Flutter JSON 无法正确读取

Question

这可能需要一段时间... 我一直在尝试让我的 Dart/Flutter 代码从 BlockChainTicker 返回数据（特别是我想查看 AUD 行中的所有内容）并将其留在调试控制台中。当我这样做时，我会从控制台返回此错误

E/flutter ( 8656): [ERROR:topaz/lib/tonic/logging/dart_error.cc(16)] Unhandled exception:
E/flutter ( 8656): type '_InternalLinkedHashMap<String, dynamic>' is not a subtype of type 'List' where
E/flutter ( 8656):   _InternalLinkedHashMap is from dart:collection
E/flutter ( 8656):   String is from dart:core
E/flutter ( 8656):   List is from dart:core

我的代码可能看起来很陌生，但我只有大约一周的这门语言经验，所以感谢您耐心阅读本文。

import 'dart:async';
import 'dart:convert';

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



class First extends StatefulWidget {
  @override
  HomePageState createState() => new HomePageState();
}

class HomePageState extends State<First> {

  List data;

  Future<String> getData() async {
    var response = await http.get(
      Uri.encodeFull("http://blockchain.info/ticker"),
      headers: {
        "Accept": "application/json"
      }
    );
    data = JSON.decode(response.body);
    print(data[1]["AUD"]);

    return "Success!";
  }

  @override
  Widget build(BuildContext context) {
    return new Scaffold(
      body: new Center(
        child: new RaisedButton(
          child: new Text("Get data"),
          onPressed: getData,
        ),
      ),
    );
  }
}

Answer 1

您的 json 的顶层是一个地图（不是列表 - 在 json 中，列表括在括号中）

{
  "USD" : {"15m" : 7492.85, "last" : 7492.85, "buy" : 7492.85, "sell" : 7492.85, "symbol" : "$"},
  "AUD" : {"15m" : 9899.28, "last" : 9899.28, "buy" : 9899.28, "sell" : 9899.28, "symbol" : "$"},
  "BRL" : {"15m" : 28214.31, "last" : 28214.31, "buy" : 28214.31, "sell" : 28214.31, "symbol" : "R$"},

所以改变：

print(data[1]["AUD"]);

到

print(data["AUD"]); // prints the whole AUD map
print(data['AUD']['last']); // prints the AUD 'last' double

String isoCode = 'AUD';
print('$isoCode -> ${data[isoCode]}');