode;
int locationId;
String travelled;
String adharcard;
String pancard;
String specialisation;
List services;
String minCharge;
String maxCharge;
String onlineCharge;
String qualification;
String experience;
String language;
String active;
String varify;
PaymentMode paymentMode;
String createdAt;
String updatedAt;
String rating;
List<Clients> clients;
List<Visits> visits;
List<Payments> payments;
User({
this.id,this.name,this.mobile,this.smsToken,this.mobileVerifiedAt,this.email,this.emailToken,this.emailVerifiedAt,this.password,this.rememberToken,this.avatar,this.address,this.city,this.state,this.country,this.pincode,this.locationId,this.travelled,this.adharcard,this.pancard,this.specialisation,this.services,this.minCharge,this.maxCharge,this.onlineCharge,this.qualification,this.experience,this.language,this.active,this.varify,this.paymentMode,this.createdAt,this.updatedAt,this.rating,this.clients,this.visits,this.payments,});
Future<User> fetchData() async {
var data = await PanditActivity().profile();
// print(data);
return new User.fromJson(data);
}
User.fromJson(Map<String,dynamic> json) {
id = json['id'];
name = json['name'];
mobile = json['mobile'];
smsToken = json['sms_token'];
mobileVerifiedAt = json['mobile_verified_at'];
email = json['email'];
emailToken = json['email_token'];
emailVerifiedAt = json['email_verified_at'];
password = json['password'];
rememberToken = json['remember_token'];
avatar = json['avatar'];
address = json['address'];
city = json['city'];
state = json['state'];
country = json['country'];
pincode = json['pincode'];
locationId = json['location_id'];
travelled = json['travelled'];
adharcard = json['adharcard'];
pancard = json['pancard'];
specialisation = json['specialisation'];
services = jsonDecode(json['services']) ?? [];
minCharge = json['min_charge'];
maxCharge = json['max_charge'];
onlineCharge = json['online_charge'];
qualification = json['qualification'];
experience = json['experience'];
language = json['language'];
active = json['active'];
varify = json['varify'];
paymentMode = json['payment_mode'] != null
? new PaymentMode.fromJson(jsonDecode(json['payment_mode']))
: PaymentMode();
createdAt = json['created_at'];
updatedAt = json['updated_at'];
rating = json['rating'];
if (json['clients'] != null) {
clients = new List<Clients>();
json['clients'].forEach((v) {
clients.add(new Clients.fromJson(v));
});
}
if (json['visits'] != null) {
visits = new List<Visits>();
json['visits'].forEach((v) {
visits.add(new Visits.fromJson(v));
});
}
if (json['payments'] != null) {
payments = new List<Payments>();
json['payments'].forEach((v) {
payments.add(new Payments.fromJson(v));
});
}
}
Map<String,String> toJson() {
final Map<String,String> data = new Map<String,String>();
data['id'] = this.id.toString();
data['name'] = this.name;
data['mobile'] = this.mobile;
data['sms_token'] = this.smsToken;
data['mobile_verified_at'] = this.mobileVerifiedAt;
data['email'] = this.email;
data['email_token'] = this.emailToken;
data['email_verified_at'] = this.emailVerifiedAt;
data['password'] = this.password;
data['remember_token'] = this.rememberToken;
data['avatar'] = this.avatar;
data['address'] = this.address;
data['city'] = this.city;
data['state'] = this.state;
data['country'] = this.country;
data['pincode'] = this.pincode.toString();
data['location_id'] = this.locationId.toString();
data['travelled'] = this.travelled;
data['adharcard'] = this.adharcard;
data['pancard'] = this.pancard;
data['specialisation'] = this.specialisation;
data['services'] = jsonEncode(this.services);
data['min_charge'] = this.minCharge;
data['max_charge'] = this.maxCharge;
data['online_charge'] = this.onlineCharge;
data['qualification'] = this.qualification;
data['experience'] = this.experience;
data['language'] = this.language;
data['active'] = this.active;
data['varify'] = this.varify;
if (this.paymentMode != null) {
data['payment_mode'] = jsonEncode(this.paymentMode.toJson());
}
data['created_at'] = this.createdAt;
data['updated_at'] = this.updatedAt;
data['rating'] = this.rating;
if (this.clients != null) {
data['clients'] = this.clients.map((v) => v.toJson()).toList().toString();
}
if (this.visits != null) {
data['visits'] = this.visits.map((v) => v.toJson()).toList().toString();
}
if (this.payments != null) {
data['payments'] =
this.payments.map((v) => v.toJson()).toList().toString();
}
return data;
}
}
class PaymentMode {
String bankName;
String bankAddress;
String ifscCode;
String accountNo;
String accountHolder;
PaymentMode(
{this.bankName,this.ifscCode,this.accountNo,this.accountHolder});
PaymentMode.fromJson(Map<String,dynamic> json) {
bankName = json['bank_name'];
bankAddress = json['bank_address'];
ifscCode = json['ifsc_code'];
accountNo = json['account_no'];
accountHolder = json['account_holder'];
}
Map<String,String>();
data['bank_name'] = this.bankName;
data['bank_address'] = this.bankAddress;
data['ifsc_code'] = this.ifscCode;
data['account_no'] = this.accountNo;
data['account_holder'] = this.accountHolder;
return data;
}
}
class Clients {
int id;
int clientId;
String perpose;
String details;
String when;
int acceptedBy;
String name;
String mobile;
String email;
String orgName;
String address;
String city;
String state;
String pincode;
String country;
String latitude;
String longitude;
String clientIp;
String device;
String createdAt;
String updatedAt;
Clients(
{this.id,this.clientId,this.perpose,this.details,this.when,this.acceptedBy,this.orgName,this.latitude,this.longitude,this.clientIp,this.device,this.updatedAt});
Clients.fromJson(Map<String,dynamic> json) {
id = json['id'];
clientId = json['client_id'];
perpose = json['perpose'];
details = json['details'];
when = json['when'];
acceptedBy = json['accepted_by'];
name = json['name'];
mobile = json['mobile'];
email = json['email'];
orgName = json['org_name'];
address = json['address'];
city = json['city'];
state = json['state'];
pincode = json['pincode'];
country = json['country'];
latitude = json['latitude'];
longitude = json['longitude'];
clientIp = json['client_ip'];
device = json['device'];
createdAt = json['created_at'];
updatedAt = json['updated_at'];
}
Map<String,String>();
data['id'] = this.id.toString();
data['client_id'] = this.clientId.toString();
data['perpose'] = this.perpose;
data['details'] = this.details;
data['when'] = this.when;
data['accepted_by'] = this.acceptedBy.toString();
data['name'] = this.name;
data['mobile'] = this.mobile;
data['email'] = this.email;
data['org_name'] = this.orgName;
data['address'] = this.address;
data['city'] = this.city;
data['state'] = this.state;
data['pincode'] = this.pincode;
data['country'] = this.country;
data['latitude'] = this.latitude;
data['longitude'] = this.longitude;
data['client_ip'] = this.clientIp;
data['device'] = this.device;
data['created_at'] = this.createdAt;
data['updated_at'] = this.updatedAt;
return data;
}
}
class Visits {
int id;
int panditActivityId;
int panditId;
String checkIn;
String checkOut;
String createdAt;
String updatedAt;
Visits(
{this.id,this.panditActivityId,this.panditId,this.checkIn,this.checkOut,this.updatedAt});
Visits.fromJson(Map<String,dynamic> json) {
id = json['id'];
panditActivityId = json['pandit_activity_id'];
panditId = json['pandit_id'];
checkIn = json['checkIn'];
checkOut = json['checkOut'];
createdAt = json['created_at'];
updatedAt = json['updated_at'];
}
Map<String,String>();
data['id'] = this.id.toString();
data['pandit_activity_id'] = this.panditActivityId.toString();
data['pandit_id'] = this.panditId.toString();
data['checkIn'] = this.checkIn;
data['checkOut'] = this.checkOut;
data['created_at'] = this.createdAt;
data['updated_at'] = this.updatedAt;
return data;
}
}
class Payments {
int id;
int panditId;
String details;
String mode;
String creditAmt;
String debitAmt;
String createdAt;
String updatedAt;
Payments(
{this.id,this.mode,this.creditAmt,this.debitAmt,this.updatedAt});
Payments.fromJson(Map<String,dynamic> json) {
id = json['id'];
panditId = json['pandit_id'];
details = json['details'];
mode = json['mode'];
creditAmt = json['credit_amt'].toString();
debitAmt = json['debit_amt'].toString();
createdAt = json['created_at'];
updatedAt = json['updated_at'];
}
Map<String,String>();
data['id'] = this.id.toString();
data['pandit_id'] = this.panditId.toString();
data['details'] = this.details;
data['mode'] = this.mode;
data['credit_amt'] = this.creditAmt;
data['debit_amt'] = this.debitAmt;
data['created_at'] = this.createdAt;
data['updated_at'] = this.updatedAt;
return data;
}
}
我认为可能是来自user.dart的问题。但是我不明白，问题出在哪里。谢谢大家。
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