方法'[]'在null上被调用。接收者：null [英] The method '[]' was called on null. Receiver: null
本文介绍了方法'[]'在null上被调用。接收者：null的处理方法，对大家解决问题具有一定的参考价值，需要的朋友们下面随着小编来一起学习吧！
问题描述
为找出问题，我创建了新代码，新程序和新计算机。
结果相同，只是不希望打印引号后具有 anythingPrice之后的任何值
To isolate the issue, I created a new code, a new program, and a new machine. Same results, it just doesn't want to print any value that has is after "quotes and has "anythingPrice"
我可以再次给您一个临时值
Again I can give you a temp key and you can fully run the code. on your side.
请让我知道。
import 'dart:async';
import 'dart:convert';
import 'package:flutter/foundation.dart';
import 'package:flutter/material.dart';
import 'package:http/http.dart' as http;
//import 'package:flutter_web/material.dart';
//import 'package:flutter/main.dart' as app;
//import 'package:flutter_web_ui/ui.dart' as ui;
Future<List<Photo>> fetchPhotos(http.Client client) async {
final response =
// await client.get('https://cloud.iexapis.com/stable/stock/market/batch?symbols=CNPF,ICOL,PGX,MORL,EMLC,GYLD,IPFF,SMB,YDIV,YYY,PEY,IEI,TLH,DIA,BSJF,MONY&types=quote,stats&token=');
await client.get('https://cloud.iexapis.com/stable/stock/market/batch?symbols=PGX,MORL,EMLC,GYLD,IPFF,SMB,YDIV,YYY,PEY,PGF,SNLN,DVHL,AUNZ,MDIV,PHB,PFXF,FPE,TIPX,MLN,SDIV,SIPE,SEMF,EMAG,IEMF,EU,BSCM,LEMF,BSCL,BSCK,BSCJ,BSCI,DSUM,BSCF,KBWD,PCEF,BSCG,BSCH,HYEM,ITM,BKLN,PGHY,IBCE,PZT,IJNK,XMPT,THHY,QYLD,IHY,IYLD,SHYD,PRB,DVHI,GOVT,BSJJ,BSJK,RIGS,INY,IBCD,PZA,PFIG,IBCC,BSCE,PVI,MBG,CXA,FWDB,DIV,CHLC,BSJI,FLTR,PWZ,MUAH,IBDD,PICB,IBDB,BSJH,RVNU,BSJG,IBDC,XOVR,BSJE,EBND,PCY,BWX,SJNK,DES,ANGL,BAB,SST,EMCD,CBND,HYD,PLW,SCPB,FLRN,BWZ,KBWY,ELD,IBND,AOK,RWXL,ITR,DON,DGRS,JNK,TZD,EPU,PFF,HYLD,GGOV,ULST,SPHD,HFIN,DGRW,LWC,ALD,LEMB,AGND,ITIP,EMHY,QLTC,TFI,SRLN,HYLS,SHM,GNMA,CEMB,IGOV,MINC,AGZD,FTSL,SPLV,GHYG,ISTB,ENGN,CMBS,GTIP,SCHO,SMMU,QLTA,SCHZ,HSPX,TUZ,GIY,GSY,TFLO,VMBS,CWB,FLOT,STPZ,MUAC,SCHR,BABZ,HYXU,GMTB,MUNI,WIP,MUAD,QLTB,SCHP,GMMB,MUAE,IPE,NYF,BNDX,MUAF,HYMB,TIPZ,CMF,LAG,ILTB,ITE,CLY,VGSH,VGIT,LTPZ,BABS,HYHG,EMCB,DVYL,VGLT,DHS,TLO,VWOB,IGHG,GLCB,RAVI,VCSH,BSV,BND,BIV,ISHG,SDYL,VCIT,SHY,BLV,HYG,VCLT,TENZ,DTN,BIL,AUD,DLN,DTD,FTSD,CAD,STIP,CORP,HYS,HOLD,TRSY,IEF,IBDA,COBO,BOND,MINT,MBB,CSJ,AGG,SUB,EMB,CIU,GVI,MUB,GBF,TIP,AGZ,CFT,LQD,TLT,IEI,TLH,DIA,BSJF,MONY&types=stats,quote&token=');
//https://cloud.iexapis.com/v1/stock/market/batch?&types=price&symbols=aapl,fb,tsla&token=YOUR_TOKEN_HERE
//https://cloud.iexapis.com/v1/stock/market/batch?&types=quote&symbols=aapl,fb,tsla&token=
// Use the compute function to run parsePhotos in a separate isolate.
//https://cloud.iexapis.com/stable/stock/market/batch?symbols=CNPF,ICOL,PGX,MORL,EMLC,GYLD,IPFF,SMB,YDIV,YYY,PEY,PGF,SNLN,DVHL,AUNZ,MDIV,PHB,PFXF,FPE,TIPX,MLN,SDIV,SIPE,SEMF,EMAG,IEMF,EU,BSCM,LEMF,BSCL,BSCK,BSCJ,BSCI,DSUM,BSCF,KBWD,PCEF,BSCG,BSCH,HYEM,ITM,BKLN,PGHY,IBCE,PZT,IJNK,XMPT,THHY,QYLD,IHY,IYLD,SHYD,PRB,DVHI,GOVT,BSJJ,BSJK,RIGS,INY,IBCD,PZA,PFIG,IBCC,BSCE,PVI,MBG,CXA,FWDB,DIV,CHLC,BSJI,FLTR,PWZ,MUAH,IBDD,PICB,IBDB,BSJH,RVNU,BSJG,IBDC,XOVR,BSJE,EBND,PCY,BWX,SJNK,DES,ANGL,BAB,SST,EMCD,CBND,HYD,PLW,SCPB,FLRN,BWZ,KBWY,ELD,IBND,AOK,RWXL,ITR,DON,DGRS,JNK,TZD,EPU,PFF,HYLD,GGOV,ULST,SPHD,HFIN,DGRW,LWC,ALD,LEMB,AGND,ITIP,EMHY,QLTC,TFI,SRLN,HYLS,SHM,GNMA,CEMB,IGOV,MINC,AGZD,FTSL,SPLV,GHYG,ISTB,ENGN,CMBS,GTIP,SCHO,SMMU,QLTA,SCHZ,HSPX,TUZ,GIY,GSY,TFLO,VMBS,CWB,FLOT,STPZ,MUAC,SCHR,BABZ,HYXU,GMTB,MUNI,WIP,MUAD,QLTB,SCHP,GMMB,MUAE,IPE,NYF,BNDX,MUAF,HYMB,TIPZ,CMF,LAG,ILTB,ITE,CLY,VGSH,VGIT,LTPZ,BABS,HYHG,EMCB,DVYL,VGLT,DHS,TLO,VWOB,IGHG,GLCB,RAVI,VCSH,BSV,BND,BIV,ISHG,SDYL,VCIT,SHY,BLV,HYG,VCLT,TENZ,DTN,BIL,AUD,DLN,DTD,FTSD,CAD,STIP,CORP,HYS,HOLD,TRSY,IEF,IBDA,COBO,BOND,MINT,MBB,CSJ,AGG,SUB,EMB,CIU,GVI,MUB,GBF,TIP,AGZ,CFT,LQD,TLT,IEI,TLH,DIA,BSJF,MONY&types=quote,stats&token=
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);
debugPrint(responseBody, wrapWidth: 8192);
print(Obj.length);
List<Photo> photoList = [];
Obj.forEach((k, v) => photoList.add(Photo(k,v)));
return photoList;
}
class Photo {
String symbol;
//String companyName;
dynamic data;
// dynamic iexClose;
// dynamic quote;
Photo(this.symbol ,this.data);
}
void main() => runApp(MyApp());
class MyApp extends StatelessWidget {
@override
Widget build(BuildContext context) {
final appTitle = 'Monthly Paying ETFs';
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(
drawer: Drawer(
// Add a ListView to the drawer. This ensures the user can scroll
// through the options in the drawer if there isn't enough vertical
// space to fit everything.
child: ListView(
// Important: Remove any padding from the ListView.
padding: EdgeInsets.zero,
children: <Widget>[
DrawerHeader(
child: Text('About'),
decoration: BoxDecoration(
color: Colors.grey,
),
),
ListTile(
title: Text('This app is to provide the list of ETF s that pay monthly dividend'),
onTap: () {
// Update the state of the app
// ...
// Then close the drawer
Navigator.pop(context);
},
),
ListTile(
title: Text('for questions or feedback please contact me at '),
onTap: () {
// Update the state of the app
// ...
// Then close the drawer
Navigator.pop(context);
},
),
],
),
),
appBar: AppBar(
title: Text(title),
backgroundColor: Colors.greenAccent,
),
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 StatefulWidget {
final List photos;
PhotosList({Key key, this.photos})
: assert(photos != null),
super(key: key);
@override
_PhotosListState createState() => _PhotosListState();
}
class _PhotosListState extends State<PhotosList> {
@override
Widget build(BuildContext context) {
return bodyData();
}
SingleChildScrollView bodyData() =>
SingleChildScrollView(
scrollDirection: Axis.vertical,
// padding: EdgeInsets.all(0.0),
//padding: const EdgeInsets.symmetric(
// padding: new EdgeInsets.fromLTRB(0.001, .001, 1.0, 1.0),
padding: EdgeInsets.all(0.05),
// child: FittedBox(fit:BoxFit.contain,
child:SingleChildScrollView(
scrollDirection: Axis.horizontal,
child:
FittedBox(
fit: BoxFit.fitHeight,
child: DataTable(
// sortColumnIndex: 1,
// sortAscending: true,
columns: <DataColumn>[
DataColumn(
label: Text("Company"),
onSort: (_, __) {
setState(() {
widget.photos.sort((a, b) =>
a.data["quote"]["companyName"]
.compareTo(b.data["quote"]["companyName"]));
});
},
),
DataColumn(
label: Text("ttmDivRate"),
numeric: true,
onSort: (_,__) {
setState(() {
widget.photos.sort((a, b) =>
a.data["quote"]["ttmDividendRate"]
.compareTo(b.data["quote"]["ttmDividendRate"]));
});
},
),
DataColumn(
label: Text("Price"),
numeric: true,
onSort: (_, __) {
setState(() {
widget.photos.sort((a, b) => a.data ["quote"]["latestPrice"]
.compareTo(b.data["quote"]["latestPrice"]));
});
},
),
],
rows: widget.photos
.map(
(photo) =>
DataRow(
cells: [
DataCell(
Text('${photo.data["stats"]["companyName"] ?? ""}'),
),
DataCell(
Text('${photo.data["stats"]["ttmDividendRate"] ?? ""}'),
),
//["quote"]["stats"]
DataCell(
Text('${photo.data["quote"]["stats"]["latestPrice"] ?? ""}')
),
],
),
)
.toList())
),
),
);
}
问题是值存在，并且在控制台中输出时Flutter说为空。
The issue is that values are there and Flutter says is null when the output is in the console.
===================
Launching lib/main.dart on iPhone 11 Pro Max in debug mode...
Running Xcode build...
Xcode build done. 17.9s
Waiting for iPhone 11 Pro Max to report its views...
Debug service listening on ws://127.0.0.1:57768/yyPV-GQyldg=/ws
Syncing files to device iPhone 11 Pro Max...
flutter: {"PGX":{"stats":{"week52change":-0.025465,"week52high":15.28,"week52low":9.71,"marketcap":4595628000,"employees":null,"day200MovingAvg":14.55,"day50MovingAvg":13.39,"float":null,"avg10Volume":2336007.5,"avg30Volume":2648722.77,"ttmEPS":null,"ttmDividendRate":0.8361,"companyName":"Invesco Preferred ETF","sharesOutstanding":324550000,"maxChangePercent":-0.3042,"year5ChangePercent":-0.0367,"year2ChangePercent":-0.0167,"year1ChangePercent":-0.025465,"ytdChangePercent":-0.064111,"month6ChangePercent":-0.045822,"month3ChangePercent":-0.052209,"month1ChangePercent":0.019438,"day30ChangePercent":0.028322,"day5ChangePercent":0.015054,"nextDividendDate":"2020-05-18","dividendYield":0.059046610169491524,"nextEarningsDate":null,"exDividendDate":"2020-05-18","peRatio":null,"beta":0.5684535732534528},"quote":{"symbol":"PGX","companyName":"Invesco Preferred ETF","primaryExchange":"NYSE Arca","calculationPrice":"close","open":14.11,"openTime":1590154200191,"openSource":"official","close":14.16,"closeT<…>
flutter: 2020","latestUpdate":1590177600180,"latestVolume":4747,"iexRealtimePrice":null,"iexRealtimeSize":null,"iexLastUpdated":null,"delayedPrice":11.245,"delayedPriceTime":1590192000004,"oddLotDelayedPrice":11.193,"oddLotDelayedPriceTime":1590173727614,"extendedPrice":11.245,"extendedChange":0.005,"extendedChangePercent":0.00044,"extendedPriceTime":1590186600005,"previousClose":11.16,"previousVolume":8688,"change":0.08,"changePercent":0.00717,"volume":4747,"iexMarketPercent":null,"iexVolume":null,"avgTotalVolume":12262,"iexBidPrice":null,"iexBidSize":null,"iexAskPrice":null,"iexAskSize":null,"iexOpen":null,"iexOpenTime":null,"iexClose":11.04,"iexCloseTime":1589988569572,"marketCap":35406000,"peRatio":null,"week52High":16.6,"week52Low":8.47,"ytdChange":-0.300712,"lastTradeTime":1590177600181,"isUSMarketOpen":false}},"IPFF":{"stats":{"week52change":-0.23383400000000001,"week52high":15.71,"week52low":8.38,"marketcap":28738500,"employees":null,"day200MovingAvg":13.89,"day50MovingAvg":10.96,"float<…>
flutter: 95
flutter: {"PGX":{"stats":{"week52change":-0.025465,"week52high":15.28,"week52low":9.71,"marketcap":4595628000,"employees":null,"day200MovingAvg":14.55,"day50MovingAvg":13.39,"float":null,"avg10Volume":2336007.5,"avg30Volume":2648722.77,"ttmEPS":null,"ttmDividendRate":0.8361,"companyName":"Invesco Preferred ETF","sharesOutstanding":324550000,"maxChangePercent":-0.3042,"year5ChangePercent":-0.0367,"year2ChangePercent":-0.0167,"year1ChangePercent":-0.025465,"ytdChangePercent":-0.064111,"month6ChangePercent":-0.045822,"month3ChangePercent":-0.052209,"month1ChangePercent":0.019438,"day30ChangePercent":0.028322,"day5ChangePercent":0.015054,"nextDividendDate":"2020-05-18","dividendYield":0.059046610169491524,"nextEarningsDate":null,"exDividendDate":"2020-05-18","peRatio":null,"beta":0.5684535732534528},"**quote":{"symbol":"PGX","companyName":"Invesco Preferred ETF","primaryExchange":"NYSE Arca","calculationPrice":"close","open":14.11,"openTime":1590154200191,"openSource":"official","close":14.16,"closeT<…>
flutter: 2020","latestUpdate":1590177600180,"latestVolume":4747,"iexRealtimePrice":null,"iexRealtimeSize":null,"iexLastUpdated":null,"delayedPrice":11.245,"delayedPriceTime":1590192000004,"oddLotDelayedPrice":11.193,"oddLotDelayedPriceTime":1590173727614,"extendedPrice":11.245,"extendedChange":0.005,"extendedChangePercent":0.00044,"extendedPriceTime":1590186600005,"previousClose":11.16,"previousVolume":8688,"change":0.08,"changePercent":0.00717,"volume":4747,"iexMarketPercent":null,"iexVolume":null,"avgTotalVolume":12262,"iexBidPrice":null,"iexBidSize":null,"iexAskPrice":null,"iexAskSize":null,"iexOpen":null,"iexOpenTime":null,"iexClose":11.04,"iexCloseTime":1589988569572,"marketCap":35406000,"peRatio":null,"week52High":16.6,"week52Low":8.47,"ytdChange":-0.300712,"lastTradeTime":1590177600181,"isUSMarketOpen":false}},"IPFF":{"stats":{"week52change":-0.23383400000000001,"week52high":15.71,"week52low":8.38,"marketcap":28738500,"employees":null,"day200MovingAvg":13.89,"day50MovingAvg":10.96,"float<…>
flutter: 95**
════════ Exception caught by widgets library ═══════════════════════════════════════════════════════
The following NoSuchMethodError was thrown building photorealist(dirty, state: _PhotosListState#8eef8):
The method '[]' was called on null.
Receiver: null
Tried calling: []("iexClose")
=============
列价格为空。
如果我尝试调用 delayedPrice：11.552， 或 iexClose：11.04。，它不会在应用程序中打印。
< a href = https://i.stack.imgur.com/u6uYS.png rel = nofollow noreferrer>
============= Column Price is empty. If I try to call "delayedPrice":11.552," or "iexClose":11.04. it does not print in the app.
推荐答案
在响应中，对于某些公司（或符号）， quote 的值为 null 。
In the response, for some companies (or symbol) the quote value is null.
示例（IEMF，欧盟，等等）
Example(IEMF, EU, etc):
"IEMF": {
"stats": {
"symbol": "IEMF",
"nextDividendDate": null,
"nextEarningsDate": null,
"exDividendDate": null,
"peRatio": null,
"beta": null
},
"quote": null
},
"EU": {
"stats": {
"symbol": "EU",
"nextDividendDate": null,
"nextEarningsDate": null,
"exDividendDate": null,
"peRatio": null,
"beta": null
},
"quote": null
},
检查：
photo.data [ quote]！=空
photo.data["quote"] != null
在报价内没有统计信息。所以不要调用 photo.data [ quote] [ stats]
And there is no stats inside quote. so don't call photo.data["quote"]["stats"]
而不是 Text（'$ {photo.data [ quote] [ stats] [ latestPrice] ??}'），使用 Text （'$ {（photo.data [ quote]！= null？photo.data [ quote] [ latestPrice]：）??}'）
完整代码：
import 'dart:async';
import 'dart:convert';
import 'package:flutter/foundation.dart';
import 'package:flutter/material.dart';
import 'package:http/http.dart' as http;
//import 'package:flutter_web/material.dart';
//import 'package:flutter/main.dart' as app;
//import 'package:flutter_web_ui/ui.dart' as ui;
Future<List<Photo>> fetchPhotos(http.Client client) async {
final response =
// await client.get('https://cloud.iexapis.com/stable/stock/market/batch?symbols=CNPF,ICOL,PGX,MORL,EMLC,GYLD,IPFF,SMB,YDIV,YYY,PEY,IEI,TLH,DIA,BSJF,MONY&types=quote,stats&token=');
await client.get(
'https://cloud.iexapis.com/stable/stock/market/batch?symbols=PGX,MORL,EMLC,GYLD,IPFF,SMB,YDIV,YYY,PEY,PGF,SNLN,DVHL,AUNZ,MDIV,PHB,PFXF,FPE,TIPX,MLN,SDIV,SIPE,SEMF,EMAG,IEMF,EU,BSCM,LEMF,BSCL,BSCK,BSCJ,BSCI,DSUM,BSCF,KBWD,PCEF,BSCG,BSCH,HYEM,ITM,BKLN,PGHY,IBCE,PZT,IJNK,XMPT,THHY,QYLD,IHY,IYLD,SHYD,PRB,DVHI,GOVT,BSJJ,BSJK,RIGS,INY,IBCD,PZA,PFIG,IBCC,BSCE,PVI,MBG,CXA,FWDB,DIV,CHLC,BSJI,FLTR,PWZ,MUAH,IBDD,PICB,IBDB,BSJH,RVNU,BSJG,IBDC,XOVR,BSJE,EBND,PCY,BWX,SJNK,DES,ANGL,BAB,SST,EMCD,CBND,HYD,PLW,SCPB,FLRN,BWZ,KBWY,ELD,IBND,AOK,RWXL,ITR,DON,DGRS,JNK,TZD,EPU,PFF,HYLD,GGOV,ULST,SPHD,HFIN,DGRW,LWC,ALD,LEMB,AGND,ITIP,EMHY,QLTC,TFI,SRLN,HYLS,SHM,GNMA,CEMB,IGOV,MINC,AGZD,FTSL,SPLV,GHYG,ISTB,ENGN,CMBS,GTIP,SCHO,SMMU,QLTA,SCHZ,HSPX,TUZ,GIY,GSY,TFLO,VMBS,CWB,FLOT,STPZ,MUAC,SCHR,BABZ,HYXU,GMTB,MUNI,WIP,MUAD,QLTB,SCHP,GMMB,MUAE,IPE,NYF,BNDX,MUAF,HYMB,TIPZ,CMF,LAG,ILTB,ITE,CLY,VGSH,VGIT,LTPZ,BABS,HYHG,EMCB,DVYL,VGLT,DHS,TLO,VWOB,IGHG,GLCB,RAVI,VCSH,BSV,BND,BIV,ISHG,SDYL,VCIT,SHY,BLV,HYG,VCLT,TENZ,DTN,BIL,AUD,DLN,DTD,FTSD,CAD,STIP,CORP,HYS,HOLD,TRSY,IEF,IBDA,COBO,BOND,MINT,MBB,CSJ,AGG,SUB,EMB,CIU,GVI,MUB,GBF,TIP,AGZ,CFT,LQD,TLT,IEI,TLH,DIA,BSJF,MONY&types=stats,quote&token=pk_fd71da12cae34ae9abdf3df4958302fe',
);
//https://cloud.iexapis.com/v1/stock/market/batch?&types=price&symbols=aapl,fb,tsla&token=YOUR_TOKEN_HERE
//https://cloud.iexapis.com/v1/stock/market/batch?&types=quote&symbols=aapl,fb,tsla&token=
// Use the compute function to run parsePhotos in a separate isolate.
//https://cloud.iexapis.com/stable/stock/market/batch?symbols=CNPF,ICOL,PGX,MORL,EMLC,GYLD,IPFF,SMB,YDIV,YYY,PEY,PGF,SNLN,DVHL,AUNZ,MDIV,PHB,PFXF,FPE,TIPX,MLN,SDIV,SIPE,SEMF,EMAG,IEMF,EU,BSCM,LEMF,BSCL,BSCK,BSCJ,BSCI,DSUM,BSCF,KBWD,PCEF,BSCG,BSCH,HYEM,ITM,BKLN,PGHY,IBCE,PZT,IJNK,XMPT,THHY,QYLD,IHY,IYLD,SHYD,PRB,DVHI,GOVT,BSJJ,BSJK,RIGS,INY,IBCD,PZA,PFIG,IBCC,BSCE,PVI,MBG,CXA,FWDB,DIV,CHLC,BSJI,FLTR,PWZ,MUAH,IBDD,PICB,IBDB,BSJH,RVNU,BSJG,IBDC,XOVR,BSJE,EBND,PCY,BWX,SJNK,DES,ANGL,BAB,SST,EMCD,CBND,HYD,PLW,SCPB,FLRN,BWZ,KBWY,ELD,IBND,AOK,RWXL,ITR,DON,DGRS,JNK,TZD,EPU,PFF,HYLD,GGOV,ULST,SPHD,HFIN,DGRW,LWC,ALD,LEMB,AGND,ITIP,EMHY,QLTC,TFI,SRLN,HYLS,SHM,GNMA,CEMB,IGOV,MINC,AGZD,FTSL,SPLV,GHYG,ISTB,ENGN,CMBS,GTIP,SCHO,SMMU,QLTA,SCHZ,HSPX,TUZ,GIY,GSY,TFLO,VMBS,CWB,FLOT,STPZ,MUAC,SCHR,BABZ,HYXU,GMTB,MUNI,WIP,MUAD,QLTB,SCHP,GMMB,MUAE,IPE,NYF,BNDX,MUAF,HYMB,TIPZ,CMF,LAG,ILTB,ITE,CLY,VGSH,VGIT,LTPZ,BABS,HYHG,EMCB,DVYL,VGLT,DHS,TLO,VWOB,IGHG,GLCB,RAVI,VCSH,BSV,BND,BIV,ISHG,SDYL,VCIT,SHY,BLV,HYG,VCLT,TENZ,DTN,BIL,AUD,DLN,DTD,FTSD,CAD,STIP,CORP,HYS,HOLD,TRSY,IEF,IBDA,COBO,BOND,MINT,MBB,CSJ,AGG,SUB,EMB,CIU,GVI,MUB,GBF,TIP,AGZ,CFT,LQD,TLT,IEI,TLH,DIA,BSJF,MONY&types=quote,stats&token=
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);
debugPrint(responseBody, wrapWidth: 1000);
print(obj.length);
List<Photo> photoList = [];
obj.forEach((k, v) => photoList.add(Photo(k, v)));
return photoList;
}
class Photo {
String symbol;
//String companyName;
dynamic data;
// dynamic iexClose;
// dynamic quote;
Photo(this.symbol, this.data);
}
void main() => runApp(MyApp());
class MyApp extends StatelessWidget {
@override
Widget build(BuildContext context) {
final appTitle = 'Monthly Paying ETFs';
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(
drawer: Drawer(
// Add a ListView to the drawer. This ensures the user can scroll
// through the options in the drawer if there isn't enough vertical
// space to fit everything.
child: ListView(
// Important: Remove any padding from the ListView.
padding: EdgeInsets.zero,
children: <Widget>[
DrawerHeader(
child: Text('About'),
decoration: BoxDecoration(
color: Colors.grey,
),
),
ListTile(
title: Text(
'This app is to provide the list of ETF s that pay monthly dividend',
),
onTap: () {
// Update the state of the app
// ...
// Then close the drawer
Navigator.pop(context);
},
),
ListTile(
title: Text(
'for questions or feedback please contact me at ',
),
onTap: () {
// Update the state of the app
// ...
// Then close the drawer
Navigator.pop(context);
},
),
],
),
),
appBar: AppBar(
title: Text(title),
backgroundColor: Colors.greenAccent,
),
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 StatefulWidget {
final List photos;
PhotosList({Key key, this.photos})
: assert(photos != null),
super(key: key);
@override
_PhotosListState createState() => _PhotosListState();
}
class _PhotosListState extends State<PhotosList> {
@override
Widget build(BuildContext context) {
return bodyData();
}
SingleChildScrollView bodyData() => SingleChildScrollView(
scrollDirection: Axis.vertical,
// padding: EdgeInsets.all(0.0),
//padding: const EdgeInsets.symmetric(
// padding: new EdgeInsets.fromLTRB(0.001, .001, 1.0, 1.0),
padding: EdgeInsets.all(0.05),
// child: FittedBox(fit:BoxFit.contain,
child: SingleChildScrollView(
scrollDirection: Axis.horizontal,
child: FittedBox(
fit: BoxFit.fitHeight,
child: DataTable(
// sortColumnIndex: 1,
// sortAscending: true,
columns: <DataColumn>[
DataColumn(
label: Text("Company"),
onSort: (_, __) {
setState(() {
widget.photos.sort((a, b) => a.data["quote"]
["companyName"]
.compareTo(b.data["quote"]["companyName"]));
});
},
),
DataColumn(
label: Text("ttmDivRate"),
numeric: true,
onSort: (_, __) {
setState(() {
widget.photos.sort((a, b) => a.data["quote"]
["ttmDividendRate"]
.compareTo(b.data["quote"]["ttmDividendRate"]));
});
},
),
DataColumn(
label: Text("Price"),
numeric: true,
onSort: (_, __) {
setState(() {
widget.photos.sort((a, b) => a.data["quote"]
["latestPrice"]
.compareTo(b.data["quote"]["latestPrice"]));
});
},
),
],
rows: widget.photos
.map(
(photo) => DataRow(
cells: [
DataCell(
Text(
'${photo.data["stats"]["companyName"] ?? ""}',
),
),
DataCell(
Text(
'${photo.data["stats"]["ttmDividendRate"] ?? ""}',
),
),
//["quote"]["stats"]
DataCell(
Text(
'${(photo.data["quote"] != null ? photo.data["quote"]["latestPrice"] : "") ?? ""}',
),
),
],
),
)
.toList(),
),
),
),
);
}
这篇关于方法'[]'在null上被调用。接收者：null的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！
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