问题
I am new to flutter this error is giving me a serious nightmare. I have a card list of items called Anchors. These items are coming from the shared preference file which belongs to the logged-in user. In the shared preference Json file, each anchor has one or more distribution centers nested to it. All in a JSON form stored in the shared Preference. Now, I was able to iterate over the anchors respectfully at the first screen but the challenge I am having is when I click on view anchor details button instead of taking me to the details page where I can view the details of that anchor and iterate over the distribution centers of that anchor it doesn't but instead it takes the whole anchors there. I tried to parse only one id to the details page so I can Iterate over the nested objects of that anchor but still its not working. The error message says: type 'int' is not a subtype of type 'List' But if I remove [i]['Oid'] from the link to the details screen it takes the whole data there. They are all on two different screens. Please can anybody help me?
JSON format of:
"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
}
],
Anchors Page:
import 'package:erg_app/Details.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();
}
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 _MyHomeState extends State<AnchorsPage> {
var user;
var userData;
List 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,
),
),
),
],
),
Row(
children: <Widget>[
Padding(
padding:
const EdgeInsets.only(left: 10, top: 10),
child: Text(
'Validated 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,
),
),
),
],
),
Row(
children: <Widget>[
Padding(
padding:
const EdgeInsets.only(left: 10, top: 10),
child: Text(
'Non Validated Farmers:',
textAlign: TextAlign.left,
style: TextStyle(
color: Color(0xFF9b9b9b),
fontSize: 14.0,
decoration: TextDecoration.none,
fontWeight: FontWeight.normal,
),
),
),
Padding(
padding:
const EdgeInsets.only(left: 40, 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,
),
),
),
],
),
Row(
children: <Widget>[
Padding(
padding:
const EdgeInsets.only(left: 10, top: 10),
child: Text(
'Distribution Centers:',
textAlign: TextAlign.left,
style: TextStyle(
color: Color(0xFF9b9b9b),
fontSize: 14.0,
decoration: TextDecoration.none,
fontWeight: FontWeight.normal,
),
),
),
Padding(
padding:
const EdgeInsets.only(left: 60, 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,
),
),
),
],
),
Row(
children: <Widget>[
Padding(
padding:
const EdgeInsets.only(left: 10, top: 10),
child: Text(
'Daily Inventory Status:',
textAlign: TextAlign.left,
style: TextStyle(
color: Color(0xFF9b9b9b),
fontSize: 14.0,
decoration: TextDecoration.none,
fontWeight: FontWeight.normal,
),
),
),
Padding(
padding:
const EdgeInsets.only(left: 50, top: 12),
child: Text(
'3',
textAlign: TextAlign.left,
style: TextStyle(
color:Colors.green,
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[i]['Oid'])));
},
),
),
/////////// End of Buttons /////////////
],
),
],
),
),
),
);
})
],
),
),
);
}
}
Details Page:
import 'package:flutter/material.dart';
class detailsPage extends StatefulWidget {
List value;
detailsPage({Key key, @required this.value}) : super(key: key);
@override
_detailsPageState createState() => _detailsPageState(value);
}
class _detailsPageState extends State<detailsPage> {
List 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: Container(
child: ListView(
children: <Widget>[
Text(value[1]['Name']),
Text(value[1]['Oid'].toString()),
ListView.builder(
shrinkWrap: true,
itemCount: value[1]['DistributionCentres'].length,
//context:context, //it saying the name parameter context is not defined
physics: NeverScrollableScrollPhysics(),
itemBuilder: (BuildContext context, int i) {
return Text(value[1]['DistributionCentres'][i]['Name']);
})
],
),
),
);
}
}
Image of what I want to achieve below:
回答1:
first screen onPressed get the index and assigned it to variable, or you can just pass i varibale too,
onPressed: () {
Navigator.push(context,new MaterialPageRoute(builder: (context) =>
detailsPage(i))); },
In detailed page
class detailsPage extends StatefulWidget {
final int selectedIndex;
detailsPage(this.selectedIndex,{Key key}) : super(key: key);
@override
_detailsPageState createState() => _detailsPageState();
}
place that you want to use the previous page passsed index,
return Text(value[widget.selectedIndex]['DistributionCentres'][i]['Name']);
Hope this will help..
回答2:
The problem seems to be here
detailsPage(value : anchors[i]['Oid'])
You're passing Oid as parameter that is an Int. But look that the constructor for detailsPage
List value;
detailsPage({Key key, @required this.value}) : super(key: key);
The parameter value is a List. It's hard for me to know what you're trying to do... but you will need to fix this type mismatch.
EDIT
It seems that value parameter should be of type Map<String,dynamic>
class detailsPage extends StatefulWidget {
Map<String, dynamic> value;
detailsPage({Key key, @required this.value}) : super(key: key);
@override
_detailsPageState createState() => _detailsPageState(value);
}
class _detailsPageState extends State<detailsPage> {
Map<String, 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: Container(
child: ListView(
children: <Widget>[
Text(value['Name']),
Text(value['Oid'].toString()),
ListView.builder(
shrinkWrap: true,
itemCount: value['DistributionCentres'].length,
//context:context, //it saying the name parameter context is not defined
physics: NeverScrollableScrollPhysics(),
itemBuilder: (BuildContext context, int i) {
return Text(value['DistributionCentres'][i]['Name']);
})
],
),
),
);
}
}
And then you should do
detailsPage(value : anchors[i])));
来源：https://stackoverflow.com/questions/62575057/how-can-i-view-the-details-of-an-item-in-a-detailed-screen-flutter