如何在 Flutter 中使用 CoinMarketCap API

Posted 2023-02-23

【中文标题】如何在 Flutter 中使用 CoinMarketCap API

【英文标题】：How to use CoinMarketCap API in flutter

【发布时间】：2020-09-19 06:16:00

【问题描述】：

我正在关注一个显示加密货币价格的应用教程，但我在使用新 API 时遇到了问题。下面的代码只是来自教程，导师使用的是旧的 coinmarketcap API。 Coinmarketcap 已迁移到新的，您需要注册以获得免费的 API 密钥。新 API 的文档：https://coinmarketcap.com/api/documentation/v1。

我想我需要将 _apiURL 更改为 https://pro-api.coinmarketcap.com/v1/cryptocurrency/listings/latest?start=1&limit=5000&convert=USD 并以某种方式使用 APIKey。有没有人有办法解决吗？对颤振和 API 来说还是有点新，所以如果这个问题很难回答，我很抱歉。

Future<void> getCryptoPrices() async 
//async to use await, which suspends the current function, while it does other stuff and resumes when data ready
print('getting crypto prices'); //print
String _apiURL =
    "https://api.coinmarketcap.com/v1/ticker/"; //url to get data
setState(() 
  this._loading = true; //before calling the api, set the loading to true
);
http.Response response = await http.get(_apiURL); //waits for response
setState(() 
  this._cryptoList =
      jsonDecode(response.body); //sets the state of our widget
  this._loading = false; //set the loading to false after we get a response
  print(_cryptoList); //prints the list
);
return;  

【参考方案1】：

您可以在下面复制粘贴运行完整代码并在运行前替换your-key 您可以将API key 放入headers 并使用payloadFromJson 解析json 响应并使用FutureBuilder 显示 您可以在完整代码中查看 Payload 类定义

Future<Payload> getCryptoPrices() async 
    var response = await http.get(
        "https://pro-api.coinmarketcap.com/v1/cryptocurrency/listings/latest?start=1&limit=5000&convert=USD",
        headers: 
          'X-CMC_PRO_API_KEY': 'your-key',
          "Accept": "application/json",
        );

    if (response.statusCode == 200) 
      return payloadFromJson(response.body);
    
  

工作演示

完整代码

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

Payload payloadFromJson(String str) => Payload.fromJson(json.decode(str));

String payloadToJson(Payload data) => json.encode(data.toJson());

class Payload 
  Payload(
    this.status,
    this.data,
  );

  Status status;
  List<Datum> data;

  factory Payload.fromJson(Map<String, dynamic> json) => Payload(
        status: Status.fromJson(json["status"]),
        data: List<Datum>.from(json["data"].map((x) => Datum.fromJson(x))),
      );

  Map<String, dynamic> toJson() => 
        "status": status.toJson(),
        "data": List<dynamic>.from(data.map((x) => x.toJson())),
      ;


class Datum 
  Datum(
    this.id,
    this.name,
    this.symbol,
    this.slug,
    this.numMarketPairs,
    this.dateAdded,
    this.tags,
    this.maxSupply,
    this.circulatingSupply,
    this.totalSupply,
    this.platform,
    this.cmcRank,
    this.lastUpdated,
    this.quote,
  );

  int id;
  String name;
  String symbol;
  String slug;
  int numMarketPairs;
  DateTime dateAdded;
  List<Tag> tags;
  double maxSupply;
  double circulatingSupply;
  double totalSupply;
  Platform platform;
  int cmcRank;
  DateTime lastUpdated;
  Quote quote;

  factory Datum.fromJson(Map<String, dynamic> json) => Datum(
        id: json["id"],
        name: json["name"],
        symbol: json["symbol"],
        slug: json["slug"],
        numMarketPairs: json["num_market_pairs"],
        dateAdded: DateTime.parse(json["date_added"]),
        tags: List<Tag>.from(json["tags"].map((x) => tagValues.map[x])),
        maxSupply:
            json["max_supply"] == null ? null : json["max_supply"].toDouble(),
        circulatingSupply: json["circulating_supply"] == null
            ? null
            : json["circulating_supply"].toDouble(),
        totalSupply: json["total_supply"] == null
            ? null
            : json["total_supply"].toDouble(),
        platform: json["platform"] == null
            ? null
            : Platform.fromJson(json["platform"]),
        cmcRank: json["cmc_rank"],
        lastUpdated: DateTime.parse(json["last_updated"]),
        quote: Quote.fromJson(json["quote"]),
      );

  Map<String, dynamic> toJson() => 
        "id": id,
        "name": name,
        "symbol": symbol,
        "slug": slug,
        "num_market_pairs": numMarketPairs,
        "date_added": dateAdded.toIso8601String(),
        "tags": List<dynamic>.from(tags.map((x) => tagValues.reverse[x])),
        "max_supply": maxSupply == null ? null : maxSupply,
        "circulating_supply":
            circulatingSupply == null ? null : circulatingSupply,
        "total_supply": totalSupply == null ? null : totalSupply,
        "platform": platform == null ? null : platform.toJson(),
        "cmc_rank": cmcRank,
        "last_updated": lastUpdated.toIso8601String(),
        "quote": quote.toJson(),
      ;


class Platform 
  Platform(
    this.id,
    this.name,
    this.symbol,
    this.slug,
    this.tokenAddress,
  );

  int id;
  Name name;
  Symbol symbol;
  Slug slug;
  String tokenAddress;

  factory Platform.fromJson(Map<String, dynamic> json) => Platform(
        id: json["id"],
        name: nameValues.map[json["name"]],
        symbol: symbolValues.map[json["symbol"]],
        slug: slugValues.map[json["slug"]],
        tokenAddress: json["token_address"],
      );

  Map<String, dynamic> toJson() => 
        "id": id,
        "name": nameValues.reverse[name],
        "symbol": symbolValues.reverse[symbol],
        "slug": slugValues.reverse[slug],
        "token_address": tokenAddress,
      ;


enum Name 
  ETHEREUM,
  TRON,
  OMNI,
  RSK_SMART_BITCOIN,
  BINANCE_COIN,
  STELLAR,
  NEO,
  V_SYSTEMS,
  ARDOR,
  QTUM,
  XRP,
  WAVES,
  ONTOLOGY,
  EOS,
  NEBULAS,
  NEM,
  BIT_SHARES,
  BITCOIN_CASH,
  INT_CHAIN,
  COSMOS,
  UBIQ,
  VE_CHAIN,
  NU_BITS,
  PIVX,
  COUNTERPARTY,
  KOMODO,
  ICON,
  GX_CHAIN,
  VITE,
  WANCHAIN,
  iosT,
  TRUE_CHAIN,
  ETHEREUM_CLASSIC


final nameValues = EnumValues(
  "Ardor": Name.ARDOR,
  "Binance Coin": Name.BINANCE_COIN,
  "Bitcoin Cash": Name.BITCOIN_CASH,
  "BitShares": Name.BIT_SHARES,
  "Cosmos": Name.COSMOS,
  "Counterparty": Name.COUNTERPARTY,
  "EOS": Name.EOS,
  "Ethereum": Name.ETHEREUM,
  "Ethereum Classic": Name.ETHEREUM_CLASSIC,
  "GXChain": Name.GX_CHAIN,
  "ICON": Name.ICON,
  "INT Chain": Name.INT_CHAIN,
  "IOST": Name.IOST,
  "Komodo": Name.KOMODO,
  "Nebulas": Name.NEBULAS,
  "NEM": Name.NEM,
  "Neo": Name.NEO,
  "NuBits": Name.NU_BITS,
  "Omni": Name.OMNI,
  "Ontology": Name.ONTOLOGY,
  "PIVX": Name.PIVX,
  "Qtum": Name.QTUM,
  "RSK Smart Bitcoin": Name.RSK_SMART_BITCOIN,
  "Stellar": Name.STELLAR,
  "TRON": Name.TRON,
  "TrueChain": Name.TRUE_CHAIN,
  "Ubiq": Name.UBIQ,
  "VeChain": Name.VE_CHAIN,
  "VITE": Name.VITE,
  "v.systems": Name.V_SYSTEMS,
  "Wanchain": Name.WANCHAIN,
  "Waves": Name.WAVES,
  "XRP": Name.XRP
);

enum Slug 
  ETHEREUM,
  TRON,
  OMNI,
  RSK_SMART_BITCOIN,
  BINANCE_COIN,
  STELLAR,
  NEO,
  V_SYSTEMS,
  ARDOR,
  QTUM,
  XRP,
  WAVES,
  ONTOLOGY,
  EOS,
  NEBULAS_TOKEN,
  NEM,
  BITSHARES,
  BITCOIN_CASH,
  INT_CHAIN,
  COSMOS,
  UBIQ,
  VECHAIN,
  NUBITS,
  PIVX,
  COUNTERPARTY,
  KOMODO,
  ICON,
  GXCHAIN,
  VITE,
  WANCHAIN,
  IOSTOKEN,
  TRUECHAIN,
  ETHEREUM_CLASSIC


final slugValues = EnumValues(
  "ardor": Slug.ARDOR,
  "binance-coin": Slug.BINANCE_COIN,
  "bitcoin-cash": Slug.BITCOIN_CASH,
  "bitshares": Slug.BITSHARES,
  "cosmos": Slug.COSMOS,
  "counterparty": Slug.COUNTERPARTY,
  "eos": Slug.EOS,
  "ethereum": Slug.ETHEREUM,
  "ethereum-classic": Slug.ETHEREUM_CLASSIC,
  "gxchain": Slug.GXCHAIN,
  "icon": Slug.ICON,
  "int-chain": Slug.INT_CHAIN,
  "iostoken": Slug.IOSTOKEN,
  "komodo": Slug.KOMODO,
  "nebulas-token": Slug.NEBULAS_TOKEN,
  "nem": Slug.NEM,
  "neo": Slug.NEO,
  "nubits": Slug.NUBITS,
  "omni": Slug.OMNI,
  "ontology": Slug.ONTOLOGY,
  "pivx": Slug.PIVX,
  "qtum": Slug.QTUM,
  "rsk-smart-bitcoin": Slug.RSK_SMART_BITCOIN,
  "stellar": Slug.STELLAR,
  "tron": Slug.TRON,
  "truechain": Slug.TRUECHAIN,
  "ubiq": Slug.UBIQ,
  "vechain": Slug.VECHAIN,
  "vite": Slug.VITE,
  "v-systems": Slug.V_SYSTEMS,
  "wanchain": Slug.WANCHAIN,
  "waves": Slug.WAVES,
  "xrp": Slug.XRP
);

enum Symbol 
  ETH,
  TRX,
  OMNI,
  RBTC,
  BNB,
  XLM,
  NEO,
  VSYS,
  ARDR,
  QTUM,
  XRP,
  WAVES,
  ONT,
  EOS,
  NAS,
  XEM,
  BTS,
  BCH,
  INT,
  ATOM,
  UBQ,
  VET,
  USNBT,
  PIVX,
  XCP,
  KMD,
  ICX,
  GXC,
  VITE,
  WAN,
  IOST,
  TRUE,
  ETC


final symbolValues = EnumValues(
  "ARDR": Symbol.ARDR,
  "ATOM": Symbol.ATOM,
  "BCH": Symbol.BCH,
  "BNB": Symbol.BNB,
  "BTS": Symbol.BTS,
  "EOS": Symbol.EOS,
  "ETC": Symbol.ETC,
  "ETH": Symbol.ETH,
  "GXC": Symbol.GXC,
  "ICX": Symbol.ICX,
  "INT": Symbol.INT,
  "IOST": Symbol.IOST,
  "KMD": Symbol.KMD,
  "NAS": Symbol.NAS,
  "NEO": Symbol.NEO,
  "OMNI": Symbol.OMNI,
  "ONT": Symbol.ONT,
  "PIVX": Symbol.PIVX,
  "QTUM": Symbol.QTUM,
  "RBTC": Symbol.RBTC,
  "TRUE": Symbol.TRUE,
  "TRX": Symbol.TRX,
  "UBQ": Symbol.UBQ,
  "USNBT": Symbol.USNBT,
  "VET": Symbol.VET,
  "VITE": Symbol.VITE,
  "VSYS": Symbol.VSYS,
  "WAN": Symbol.WAN,
  "WAVES": Symbol.WAVES,
  "XCP": Symbol.XCP,
  "XEM": Symbol.XEM,
  "XLM": Symbol.XLM,
  "XRP": Symbol.XRP
);

class Quote 
  Quote(
    this.usd,
  );

  Usd usd;

  factory Quote.fromJson(Map<String, dynamic> json) => Quote(
        usd: Usd.fromJson(json["USD"]),
      );

  Map<String, dynamic> toJson() => 
        "USD": usd.toJson(),
      ;


class Usd 
  Usd(
    this.price,
    this.volume24H,
    this.percentChange1H,
    this.percentChange24H,
    this.percentChange7D,
    this.marketCap,
    this.lastUpdated,
  );

  double price;
  double volume24H;
  double percentChange1H;
  double percentChange24H;
  double percentChange7D;
  double marketCap;
  DateTime lastUpdated;

  factory Usd.fromJson(Map<String, dynamic> json) => Usd(
        price: json["price"] == null ? null : json["price"].toDouble(),
        volume24H:
            json["volume_24h"] == null ? null : json["volume_24h"].toDouble(),
        percentChange1H: json["percent_change_1h"] == null
            ? null
            : json["percent_change_1h"].toDouble(),
        percentChange24H: json["percent_change_24h"] == null
            ? null
            : json["percent_change_24h"].toDouble(),
        percentChange7D: json["percent_change_7d"] == null
            ? null
            : json["percent_change_7d"].toDouble(),
        marketCap:
            json["market_cap"] == null ? null : json["market_cap"].toDouble(),
        lastUpdated: DateTime.parse(json["last_updated"]),
      );

  Map<String, dynamic> toJson() => 
        "price": price == null ? null : price,
        "volume_24h": volume24H == null ? null : volume24H,
        "percent_change_1h": percentChange1H == null ? null : percentChange1H,
        "percent_change_24h":
            percentChange24H == null ? null : percentChange24H,
        "percent_change_7d": percentChange7D == null ? null : percentChange7D,
        "market_cap": marketCap == null ? null : marketCap,
        "last_updated": lastUpdated.toIso8601String(),
      ;


enum Tag  MINEABLE 

final tagValues = EnumValues("mineable": Tag.MINEABLE);

class Status 
  Status(
    this.timestamp,
    this.errorCode,
    this.errorMessage,
    this.elapsed,
    this.creditCount,
    this.notice,
  );

  DateTime timestamp;
  int errorCode;
  dynamic errorMessage;
  int elapsed;
  int creditCount;
  dynamic notice;

  factory Status.fromJson(Map<String, dynamic> json) => Status(
        timestamp: DateTime.parse(json["timestamp"]),
        errorCode: json["error_code"],
        errorMessage: json["error_message"],
        elapsed: json["elapsed"],
        creditCount: json["credit_count"],
        notice: json["notice"],
      );

  Map<String, dynamic> toJson() => 
        "timestamp": timestamp.toIso8601String(),
        "error_code": errorCode,
        "error_message": errorMessage,
        "elapsed": elapsed,
        "credit_count": creditCount,
        "notice": notice,
      ;


class EnumValues<T> 
  Map<String, T> map;
  Map<T, String> reverseMap;

  EnumValues(this.map);

  Map<T, String> get reverse 
    if (reverseMap == null) 
      reverseMap = map.map((k, v) => new MapEntry(v, k));
    
    return reverseMap;
  


void main() 
  runApp(MyApp());


class MyApp extends StatelessWidget 
  @override
  Widget build(BuildContext context) 
    return MaterialApp(
      title: 'Flutter Demo',
      theme: ThemeData(
        primarySwatch: Colors.blue,
        visualDensity: VisualDensity.adaptivePlatformDensity,
      ),
      home: MyHomePage(title: 'Flutter Demo Home Page'),
    );
  


class MyHomePage extends StatefulWidget 
  MyHomePage(Key key, this.title) : super(key: key);

  final String title;

  @override
  _MyHomePageState createState() => _MyHomePageState();


class _MyHomePageState extends State<MyHomePage> 
  int _counter = 0;
  Future<Payload> _future;

  Future<Payload> getCryptoPrices() async 
    var response = await http.get(
        "https://pro-api.coinmarketcap.com/v1/cryptocurrency/listings/latest?start=1&limit=5000&convert=USD",
        headers: 
          'X-CMC_PRO_API_KEY': 'your-key',
          "Accept": "application/json",
        );

    if (response.statusCode == 200) 
      return payloadFromJson(response.body);
    
  

  @override
  void initState() 
    // TODO: implement initState
    super.initState();
    _future = getCryptoPrices();
  

  @override
  Widget build(BuildContext context) 
    return Scaffold(
        appBar: AppBar(
          title: Text(widget.title),
        ),
        body: FutureBuilder(
            future: _future,
            builder: (context, AsyncSnapshot<Payload> snapshot) 
              switch (snapshot.connectionState) 
                case ConnectionState.none:
                  return Text('none');
                case ConnectionState.waiting:
                  return Center(child: CircularProgressIndicator());
                case ConnectionState.active:
                  return Text('');
                case ConnectionState.done:
                  if (snapshot.hasError) 
                    return Text(
                      '$snapshot.error',
                      style: TextStyle(color: Colors.red),
                    );
                   else 
                    return ListView.builder(
                        itemCount: snapshot.data.data.length,
                        itemBuilder: (context, index) 
                          return Card(
                              elevation: 6.0,
                              child: Padding(
                                padding: const EdgeInsets.only(
                                    top: 6.0,
                                    bottom: 6.0,
                                    left: 8.0,
                                    right: 8.0),
                                child: Row(
                                  crossAxisAlignment: CrossAxisAlignment.start,
                                  children: <Widget>[
                                    Text(snapshot.data.data[index].name),
                                    Spacer(),
                                    Text(snapshot.data.data[index].lastUpdated
                                        .toIso8601String()),
                                    Spacer(),
                                    Text(
                                      snapshot.data.data[index].quote.usd.price
                                          .toString(),
                                    ),
                                  ],
                                ),
                              ));
                        );
                  
              
            ));
  

【讨论】：

从 API 中获取徽标是否也很困难？

我在 API 响应中没有看到徽标字段名称。是 png 还是 jpeg。

coinmarketcap.com/api/documentation/v1/#operation/…。 “徽标”下的 PNG。