问题描述
我正在尝试从提供程序获取响应并在ui页面中获取，但是当我尝试向ui添加响应时，它显示错误
The getter 'data' was called on null. Receiver: null Tried calling: data
在此行：
ListView.builder(
physics: ClampingScrollPhysics(),shrinkWrap: true,itemCount: doctorList.data.length,primary: true,这是正确的方法还是需要更改模式类或ui集成。 即时消息通过doctorList.data .->数据数据访问数据。
我的响应模式类。
import 'dart:convert';
Doctorlist doctorlistFromJson(String str) => Doctorlist.fromJson(json.decode(str));
String doctorlistToJson(Doctorlist data) => json.encode(data.toJson());
class Doctorlist {
Doctorlist({
this.status,this.message,this.data,});
int status;
String message;
List<Datum> data;
factory Doctorlist.fromJson(Map<String,dynamic> json) => Doctorlist(
status: json["status"],message: json["message"],data: List<Datum>.from(json["data"].map((x) => Datum.fromJson(x))),);
Map<String,dynamic> toJson() => {
"status": status,"message": message,"data": List<dynamic>.from(data.map((x) => x.toJson())),};
}
class Datum {
Datum({
this.id,this.mobile,this.userImage,this.emrNumber,this.hospital,this.status,this.doctorName,this.docRole,this.email,this.gender,this.address,this.city,this.state,this.pincode,this.clinicName,this.appointmentDate,this.favourite,});
String id;
String mobile;
String userImage;
String emrNumber;
String hospital;
String status;
String doctorName;
String docRole;
String email;
String gender;
String address;
String city;
String state;
String pincode;
String clinicName;
DateTime appointmentDate;
String favourite;
factory Datum.fromJson(Map<String,dynamic> json) => Datum(
id: json["id"],mobile: json["mobile"],userImage: json["user_image"],no: json["no"],hospital: json["hospital"],status: json["status"],doctorName: json["doctor_name"],docRole: json["doc_role"],email: json["email"],gender: json["gender"],address: json["address"],city: json["city"],state: json["state"],pincode: json["pincode"],clinicName: json["clinic_name"],appointmentDate: DateTime.parse(json["appointment_date"]),favourite: json["favourite"],dynamic> toJson() => {
"id": id,"mobile": mobile,"user_image": userImage,"emr_number": emrNumber,"hospital": hospital,"status": status,"doctor_name": doctorName,"doc_role": docRole,"email": email,"gender": gender,"address": address,"city": city,"state": state,"pincode": pincode,"clinic_name": clinicName,"appointment_date": "${appointmentDate.year.toString().padLeft(4,'0')}-${appointmentDate.month.toString().padLeft(2,'0')}-${appointmentDate.day.toString().padLeft(2,'0')}","favourite": favourite,};
}
我的提供者类：
class DoctorListProvider extends ChangeNotifier {
Doctorlist doctorList;
Future<Doctorlist> doctorlist() async {
try {
final response = await http.post(
(Commons.baseURL + "/list"),headers: {
"Accept": "application/json","content-type": "application/json",},body:{"id":5});
if (response.statusCode == 200) {
var responseJson = Commons.returnResponse(response);
doctorList = Doctorlist.fromJson(responseJson);
print(doctorList);
return Doctorlist.fromJson(responseJson);
} else {
return null;
}
} on SocketException {
return null;
}
}
}
“我的ui列表视图”构建器页面：
class _DoctorState extends State<Doctor> {
Doctorlist doctorList;
bool fav = true;
@override
void initState() {
doctorList =
Provider.of<DoctorListProvider>(context,listen: false).doctorList;
super.initState();
}
@override
Widget build(BuildContext context) {
ListView.builder(
physics: ClampingScrollPhysics(),// itemCount: 2,// reverse: false,itemBuilder: (BuildContext context,int index) {
return Column(
mainAxisSize: MainAxisSize.min,children: <Widget>[
Container(
child: Flexible(
child:
Container(child:
InkWell(
onTap: (){
Navigator.push(context,MaterialPageRoute(builder: (context) => Doctordetails()));
},child:
Card(
// color: Color(0xff29ABE2),child: ConstrainedBox(
constraints: BoxConstraints(
minHeight: 100,),child: Padding(
padding: EdgeInsets.only(
left: 10,right: 0,top: 10),child: Row(
children: <Widget>[
Column(
crossAxisAlignment:
CrossAxisAlignment
.start,children: <Widget>[
Row(
mainAxisAlignment:
MainAxisAlignment
.start,crossAxisAlignment:
CrossAxisAlignment
.start,children: <
Widget>[
Container(
decoration:
new BoxDecoration(
borderRadius:
BorderRadius.all(
const Radius.circular(100.0)),border: Border.all(
color: Colors
.black),height: 70,width: 70,child:
ClipRRect(
borderRadius:
BorderRadius.circular(
200),child: Image
.asset(
'assets/images/registration/profile_side.png',fit: BoxFit
.fill,SizedBox(
width: MediaQuery.of(
context)
.size
.height /
80,Column(
crossAxisAlignment:
CrossAxisAlignment
.start,children: <
Widget>[
Text(
"no",style: TextStyle(
fontFamily:
"SansBold",fontSize:
15,color:
Colors.black),Text(
"no",style: TextStyle(
fontFamily:
"SansRegular",SizedBox(
height: 5,SizedBox(
height: MediaQuery.of(context)
.size
.height /
13,width: MediaQuery.of(context)
.size
.width /
1.9,child:
AutoSizeText(
'no ',style: TextStyle(
fontSize:
20),maxLines:
3,)
],Container(
child:
IconButton(
onPressed:
() {
setState(
() {
fav =
!fav;
});
},icon: fav
? Image.asset(
"assets/images/appointment/favourite_unselected.png")
: Image.asset(
"assets/images/appointment/favourite_select.png"),))
],SizedBox(
height: 5,Row(
children: <
Widget>[
Container(
child: IconButton(
icon: Image
.asset(
"assets/images/appointment/last_appointment.png"),onPressed:
null),SizedBox(
width: 10,Text(
"Last appointment date",style: TextStyle(
fontFamily:
"SansRegular",fontSize:
15,color: Colors
.black),)
],Container(
child: Text(
"06-08-2020"),],SizedBox(
width: MediaQuery.of(
context)
.size
.width /
40,))))))))
],);
},我的Json响应看起来像这样。
{
"status": 1,"message": "success","data": [
{
"id": "1","mobile": "7","user_image": "https://hghjfjd.com","emr_number": "er-357","hospital": "ff","status": "1","doctor_name": "sanje","doc_role": "dfd","email": "doctor@gmail.com","gender": "Male","address": "test mode","city": "england","state": "tn","pincode": "633211","clinic_name": "clinic","appointment_date": "2020-09-07","favourite": "No"
},解决方法
尝试一下：
）：将initState()方法编辑为：
@override
void initState(){
WidgetsBinding.instance.addPostFrameCallback((_) => _afterLayout(context));
}
）：现在，您可以使用_afterLayout(context)方法加载项目：
_afterLayout(BuildContext context) async {
var docState = Provider.of<DoctorListProvider>(context);
docState.setDoctorList(await docState.doctorlist());
}
）：更新此类DoctorListProvider：
class DoctorListProvider extends ChangeNotifier {
Doctorlist _doctorList;
Doctorlist get getDoctorList => _doctorList;
set setDoctorList(Doctorlist input){
_doctorList = input;
notifierListners();
}
...
}
）：最后在您的UI中使用它：
class _DoctorState extends State<Doctor> {
bool fav = true;
@override
void initState(){
WidgetsBinding.instance.addPostFrameCallback((_) => _afterLayout(context));
}
@override
Widget build(BuildContext context) {
var docState = Provider.of<DoctorListProvider>(context);
return docState.getDoctorList == null ? Container(child: CircularProgressIndicator()) :
ListView.builder(
physics: ClampingScrollPhysics(),shrinkWrap: true,itemCount: docState.getDoctorList.data.length,// itemCount: 2,// reverse: false,primary: true,itemBuilder: (BuildContext context,int index) {