您好，我正在尝试使用条形码扫描仪扫描个人的记录。条形码带来的结果就是该个人的ID。因此，我将ID附加到一个链接，该链接会将我带到该人员的详细信息页面，我可以在其中查看详细信息，但是在扫描后立即出现此错误。
NoSuchMethodError: the getter 'firstName' was called on null. Receiver: null.
这是我第一个关于扑动的项目，我需要帮助。
这是我的条形码扫描屏幕：
import 'dart:async';
import 'package:erg_app/ProfilePage.dart';
import 'package:erg_app/Anchors.dart';
import 'package:flutter/material.dart';
import 'package:flutter/widgets.dart';
import 'package:barcode_scan/barcode_scan.dart';
import 'package:erg_app/Animations/FadeAnimation.dart';
import 'package:flutter/services.dart';
void main() {
runApp(MaterialApp(
debugShowCheckedModeBanner: false,
home: StartScanPage(),
));
}
class StartScanPage extends StatefulWidget {
@override
StartScanPageState createState() {
return new StartScanPageState();
}
}
class StartScanPageState extends State<StartScanPage> {
String result = "Bio Data:";
Future _scanQR() async {
try {
String qrResult = await BarcodeScanner.scan();
print(qrResult);
Navigator.of(context).push(
MaterialPageRoute(
builder: (context) => ProfilePage(result: qrResult),
),
);
// setState(() {
// result = qrResult;
// });
} on PlatformException catch (ex) {
if (ex.code == BarcodeScanner.CameraAccessDenied) {
setState(() {
result = "Camera permission was denied";
});
} else {
setState(() {
result = "Unknown Error $ex";
});
}
} on FormatException {
setState(() {
result = "You pressed the back button before scanning anything";
});
} catch (ex) {
setState(() {
result = "Unknown Error $ex";
});
}
}
@override
Widget build(BuildContext context) {
return Scaffold(
body: SafeArea(
child: Container(
width: double.infinity,
height: MediaQuery.of(context).size.height,
padding: EdgeInsets.symmetric(horizontal: 30, vertical: 50),
child: Column(
mainAxisAlignment: MainAxisAlignment.spaceBetween,
crossAxisAlignment: CrossAxisAlignment.center,
children: <Widget>[
Column(
children: <Widget>[
FadeAnimation(
1,
Text(
"Verify Farmer",
style: TextStyle(
fontWeight: FontWeight.bold, fontSize: 30),
)),
SizedBox(
height: 20,
),
FadeAnimation(
1.2,
Text(
"Automatic identity verification which enables you to verify each farmer applicant",
textAlign: TextAlign.center,
style: TextStyle(color: Colors.grey[700], fontSize: 15),
)),
],
),
FadeAnimation(
1.4,
Container(
height: MediaQuery.of(context).size.height / 3,
decoration: BoxDecoration(
image: DecorationImage(
image:
AssetImage('assets/images/illustration1.png'))),
)),
Column(
children: <Widget>[
FadeAnimation(
1.5,
MaterialButton(
color: Colors.green,
minWidth: double.infinity,
height: 60,
onPressed: _scanQR,
shape: RoundedRectangleBorder(
side: BorderSide(color: Colors.green),
borderRadius: BorderRadius.circular(50)),
child: Text(
"Start Scan",
style: TextStyle(
color: Colors.white,
fontWeight: FontWeight.w600,
fontSize: 18),
),
)),
SizedBox(
height: 20,
),
FadeAnimation(
1.6,
Container(
// padding: EdgeInsets.only(top: 3, left: 3),
decoration: BoxDecoration(
borderRadius: BorderRadius.circular(50),
border: Border(
bottom: BorderSide(color: Colors.green),
top: BorderSide(color: Colors.green),
left: BorderSide(color: Colors.green),
right: BorderSide(color: Colors.green),
)),
child: MaterialButton(
minWidth: double.infinity,
height: 60,
onPressed: () {
Navigator.push(
context,
MaterialPageRoute(
builder: (context) => AnchorsPage()));
},
color: Colors.white,
elevation: 0,
shape: RoundedRectangleBorder(
borderRadius: BorderRadius.circular(50)),
child: Text(
"Cancel",
style: TextStyle(
// color: Colors.white,
fontWeight: FontWeight.w600,
fontSize: 18),
),
),
))
],
)
],
),
),
),
);
}
}
这是“用户详细信息”屏幕
import 'package:erg_app/StartScan.dart';
import 'package:flutter/material.dart';
import 'package:get_it/get_it.dart';
import 'package:erg_app/models/farmer_model.dart';
import 'package:erg_app/api/farmers_services.dart';
class ProfilePage extends StatefulWidget {
final String result;
ProfilePage({this.result});
@override
_ProfilePageState createState() => _ProfilePageState();
}
class _ProfilePageState extends State<ProfilePage> {
FarmersService get fromersService => GetIt.I<FarmersService>();
String errorMessage;
FarmerClass farmer;
@override
void initState() {
fromersService.getFarmer(widget.result)
.then((response) {
if (response.error) {
errorMessage = response.errorMessage ?? 'An error occurred';
}
farmer = response.data;
});
}
@override
Widget build(BuildContext context) {
// TODO: implement build
return MaterialApp(
debugShowCheckedModeBanner: false,
home: Scaffold(
appBar: AppBar(
title: new Center(
child: new Text('Farmers Data', textAlign: TextAlign.left)),
iconTheme: IconThemeData(color: Colors.white),
backgroundColor: Colors.green,
leading: new IconButton(
icon: new Icon(Icons.assignment_ind),
onPressed: () {},
),
),
// backgroundColor: Colors.green[50],
body: Container(
child: ListView(
children: <Widget>[
Container(
margin: EdgeInsets.only(top: 20),
),
CircleAvatar(
radius: 80,
backgroundColor: Colors.grey,
// backgroundImage: AssetImage('assets/images/user.png'),
),
Text(
farmer.firstName ?? 'An error occurred',
style: TextStyle(
fontFamily: 'SourceSansPro',
fontSize: 25,
),
textAlign: TextAlign.center,
),
Text(
'Welcome',
style: TextStyle(
fontSize: 20,
fontFamily: 'SourceSansPro',
color: Colors.green[400],
letterSpacing: 2.5,
),
textAlign: TextAlign.center,
),
Container(
margin: EdgeInsets.only(top: 20),
),
SizedBox(
height: 20.0,
width: 200,
child: Divider(
color: Colors.teal[100],
),
),
Text(
'Farmer Details',
textAlign: TextAlign.center,
),
Card(
color: Colors.white,
margin: EdgeInsets.symmetric(vertical: 10.0, horizontal: 25.0),
child: ListTile(
leading: Text(
'BVN:',
style: TextStyle(
fontSize: 20,
fontFamily: 'SourceSansPro',
color: Colors.green[700],
letterSpacing: 2.5,
),
),
title: Text(
farmer.bvn ,
style: TextStyle(fontFamily: 'BalooBhai', fontSize: 20.0),
),
),
),
Card(
color: Colors.white,
margin: EdgeInsets.symmetric(vertical: 10.0, horizontal: 25.0),
child: ListTile(
leading: Text(
'ID:',
style: TextStyle(
fontSize: 20,
fontFamily: 'SourceSansPro',
color: Colors.green[700],
letterSpacing: 2.5,
),
),
title: Text(
farmer.applicationId,
style: TextStyle(fontFamily: 'BalooBhai', fontSize: 20.0),
),
),
),
Card(
color: Colors.white,
margin: EdgeInsets.symmetric(vertical: 10.0, horizontal: 25.0),
child: ListTile(
leading: Text(
'Appicant ID:'?? 'An error occurred',
style: TextStyle(
fontSize: 20,
fontFamily: 'SourceSansPro',
color: Colors.green[700],
letterSpacing: 2.5,
),
),
title: Text(
"p.appliId",
style: TextStyle(fontFamily: 'BalooBhai', fontSize: 20.0),
),
),
),
Card(
color: Colors.white,
margin: EdgeInsets.symmetric(vertical: 10.0, horizontal: 25.0),
child: ListTile(
leading: Text(
'State/LGA:',
style: TextStyle(
fontSize: 20,
fontFamily: 'SourceSansPro',
color: Colors.green[700],
letterSpacing: 2.5,
),
),
title: Text(
"p.state",
style: TextStyle(fontFamily: 'BalooBhai', fontSize: 20.0),
),
),
),
Card(
color: Colors.white,
margin: EdgeInsets.symmetric(vertical: 10.0, horizontal: 25.0),
child: ListTile(
leading: Text(
'Farm Size:',
style: TextStyle(
fontSize: 20,
fontFamily: 'SourceSansPro',
color: Colors.green[700],
letterSpacing: 2.5,
),
),
title: Text(
"p.farmsize",
style: TextStyle(fontFamily: 'BalooBhai', fontSize: 20.0),
),
),
),
Card(
color: Colors.white,
margin: EdgeInsets.symmetric(vertical: 10.0, horizontal: 25.0),
child: ListTile(
leading: Text(
'Geo Coord.:',
style: TextStyle(
fontSize: 20,
fontFamily: 'SourceSansPro',
color: Colors.green[700],
letterSpacing: 2.5,
),
),
title: Text(
"p.geocord",
style: TextStyle(fontFamily: 'BalooBhai', fontSize: 20.0),
),
),
),
Divider(),
Divider(),
Container(
margin: EdgeInsets.only(top: 20, bottom: 30),
child: Center(
child: RaisedButton(
padding: EdgeInsets.fromLTRB(80, 10, 80, 10),
color: Colors.green,
child: Text(
"Complete",
style: TextStyle(
color: Colors.white,
fontWeight: FontWeight.bold,
fontSize: 14),
),
onPressed: () {
Navigator.of(context).push(MaterialPageRoute(
builder: (context) => StartScanPage()));
},
shape: RoundedRectangleBorder(
borderRadius: BorderRadius.circular(50),
),
),
),
),
],
),
),
),
);
}
}
我的http服务类：
import 'dart:convert';
import 'package:http/http.dart'
as http; // add the http plugin in pubspec.yaml file.
import 'package:erg_app/models/farmer_model.dart';
import 'package:erg_app/models/api_response.dart';
class FarmersService {
Future<APIResponse<FarmerClass>> getFarmer(String bvn) {
final queryParameters = {
'Bvn': bvn,
};
final url = new Uri.http(
'api.ergagro.com:112', '/CheckDailyStockTakingStatus', queryParameters);
return http
.get(url, headers: {'Content-Type': 'application/json'}).then((data) {
if (data.statusCode == 200) {
final jsonData = json.decode(data.body);
print('Data Received');
return APIResponse<FarmerClass>(data: FarmerClass.fromJson(jsonData));
}
return APIResponse<FarmerClass>(
error: true, errorMessage: 'An error occured');
}).catchError((_) => APIResponse<FarmerClass>(
error: true, errorMessage: 'An error occured'));
}
}
型号：
// To parse this JSON data, do
//
// final farmer = farmerFromJson(jsonString);
import 'dart:convert';
Farmer farmerFromJson(String str) => Farmer.fromJson(json.decode(str));
String farmerToJson(Farmer data) => json.encode(data.toJson());
class Farmer {
Farmer({
this.statusCode,
this.message,
this.success,
this.farmer,
});
int statusCode;
String message;
bool success;
FarmerClass farmer;
factory Farmer.fromJson(Map<String, dynamic> json) => Farmer(
statusCode: json["StatusCode"],
message: json["Message"],
success: json["Success"],
farmer: FarmerClass.fromJson(json["Farmer"]),
);
Map<String, dynamic> toJson() => {
"StatusCode": statusCode,
"Message": message,
"Success": success,
"Farmer": farmer.toJson(),
};
}
class FarmerClass {
FarmerClass({
this.oid,
this.applicationId,
this.bvn,
this.firstName,
this.middleName,
this.lastName,
this.fullName,
this.gender,
this.dateOfBirth,
this.phoneNo,
this.lga,
this.state,
this.provider,
this.anchor,
this.polygon,
this.size,
this.farmImage,
this.signature,
this.landDocument,
this.maritalStatus,
this.project,
this.nokFirstName,
this.nokSurname,
this.nokOtherName,
this.nokPhone,
this.nokBvn,
this.address,
this.spouseName,
this.spouseBvn,
this.relationship,
this.season,
this.propertySize,
this.propertyOwner,
this.photoPath,
this.anchorAcronym,
this.logoUrl,
this.bank,
this.bankLogoUrl,
this.photoUrl,
});
int oid;
String applicationId;
String bvn;
String firstName;
String middleName;
String lastName;
String fullName;
String gender;
DateTime dateOfBirth;
String phoneNo;
String lga;
String state;
String provider;
String anchor;
String polygon;
double size;
dynamic farmImage;
dynamic signature;
dynamic landDocument;
dynamic maritalStatus;
String project;
String nokFirstName;
String nokSurname;
String nokOtherName;
String nokPhone;
dynamic nokBvn;
String address;
String spouseName;
dynamic spouseBvn;
String relationship;
dynamic season;
dynamic propertySize;
String propertyOwner;
String photoPath;
String anchorAcronym;
String logoUrl;
String bank;
String bankLogoUrl;
String photoUrl;
factory FarmerClass.fromJson(Map<String, dynamic> json) => FarmerClass(
oid: json["Oid"],
applicationId: json["ApplicationId"],
bvn: json["Bvn"],
firstName: json["FirstName"],
middleName: json["MiddleName"],
lastName: json["LastName"],
fullName: json["FullName"],
gender: json["Gender"],
dateOfBirth: DateTime.parse(json["DateOfBirth"]),
phoneNo: json["PhoneNo"],
lga: json["Lga"],
state: json["State"],
provider: json["Provider"],
anchor: json["Anchor"],
polygon: json["Polygon"],
size: json["Size"].toDouble(),
farmImage: json["FarmImage"],
signature: json["Signature"],
landDocument: json["LandDocument"],
maritalStatus: json["MaritalStatus"],
project: json["Project"],
nokFirstName: json["NokFirstName"],
nokSurname: json["NokSurname"],
nokOtherName: json["NokOtherName"],
nokPhone: json["NokPhone"],
nokBvn: json["NokBvn"],
address: json["Address"],
spouseName: json["SpouseName"],
spouseBvn: json["SpouseBvn"],
relationship: json["Relationship"],
season: json["Season"],
propertySize: json["PropertySize"],
propertyOwner: json["PropertyOwner"],
photoPath: json["PhotoPath"],
anchorAcronym: json["AnchorAcronym"],
logoUrl: json["LogoUrl"],
bank: json["Bank"],
bankLogoUrl: json["BankLogoUrl"],
photoUrl: json["PhotoUrl"],
);
Map<String, dynamic> toJson() => {
"Oid": oid,
"ApplicationId": applicationId,
"Bvn": bvn,
"FirstName": firstName,
"MiddleName": middleName,
"LastName": lastName,
"FullName": fullName,
"Gender": gender,
"DateOfBirth": dateOfBirth.toIso8601String(),
"PhoneNo": phoneNo,
"Lga": lga,
"State": state,
"Provider": provider,
"Anchor": anchor,
"Polygon": polygon,
"Size": size,
"FarmImage": farmImage,
"Signature": signature,
"LandDocument": landDocument,
"MaritalStatus": maritalStatus,
"Project": project,
"NokFirstName": nokFirstName,
"NokSurname": nokSurname,
"NokOtherName": nokOtherName,
"NokPhone": nokPhone,
"NokBvn": nokBvn,
"Address": address,
"SpouseName": spouseName,
"SpouseBvn": spouseBvn,
"Relationship": relationship,
"Season": season,
"PropertySize": propertySize,
"PropertyOwner": propertyOwner,
"PhotoPath": photoPath,
"AnchorAcronym": anchorAcronym,
"LogoUrl": logoUrl,
"Bank": bank,
"BankLogoUrl": bankLogoUrl,
"PhotoUrl": photoUrl,
};
}
我的get_it类
class APIResponse<T> {
T data;
bool error;
String errorMessage;
APIResponse({this.data, this.errorMessage, this.error = false});
}
请有人帮我吗？