Can't parse JSON data to listview(_TypeError (type '_InternalLinkedHashMap<String, dynamic>' is not a subtype of type 'FutureOr<List<dynamic>>')

Question

Cant parse JSON data from a URL, getting error "_TypeError (type '_InternalLinkedHashMap' is not a subtype of type 'FutureOr>')". So You can check the datas from the link. and let me know what I am doing wrong, Thanks in advance.

I tried using map, not worked.

import 'package:flutter/material.dart';
import 'dart:async';
import 'dart:convert';
import 'package:http/http.dart' as http;

void main() => runApp(MyApp());

class MyApp extends StatelessWidget {
  // This widget is the root of your application.
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      title: 'Flutter Demo',
        primarySwatch: Colors.blue,
      ),
      home: ui_hotel_list(),
    );
  }
}



class ui_hotel_list extends StatefulWidget {
  @override
  _ui_hotel_listState createState() => _ui_hotel_listState();
}

class _ui_hotel_listState extends State<ui_hotel_list> {
  List hotels;
  Future<List> _getHotels() async {
    String serviceURL="**************************************************************************************";
    var response = await http.get(serviceURL);


    return json.decode(response.body.toString());
  }
  printv() async {
    hotels= await _getHotels();
    for(var i=0;i<hotels.length;i++) {
      print(hotels[i]["hotels"]["name"]);
    }

  }
  @override
  void initState() {
    // TODO: implement initState
    super.initState();
    this._getHotels();
    this.printv();
  }

  @override
  Widget build(BuildContext context) {
    return Container(
      child: ListView.builder(
        padding: EdgeInsets.all(10),
        itemCount: hotels.length==0?0:hotels.length,
        itemBuilder: (BuildContext context, int index){
          return ListTile(
            title: Text(hotels[index]["hotels"]["name"]),
            subtitle:Text(hotels[index]["hotels"]["location"]),
          );
        },
      ),
    );
  }
}

I want to get the data from that URL and show in my listview. What i need to add, please suggest me, thanks.

Answer 1

You need dynamic and access like this
You can paste and run full code below

code snippet

for (var i = 0; i < responseData["hotels"].length; i++) {
      print(responseData["hotels"][i]["name"]);
    }

...
ListTile(
                    title: Text(responseData["hotels"][index]["name"]),
                    subtitle: Text(responseData["hotels"][index]["location"]),
                  ),　　　　

full code

import 'package:flutter/material.dart';
import 'dart:async';
import 'dart:convert';
import 'package:http/http.dart' as http;

void main() => runApp(MyApp());

class MyApp extends StatelessWidget {
  // This widget is the root of your application.
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      title: 'Flutter Demo',
      theme: ThemeData(
        primarySwatch: Colors.blue,
      ),
      home: ui_hotel_list(),
    );
  }
}

class ui_hotel_list extends StatefulWidget {
  @override
  _ui_hotel_listState createState() => _ui_hotel_listState();
}

class _ui_hotel_listState extends State<ui_hotel_list> {
  dynamic responseData;
  bool loading = false;

  Future<dynamic> _getHotels() async {
    setState(() {
      loading = true;
    });
    String serviceURL =
        "https://baseURL/api/v2/search/filtered/?checkin=08-11-2019&checkout=09-11-2019&adults=2&rooms=1&location=1&page=1";
    var response = await http.get(serviceURL);

    return json.decode(response.body.toString());
  }

  printv() async {
    responseData = await _getHotels();
    setState(() {
      loading = false;
    });

    for (var i = 0; i < responseData["hotels"].length; i++) {
      print(responseData["hotels"][i]["name"]);
    }
  }

  @override
  void initState() {
    // TODO: implement initState
    super.initState();
    this._getHotels();
    this.printv();
  }

  @override
  Widget build(BuildContext context) {
    return loading
        ? Container(height: 100, width: 100, child: CircularProgressIndicator())
        : Container(
            child: ListView.builder(
              padding: EdgeInsets.all(10),
              itemCount: responseData["hotels"].length,
              itemBuilder: (BuildContext context, int index) {
                return Card(
                  child: ListTile(
                    title: Text(responseData["hotels"][index]["name"]),
                    subtitle: Text(responseData["hotels"][index]["location"]),
                  ),
                );
              },
            ),
          );
  }
}

Answer 2

It seems to me that the problem comes from the _getHotels() method. It says it returns a Future<List>, because that is what you expect. But Flutter has no way to know what the URL you provided holds (https://amarroom...). It turns out that when you post an HTTP request with that URL, it returns:

{
"special_amenities": [
    1,
    5,
    11,
    48,
    45
],
"facets": {
    "neighborhood": [
        [
...
}

which is not a List, it is a JSON, that is, a Map<String, dynamic> in Dart. So your _getHotels() function should not return a Future<List>, it should return a Future<Map<String, dynamic>>.

Then you can do whatever you want to your Map<String, dynamic> returning from that function and turn it into a List, if that is what you need.