I want to fetch price data of trading pairs specified inpriceList from the public Binance API and create a dynamic List of Card widgets using API response. I am failing at this step as the future argument of FutureBuilder does not accept the list of Futures : List<Future<PriceListItem>> pliList

Thank you.

My code:

import 'dart:convert';

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

void main() {
  runApp(MaterialApp(
    title: 'Flutter Demo',
    theme: ThemeData(
      primarySwatch: Colors.blue,
    ),
    home: const HomePage(),
  ));
}

class HomePage extends StatefulWidget {
  const HomePage({Key? key}) : super(key: key);

  @override
  State<HomePage> createState() => _HomePageState();
}

class PriceListItem {
  final String pair;
  final String price;

  PriceListItem({
    required this.pair,
    required this.price,
  });
  factory PriceListItem.fromJson(Map<String, dynamic> json) {
    return PriceListItem(
      pair: json['symbol'],
      price: json['price'],
    );
  }
}

class _HomePageState extends State<HomePage> {
  List<String> pairList = [
    "USTBUSD",
    "USTUSDT",
    "USDCBUSD",
    "USDCUSDT",
    "BUSDUSDT",
    "BTCBUSD",
    "USTBTC",
    "BTCUSDT",
    "BTCUSDC",
  ];
  late Future<PriceListItem> pli;
  late List<Future<PriceListItem>> pliList;

  Future<PriceListItem> fetchPrice(String ticker) async {
    final response = await http.get(Uri.parse(
        "https://api.binance.com/api/v3/ticker/price?symbol=$ticker"));

    if (response.statusCode == 200) {
      return PriceListItem.fromJson(jsonDecode(response.body));
    } else {
      throw Exception("Failed to fetch price data.");
    }
  }

  @override
  void initState() {
    pliList = [];
    for (int i = 0; i < pairList.length; i  ) {
      pli = fetchPrice(pairList[i]);
      pliList.add(pli);
    }
    super.initState();
  }

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: const Text("price tracker"),
      ),
      body: Column(
        children: [
          FutureBuilder<PriceListItem>(
            future: pliList, //The argument type 'List<Future<PriceListItem>>' can't be assigned to the parameter type 'Future<PriceListItem>?'.dartargument_type_not_assignable
            builder: (context, snapshot) {
              if (snapshot.hasData) {
                return ListView.builder(
                  itemCount: 2,
                  physics: const ScrollPhysics(),
                  padding: const EdgeInsets.all(8),
                  shrinkWrap: true,
                  itemBuilder: (BuildContext context, int index) {
                    return Card(
                      child: ListTile(
                        title: Text(snapshot.data!.price),
                        subtitle: Text(snapshot.data!.pair),
                        trailing: const Icon(Icons.currency_bitcoin),
                        onTap: () {},
                      ),
                    );
                  },
                );
              } else if (snapshot.hasError) {
                return Text('${snapshot.error}');
              }
              return const CircularProgressIndicator();
            },
          )
        ],
      ),
    );
  }
}

CodePudding user response：

Do it like this this:

FutureBuilder<List<PriceListItem>>(
  future: Future.wait(pliList),  
  builder: (context, snapshot) {
 
}

https://api.flutter.dev/flutter/dart-async/Future/wait.html