问题
I am able to fetch the JSON data successfully, but not able to fetch the fields of JSON data and build a list in flutter.
This is the code I am using to fetch the field data
OrderModel.fromJson(Map<String, dynamic> json) {
error = json['error'];
if (json['content'] != null) {
content = new List<OrderContent>();
json['content'].forEach((v) {
content.add(new OrderContent.fromJson(v));
});
}
}
The json['content'] is Map<String, dynamic>.
In .forEach((v) what should I write to get the data? I am new to this flutter and JSON learning, I think I am wrong at this point only
THE JSON DATA STRUCTURE ON WHICH I AM WORKING IS BELOW
{
"error": "false",
"content": {
"16": [
[
{
"sod_pk": "31688",
"soh_fk": "23660",
"sqd_fk": "33294",
"order_header": {
"soh_pk": "23660",
"order_no": "16",
}
}
],
[
{
"sod_pk": "31689",
"soh_fk": "23660",
"sqd_fk": "33293",
"order_header": {
"soh_pk": "23660",
"order_no": "16",
}
}
]
],
"18": [
[
{
"sod_pk": "31744",
"soh_fk": "23702",
"sqd_fk": "33354",
"order_header": {
"soh_pk": "23702",
"order_no": "18",
}
}
],
[
{
"sod_pk": "31745",
"soh_fk": "23702",
"sqd_fk": "33356",
"order_header": {
"soh_pk": "23702",
"order_no": "18",
}
}
],
]
}
}
the above JSON data structure has the order no nested in every item details, which has to be fetched inside all order numbers, then the respective data of orders.
回答1:
You can copy paste run full code below
Step 1: You can parse with payloadFromJson, content field is Map<String, List<List<OrderContent>>>, please see full code below
Step 2: Display with FutureBuilder and ListView.separated
working demo
full code
import 'package:flutter/material.dart';
import 'package:http/http.dart' as http;
import 'dart:convert';
Payload payloadFromJson(String str) => Payload.fromJson(json.decode(str));
String payloadToJson(Payload data) => json.encode(data.toJson());
class Payload {
Payload({
this.error,
this.content,
});
String error;
Map<String, List<List<OrderContent>>> content;
factory Payload.fromJson(Map<String, dynamic> json) => Payload(
error: json["error"],
content: Map.from(json["content"]).map((k, v) =>
MapEntry<String, List<List<OrderContent>>>(
k,
List<List<OrderContent>>.from(v.map((x) =>
List<OrderContent>.from(
x.map((x) => OrderContent.fromJson(x))))))),
);
Map<String, dynamic> toJson() => {
"error": error,
"content": Map.from(content).map((k, v) => MapEntry<String, dynamic>(
k,
List<dynamic>.from(
v.map((x) => List<dynamic>.from(x.map((x) => x.toJson())))))),
};
}
class OrderContent {
OrderContent({
this.sodPk,
this.sohFk,
this.sqdFk,
this.orderHeader,
});
String sodPk;
String sohFk;
String sqdFk;
OrderHeader orderHeader;
factory OrderContent.fromJson(Map<String, dynamic> json) => OrderContent(
sodPk: json["sod_pk"],
sohFk: json["soh_fk"],
sqdFk: json["sqd_fk"],
orderHeader: OrderHeader.fromJson(json["order_header"]),
);
Map<String, dynamic> toJson() => {
"sod_pk": sodPk,
"soh_fk": sohFk,
"sqd_fk": sqdFk,
"order_header": orderHeader.toJson(),
};
}
class OrderHeader {
OrderHeader({
this.sohPk,
this.orderNo,
});
String sohPk;
String orderNo;
factory OrderHeader.fromJson(Map<String, dynamic> json) => OrderHeader(
sohPk: json["soh_pk"],
orderNo: json["order_no"],
);
Map<String, dynamic> toJson() => {
"soh_pk": sohPk,
"order_no": orderNo,
};
}
void main() {
runApp(MyApp());
}
class MyApp extends StatelessWidget {
@override
Widget build(BuildContext context) {
return MaterialApp(
title: 'Flutter Demo',
theme: ThemeData(
primarySwatch: Colors.blue,
visualDensity: VisualDensity.adaptivePlatformDensity,
),
home: MyHomePage(title: 'Flutter Demo Home Page'),
);
}
}
class MyHomePage extends StatefulWidget {
MyHomePage({Key key, this.title}) : super(key: key);
final String title;
@override
_MyHomePageState createState() => _MyHomePageState();
}
class _MyHomePageState extends State<MyHomePage> {
Future<Payload> _future;
Future<Payload> getData() async {
String jsonString = '''
{
"error": "false",
"content": {
"16": [
[
{
"sod_pk": "31688",
"soh_fk": "23660",
"sqd_fk": "33294",
"order_header": {
"soh_pk": "23660",
"order_no": "16"
}
}
],
[
{
"sod_pk": "31689",
"soh_fk": "23660",
"sqd_fk": "33293",
"order_header": {
"soh_pk": "23660",
"order_no": "16"
}
}
]
],
"18": [
[
{
"sod_pk": "31744",
"soh_fk": "23702",
"sqd_fk": "33354",
"order_header": {
"soh_pk": "23702",
"order_no": "18"
}
}
],
[
{
"sod_pk": "31745",
"soh_fk": "23702",
"sqd_fk": "33356",
"order_header": {
"soh_pk": "23702",
"order_no": "18"
}
}
]
]
}
}
''';
http.Response response = http.Response(jsonString, 200);
if (response.statusCode == 200) {
return payloadFromJson(response.body);
}
}
@override
void initState() {
_future = getData();
super.initState();
}
@override
Widget build(BuildContext context) {
return Scaffold(
appBar: AppBar(
title: Text(widget.title),
),
body: FutureBuilder(
future: _future,
builder: (context, AsyncSnapshot<Payload> snapshot) {
switch (snapshot.connectionState) {
case ConnectionState.none:
return Text('none');
case ConnectionState.waiting:
return Center(child: CircularProgressIndicator());
case ConnectionState.active:
return Text('');
case ConnectionState.done:
if (snapshot.hasError) {
return Text(
'${snapshot.error}',
style: TextStyle(color: Colors.red),
);
} else {
return ListView.separated(
separatorBuilder: (BuildContext context, int index) {
return SizedBox(
height: 30,
);
},
itemCount: snapshot.data.content.keys.length,
itemBuilder: (context, index) {
String key =
snapshot.data.content.keys.elementAt(index);
return Column(
children: [
Text(key),
ListView.separated(
separatorBuilder:
(BuildContext context, int index) {
return SizedBox(
height: 10,
);
},
shrinkWrap: true,
itemCount: snapshot.data.content[key].length,
itemBuilder: (context, index) {
return Column(
children: [
Text(snapshot
.data.content[key][index][0].sodPk),
Text(snapshot
.data.content[key][index][0].sqdFk),
Text(snapshot.data.content[key][index][0]
.orderHeader.sohPk),
],
);
},
)
],
);
});
}
}
}));
}
}
回答2:
Your json is not optimize so difficult to handle.
First of all, you see your json['content'] is not a list so you can't use foreach to get data. It is a object (map) {...}. But flutter don't know exactly it is map of what so you have to cast it. Secondly, to get sod_pk for example you have through 2 list. It's unnecessary. Here is the code
final content = (data['content'] as Map<String, dynamic>);
final sod_pk = content['16'].first.first['sod_pk'];
print(sod_pk);
来源：https://stackoverflow.com/questions/63555004/not-able-to-fetch-json-values-to-field-in-flutter