如何遍历属于键值的对象数组-Flutter
我有一个称为锚的数据列表，它具有指向详细屏幕的链接。每个锚都有分布中心，分布中心是嵌套对象的数组。因此，我能够将每个锚点的ID解析到一个详细的屏幕，而
面临一个挑战，即要遍历子项（即锚点的分发中心）。请任何人帮助我，我能够将属于锚的所有值拉到详细屏幕，但是如何在详细屏幕中循环嵌套值是一个问题。嵌套值是下面数组中的DistributionCentres。请任何人可以帮助我进一步学习颤振吗？
json数组：
{ "Anchors": [
{
"Oid": 11,
"Name": "MAIZE ASSOCIATION OF NIGERIA",
"Acronym": "MAAN",
"DistributionCentres": [
{
"Oid": 11,
"Name": "Logo Centre (Zone A)",
"Address": "Private Warehouse, Ugba, Logo LGA"
},
{
"Oid": 12,
"Name": "Makurdi Centre (Zone B)",
"Address": "Ministry of Agric, Makurdi "
},
{
"Oid": 13,
"Name": "Oturkpo Centre (Zone C)",
"Address": "Private Warehouse, Oturkpo"
},
{
"Oid": 15,
"Name": "Borno MAAN centre",
"Address": "Bolori Store, Flavour Mill, Behind Vita Foam, Maiduguri"
},
{
"Oid": 18,
"Name": "Bauchi Centre",
"Address": "BASPD, Dass Road, Bauchi"
}
],
"NoOfDistributionCentres": 5
},
{
"Oid": 2,
"Name": "MAIZE GROWERS, PROCESSORS AND MARKETERS ASSOCIATION OF NIGERIA",
"Acronym": "MAGPAMAN",
"DistributionCentres": [
{
"Oid": 2,
"Name": "Guma Centre",
"Address": "P 32, 2nd Avenue Federal Housing Estate, N/Bank, Makurdi"
},
{
"Oid": 3,
"Name": "Logo Centre",
"Address": "Terhemen Akema Storage Facility, Ugba, Logo LGA"
},
{
"Oid": 5,
"Name": "Oturkpo Centre",
"Address": "Grain Store, Lower Benue Okele Project, Otukpo"
},
{
"Oid": 6,
"Name": "Gboko Centre",
"Address": "K3 New Road, Opposite former coca cola plant. Solar Schools Street, Gboko"
},
{
"Oid": 7,
"Name": "Gwer East Centre",
"Address": "Ahua Shardye's Warehouse, Behind Sylkan Filling Station, Ikpayongo , G/East LGA"
},
{
"Oid": 8,
"Name": "Kwande Centre",
"Address": "KM 3, Adagi Road, Adikpo"
},
{
"Oid": 9,
"Name": "Ohimini Centre",
"Address": "Ajoga Oglewu, Ohimini"
},
{
"Oid": 10,
"Name": "Oju Centre",
"Address": "Behind Town Hall, Ohuhu owo, Oju LGA"
}
],
"NoOfDistributionCentres": 8
}
],
}
锚点页面，其中包含指向详细屏幕的链接：
import 'package:erg_app/AnchorDetails.dart';import 'package:erg_app/Details.dart';
import 'package:erg_app/StockPage.dart';
import 'package:flutter/material.dart';
import 'package:erg_app/Widgets/nav-drawer.dart';
import 'dart:convert';
import 'package:shared_preferences/shared_preferences.dart';
void main() => runApp(MaterialApp(
home: AnchorsPage(),
));
class AnchorsPage extends StatefulWidget {
@override
_MyHomeState createState() => _MyHomeState();
}
class _MyHomeState extends State<AnchorsPage> {
var user;
var userData;
List <dynamic> anchors = [];
@override
void initState() {
_getUserAnchor();
super.initState();
}
_getUserAnchor() async {
SharedPreferences localStorage = await SharedPreferences.getInstance();
var userJson = localStorage.getString('loginRes');
user = json.decode(userJson);
setState(() {
anchors = user['Anchors'];
});
print(anchors);
setState(() {
userData = anchors;
});
}
@override
Widget build(BuildContext context) {
return Scaffold(
drawer: NavDrawer(),
appBar: AppBar(
title: Text('Anchors Details'),
iconTheme: IconThemeData(color: Colors.white),
backgroundColor: Colors.green,
),
body: Container(
padding: const EdgeInsets.fromLTRB(10, 30, 10, 10),
child: ListView(
children: <Widget>[
Row(
mainAxisAlignment: MainAxisAlignment.spaceAround,
children: <Widget>[
Icon(Icons.card_membership,
size: 35, color: Colors.orange[400]),
Text(
'Assigned Anchors',
style: TextStyle(color: Colors.orange[400], fontSize: 25),
),
],
),
ListView.builder(
shrinkWrap: true,
itemCount: anchors.length,
physics: NeverScrollableScrollPhysics(),
itemBuilder: (BuildContext context, int i) {
return Padding(
padding: const EdgeInsets.all(10.0),
////////////// 1st card///////////
child: Card(
elevation: 4.0,
color: Colors.grey[100],
margin: EdgeInsets.only(
left: 10, right: 10, top: 20, bottom: 10),
shape: RoundedRectangleBorder(
borderRadius: BorderRadius.circular(10)),
child: Container(
padding: EdgeInsets.only(left: 15, top: 20, bottom: 10),
width: MediaQuery.of(context).size.width,
child: Column(
crossAxisAlignment: CrossAxisAlignment.start,
children: <Widget>[
Row(
children: <Widget>[
Padding(
padding: const EdgeInsets.all(8.0),
child: Container(
width: 50.0,
height: 50.0,
decoration: new BoxDecoration(
shape: BoxShape.circle,
image: new DecorationImage(
fit: BoxFit.cover,
image: AssetImage(
'assets/images/user.png')))),
),
SizedBox(
width: 20,
),
Text(
anchors[i]['Acronym'],
textAlign: TextAlign.center,
style: TextStyle(
color: Color(0xFF9b9b9b),
fontSize: 20,
decoration: TextDecoration.none,
fontWeight: FontWeight.normal,
),
),
],
),
Container(width: 10),
Row(
children: <Widget>[
Padding(
padding:
const EdgeInsets.only(left: 10, top: 10),
child: Text(
'Allocated Farmers:',
textAlign: TextAlign.left,
style: TextStyle(
color: Color(0xFF9b9b9b),
fontSize: 14.0,
decoration: TextDecoration.none,
fontWeight: FontWeight.normal,
),
),
),
Padding(
padding:
const EdgeInsets.only(left: 70, top: 12),
child: Text(
anchors[i]['Oid'].toString(),
textAlign: TextAlign.left,
style: TextStyle(
color: Colors.grey[700],
fontSize: 14.0,
decoration: TextDecoration.none,
fontWeight: FontWeight.normal,
),
),
),
],
),
Container(
height: 20,
),
Row(
children: <Widget>[
/////////// Buttons /////////////
Padding(
padding: const EdgeInsets.all(10.0),
child: FlatButton(
child: Padding(
padding: EdgeInsets.only(
top: 8,
bottom: 8,
left: 10,
right: 8),
child: Text(
'View Details',
textDirection: TextDirection.ltr,
style: TextStyle(
color: Colors.white,
fontSize: 15.0,
decoration: TextDecoration.none,
fontWeight: FontWeight.normal,
),
),
),
color: Colors.blueGrey,
shape: new RoundedRectangleBorder(
borderRadius:
new BorderRadius.circular(
20.0)),
onPressed: () {
Navigator.push(
context,
new MaterialPageRoute(
builder: (context) =>
detailsPage(value : anchors)));
},
),
),
/////////// End of Buttons /////////////
],
),
],
),
),
),
);
})
],
),
),
);
}
}
详细画面：
import 'package:flutter/material.dart';class detailsPage extends StatefulWidget {
dynamic value;
detailsPage({Key key, @required this.value}) : super(key: key);
@override
_detailsPageState createState() => _detailsPageState(value);
}
class _detailsPageState extends State<detailsPage> {
dynamic value;
_detailsPageState(this.value);
@override
Widget build(BuildContext context) {
return Scaffold(
appBar: AppBar(
title: Text("Anchors Details Page"),
iconTheme: IconThemeData(color: Colors.white),
backgroundColor: Colors.green,
),
// body: Center(
// child: Text(
// value[1]['Name'].toString(),
// ),
// ),
body: Column(
children: <Widget>[
Padding(
padding: const EdgeInsets.all(8.0),
child: Card(
child: Column(
children: <Widget>[
Text(value[1]['Name']),
Text(value[1]['Oid'].toString()),
//Text(value [1]['DistributionCentres']),
],
),
),
),
],
),
);
}
}
回答：
我建议您在这种情况下使用数据类。
import 'package:flutter/material.dart';List<Anchor> _parseAnchors(Map<String, dynamic> map) {
final anchors = <Anchor>[];
for (var anchorMap in map['Anchors']) {
final anchor = Anchor.fromMap(anchorMap);
anchors.add(anchor);
}
return anchors;
}
class Anchor {
final int oId;
final String name;
final String acronym;
final List<DistributionCenter> distributionCenters;
const Anchor({
@required this.oId,
@required this.name,
@required this.acronym,
@required this.distributionCenters,
});
factory Anchor.fromMap(Map<String, dynamic> map) {
final distributionCenters = <DistributionCenter>[];
for (var distribution in map['DistributionCentres']) {
final distributionCenter = DistributionCenter.fromMap(distribution);
distributionCenters.add(distributionCenter);
}
return Anchor(
oId: map['Oid'] as int,
name: map['Name'] as String,
acronym: map['Acronym'] as String,
distributionCenters: distributionCenters,
);
}
}
class DistributionCenter {
final int id;
final String name;
final String address;
const DistributionCenter({
@required this.id,
@required this.name,
@required this.address,
});
factory DistributionCenter.fromMap(Map<String, dynamic> map) {
return DistributionCenter(
id: map['Oid'] as int,
name: map['Name'] as String,
address: map['Address'] as String,
);
}
}
class AnchorPage extends StatelessWidget {
// details page
final Anchor anchor;
@override
const AnchorPage({Key key, @required this.anchor}) : super(key: key);
Widget build(BuildContext context) {
return Scaffold(
body: Container(
child: Text(anchor.name),
),
);
}
}
class AnchorsPage extends StatefulWidget {
const AnchorsPage({Key key}) : super(key: key);
@override
_AnchorsPageState createState() => _AnchorsPageState();
}
class _AnchorsPageState extends State<AnchorsPage> {
static const anchorsMap = {
"Anchors": [
{
"Oid": 11,
"Name": "MAIZE ASSOCIATION OF NIGERIA",
"Acronym": "MAAN",
"DistributionCentres": [
{
"Oid": 11,
"Name": "Logo Centre (Zone A)",
"Address": "Private Warehouse, Ugba, Logo LGA"
},
{
"Oid": 12,
"Name": "Makurdi Centre (Zone B)",
"Address": "Ministry of Agric, Makurdi "
},
{
"Oid": 13,
"Name": "Oturkpo Centre (Zone C)",
"Address": "Private Warehouse, Oturkpo"
},
{
"Oid": 15,
"Name": "Borno MAAN centre",
"Address": "Bolori Store, Flavour Mill, Behind Vita Foam, Maiduguri"
},
{
"Oid": 18,
"Name": "Bauchi Centre",
"Address": "BASPD, Dass Road, Bauchi"
}
],
"NoOfDistributionCentres": 5
},
{
"Oid": 2,
"Name":
"MAIZE GROWERS, PROCESSORS AND MARKETERS ASSOCIATION OF NIGERIA",
"Acronym": "MAGPAMAN",
"DistributionCentres": [
{
"Oid": 2,
"Name": "Guma Centre",
"Address":
"P 32, 2nd Avenue Federal Housing Estate, N/Bank, Makurdi"
},
{
"Oid": 3,
"Name": "Logo Centre",
"Address": "Terhemen Akema Storage Facility, Ugba, Logo LGA"
},
{
"Oid": 5,
"Name": "Oturkpo Centre",
"Address": "Grain Store, Lower Benue Okele Project, Otukpo"
},
{
"Oid": 6,
"Name": "Gboko Centre",
"Address":
"K3 New Road, Opposite former coca cola plant. Solar Schools Street,
Gboko"
},
{
"Oid": 7,
"Name": "Gwer East Centre",
"Address":
"Ahua Shardye's Warehouse, Behind Sylkan Filling Station, Ikpayongo ,
G/East LGA"
},
{
"Oid": 8,
"Name": "Kwande Centre",
"Address": "KM 3, Adagi Road, Adikpo"
},
{
"Oid": 9,
"Name": "Ohimini Centre",
"Address": "Ajoga Oglewu, Ohimini"
},
{
"Oid": 10,
"Name": "Oju Centre",
"Address": "Behind Town Hall, Ohuhu owo, Oju LGA"
}
],
"NoOfDistributionCentres": 8
}
],
};
final _anchors = <Anchor>[];
@override
Widget build(BuildContext context) {
// now you can use the anchors list here
return Scaffold(
body: ListView.builder(
itemCount: _anchors.length,
itemBuilder: (context, index) {
final anchor = _anchors[index];
return ListTile(
title: Text(anchor.name),
subtitle: Text(anchor.acronym),
trailing: Text(anchor.distributionCenters?.length?.toString()),
onTap: () {
Navigator.push(
context,
MaterialPageRoute(
builder: (context) => AnchorPage(anchor: anchor),
),
);
},
);
},
),
);
}
@override
void initState() {
super.initState();
final anchors = _parseAnchors(anchorsMap);
_anchors.addAll(anchors);
}
}
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