Flutter 颤振：如何从附加对象在字幕中添加附加值

如何在附加对象的字幕中添加附加值

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

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

Future<List<Photo>> fetchPhotos(http.Client client) async {
  final response =
  await client.get('https://cloud.iexapis.com/stable/stock/market/batch?symbols=SLVO,GLDI,SPFF,CNPF,MONY&types=quote,**stats**&token=');

  // Use the compute function to run parsePhotos in a separate isolate.
  return compute(parsePhotos, response.body);
}

// A function that converts a response body into a List<Photo>.
List<Photo> parsePhotos(String responseBody) {
  //final parsed = json.decode(responseBody).cast<Map<String, dynamic>>();

  //return parsed.map<Photo>((json) => Photo.fromJson(json)).toList();

  dynamic Obj = json.decode(responseBody);
  print(Obj.length);
  List<Photo> photoList = [];
  Obj.forEach((k, v,y) => photoList.add(Photo(k,v,y)));

  return photoList;
}

class Photo {
  String symbol;
 dynamic data;
  dynamic stats;
  Photo(this.symbol ,this.data, this.stats);
}

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

class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    final appTitle = 'Isolate Demo';

    return MaterialApp(
      title: appTitle,
      home: MyHomePage(title: appTitle),
    );
  }
}

class MyHomePage extends StatelessWidget {
  final String title;

  MyHomePage({Key key, this.title}) : super(key: key);

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: Text(title),
      ),
      body: FutureBuilder<List<Photo>>(
        future: fetchPhotos(http.Client()),
        builder: (context, snapshot) {
          if (snapshot.hasError) print(snapshot.error);

          return snapshot.hasData
              ? PhotosList(photos: snapshot.data)
              : Center(child: CircularProgressIndicator());
        },
      ),
    );
  }
}

class PhotosList extends StatelessWidget {
  final List<Photo> photos;

  PhotosList({Key key, this.photos}) : super(key: key);

  @override
  Widget build(BuildContext context) {
    return GridView.builder(
      gridDelegate: SliverGridDelegateWithFixedCrossAxisCount(
        crossAxisCount: 2,
      ),
      itemCount: photos.length,
      itemBuilder: (context, index) {
        return ListTile(
          leading: Icon(Icons.album),
          subtitle: Column(
            children: [
             // Text( ' ${photos[index].stats["stats"]["dividendYield"]["companyName"]}'),
            //  Text( ' ${photos[index].data["quote"]["iexRealtimePrice"]}' ' ${photos[index].stats["stats"]["dividendYield"]["companyName"]}'),
              Text( ' ${photos[index].data["quote"]["iexRealtimePrice"]}'),
              Text ( ' ${photos[index].stats["stats"]["dividendYield"]}'),
            ],
          ),
         //title: Text(photos[index].symbol),
         //subtitle: Text( ' ${photos[index].stats["stats"]["dividendYield"]["companyName"]}'),
          //subtitle: Text( ' ${photos[index].data["quote"]["iexRealtimePrice"]}' ' ${photos[index].stats["stats"]["dividendYield"]["companyName"]}'),
       // subtitle: Text( ' ${photos[index].data["quote"]["iexRealtimePrice"]}'),
         // subtitle: Text ( ' ${photos[index].stats["stats"]["dividendYield"]}'),
        );
      },
    );
  }
}

Json

{“SLVO”：{“统计数据”：{“week52change”：0.047256，“week52high”：7.48，“week52low”：6.23，“marketcap”：null，“employees”：null，“day200MovingAvg”：6.88，“day50MovingAvg”：7.13，“float”：null，“avg10Volume”：7454.8，“avg30Volume”：7927.83，“ttmEPS”：null，“TTMDidendrate”：null，“companyName”：“瑞士信贷X-Links白银股票套保买入ETN”，“sharesOutstanding”：0，“maxChangePercent”：58.7391，“year5ChangePercent”：-0.4128，“year2ChangePercent”：-0.1369，“year1ChangePercent”：0.047256，“ytdChangePercent”：-0.005789，“month6ChangePercent”：0.074445，“month3ChangePercent”：-0.035112，“month1ChangePercent”：-0.025532，“day30ChangePercent”：-0.035112，“day5ChangePercent”：-0.007225，“nextDividendDate”：null，”dividendYield:null，“nextearningdate”：null，“exDividendDate”：null，“peRatio”：null，“beta”：-0.06347545711182472}，“quote”：{“symbol”：“SLVO”，“companyName”：“瑞士信贷X-Links银股备兑看涨ETN”，“primaryExchange”：“纳斯达克”，“计算价格”：“收盘”，“开盘”：6.89，“开盘时间”：157436600589，“收盘时间”：6.88，“收盘时间”“：157437000242，“高”：6.9，“低”：6.87，“最新价格”：6.88，“最新来源”：“关闭”，“最晚时间”：“11月21日

添加： &类型=统计数据，引用和标记

除了副标题中的价格之外，我还想要例如：

第52周更改“：0.047256或marketcap”：空

---

也许可以使用

列

  leading: Icon(Icons.album),
  title: Text(photos[index].symbol),
  subtitle: Column(
    children: [
      Text( ' ${photos[index].stats["stats"]["dividendYield"]["companyName"]}'),
      Text( ' ${photos[index].data["quote"]["iexRealtimePrice"]}' ' ${photos[index].stats["stats"]["dividendYield"]["companyName"]}'),
      Text( ' ${photos[index].data["quote"]["stats"]["iexRealtimePrice"]}'),
      Text ( ' ${photos[index].stats["stats"]["dividendYield"]}'),
    ],
  ),
);

---

@chunhunghan刚刚在api json url中添加了“stats”、quote和token。并且希望将附加值打印到副标题中，因为价格为.I/flutter（28902）：══╡ WIDGETS库捕获到异常╞═══════════════════════════════════════════════════════════ I/flatter（28902）：在建筑中抛出了以下NoSuchMethodError:I/flatter（28902）：在null上调用了方法“[]”。I/flatter（28902）：接收方：null I/flatter（28902）：尝试调用：[]（“stats”）@DevEd看起来像

photos[index].stats

则为空。您必须找出原因。@Abion47感谢您提供原始答案。我添加了完整的代码。您能看一下吗？如果json代码有数据，为什么它会为空。

  leading: Icon(Icons.album),
  title: Text(photos[index].symbol),
  subtitle: Column(
    children: [
      Text( ' ${photos[index].stats["stats"]["dividendYield"]["companyName"]}'),
      Text( ' ${photos[index].data["quote"]["iexRealtimePrice"]}' ' ${photos[index].stats["stats"]["dividendYield"]["companyName"]}'),
      Text( ' ${photos[index].data["quote"]["stats"]["iexRealtimePrice"]}'),
      Text ( ' ${photos[index].stats["stats"]["dividendYield"]}'),
    ],
  ),
);