json - Flutter从互联网上获取数据

Question

我正在尝试从here获取一些信息，例如名称， avatar_url ， stargazers_count 和说明

{
  "total_count": 18689015,
  "incomplete_results": true,
  "items": [
    {
      "id": 215415332,
      "node_id": "MDEwOlJlcG9zaXRvcnkyMTU0MTUzMzI=",
      "name": "HackingNeuralNetworks",
      "full_name": "Kayzaks/HackingNeuralNetworks",
      "private": false,
      "owner": {
        "login": "Kayzaks",
        "id": 11071537,
        "node_id": "MDQ6VXNlcjExMDcxNTM3",
        "avatar_url": "https://avatars1.githubusercontent.com/u/11071537?v=4",
        "gravatar_id": "",
        "url": "https://api.github.com/users/Kayzaks",
        "html_url": "https://github.com/Kayzaks",
        "followers_url": "https://api.github.com/users/Kayzaks/followers",
        "following_url": "https://api.github.com/users/Kayzaks/following{/other_user}",
        "gists_url": "https://api.github.com/users/Kayzaks/gists{/gist_id}",
        "starred_url": "https://api.github.com/users/Kayzaks/starred{/owner}{/repo}",
        "subscriptions_url": "https://api.github.com/users/Kayzaks/subscriptions",
        "organizations_url": "https://api.github.com/users/Kayzaks/orgs",
        "repos_url": "https://api.github.com/users/Kayzaks/repos",
        "events_url": "https://api.github.com/users/Kayzaks/events{/privacy}",
        "received_events_url": "https://api.github.com/users/Kayzaks/received_events",
        "type": "User",
        "site_admin": false
      },
      "html_url": "https://github.com/Kayzaks/HackingNeuralNetworks",
      "description": "A small course on exploiting and defending neural networks",
      "fork": false, 
    ....
    ....

在运行时，我收到此消息错误:

type _internalLine HashMap<String , dynamic> is not a subtype of type List<dynamic> in type cast

这是完整的代码:

RepoItem:

class RepoItem {
  Owner owner;
  String name;
  String stargazers_count;
  String description;

  RepoItem._({this.owner, this.name, this.stargazers_count, this.description});

  factory RepoItem.fromJson(Map<String, dynamic> json) {
    return new RepoItem._(
        owner: json['owner'],
        name: json['name'],
        stargazers_count: json['stargazers_count'],
        description: json['description']);
  }
}

PageState:

class _MyHomePageState extends State<MyHomePage> {
  List<RepoItem> list = List();
  var isLoading = false;

  Future<List<RepoItem>> _fetchData() async {
    final response = await http.get(
        "https://api.github.com/search/repositories?q=created:%3E2018-10-22&sort=stars&order=desc");
    list = (json.decode(response.body) as List)
        .map((data) => new RepoItem.fromJson(data.body))
        .toList();
    return list;
  }

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: Text(widget.title),
      ),
      body: Container(
        child: FutureBuilder(
          future: _fetchData(),
          builder: (BuildContext context, AsyncSnapshot asyncSnapshot) {
            if (asyncSnapshot.hasError) {
              return Container(
                child: Center(
                  child: Text(asyncSnapshot.error.toString()),
                ),
              );
            }
            if (asyncSnapshot.data == null) {
              return Container(
                child: Center(
                  child: Text("Loading ..."),
                ),
              );
            } else {
              return ListView.builder(
                itemCount: asyncSnapshot.data.length,
                itemBuilder: (BuildContext context, int index) {
                  return ListTile(
                    title: Text(asyncSnapshot.data[index].name),
                    leading: CircleAvatar(
                      backgroundImage: NetworkImage(
                          asyncSnapshot.data[index].owner.avatar_url),
                    ),
                    subtitle: Text(asyncSnapshot.data[index].description),
                  );
                },
              );
            }
          },
        ),
      ),
    );
  }
}

Answer 1

您可以在下面复制粘贴运行完整代码
您可以使用payloadFromJson进行解析，可以看到完整代码中的Payload类

Payload payloadFromJson(String str) => Payload.fromJson(json.decode(str));
... 
var items = snapshot.data.items;
return ListView.builder(
  itemCount: items.length,
  itemBuilder: (BuildContext context, int index) {
    return ListTile(
      title: Text(items[index].name),
      leading: CircleAvatar(
        backgroundImage:
            NetworkImage(items[index].owner.avatarUrl),
      ),
      subtitle: Text(items[index].description),
    );
  },
);

工作演示



完整的代码

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

// To parse this JSON data, do
//
//     final payload = payloadFromJson(jsonString);

import 'dart:convert';

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

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

class Payload {
  String totalCount;
  bool incompleteResults;
  List<Item> items;

  Payload({
    this.totalCount,
    this.incompleteResults,
    this.items,
  });

  factory Payload.fromJson(Map<String, dynamic> json) => Payload(
        totalCount: json["total_count"].toString(),
        incompleteResults: json["incomplete_results"],
        items: List<Item>.from(json["items"].map((x) => Item.fromJson(x))),
      );

  Map<String, dynamic> toJson() => {
        "total_count": totalCount,
        "incomplete_results": incompleteResults,
        "items": List<dynamic>.from(items.map((x) => x.toJson())),
      };
}

class Item {
  String id;
  String nodeId;
  String name;
  String fullName;
  bool private;
  Owner owner;
  String htmlUrl;
  String description;
  bool fork;
  String url;
  String forksUrl;
  String keysUrl;
  String collaboratorsUrl;
  String teamsUrl;
  String hooksUrl;
  String issueEventsUrl;
  String eventsUrl;
  String assigneesUrl;
  String branchesUrl;
  String tagsUrl;
  String blobsUrl;
  String gitTagsUrl;
  String gitRefsUrl;
  String treesUrl;
  String statusesUrl;
  String languagesUrl;
  String stargazersUrl;
  String contributorsUrl;
  String subscribersUrl;
  String subscriptionUrl;
  String commitsUrl;
  String gitCommitsUrl;
  String commentsUrl;
  String issueCommentUrl;
  String contentsUrl;
  String compareUrl;
  String mergesUrl;
  String archiveUrl;
  String downloadsUrl;
  String issuesUrl;
  String pullsUrl;
  String milestonesUrl;
  String notificationsUrl;
  String labelsUrl;
  String releasesUrl;
  String deploymentsUrl;
  DateTime createdAt;
  DateTime updatedAt;
  DateTime pushedAt;
  String gitUrl;
  String sshUrl;
  String cloneUrl;
  String svnUrl;
  String homepage;
  int size;
  int stargazersCount;
  int watchersCount;
  String language;
  bool hasIssues;
  bool hasProjects;
  bool hasDownloads;
  bool hasWiki;
  bool hasPages;
  int forksCount;
  dynamic mirrorUrl;
  bool archived;
  bool disabled;
  int openIssuesCount;
  License license;
  int forks;
  int openIssues;
  int watchers;
  DefaultBranch defaultBranch;
  double score;

  Item({
    this.id,
    this.nodeId,
    this.name,
    this.fullName,
    this.private,
    this.owner,
    this.htmlUrl,
    this.description,
    this.fork,
    this.url,
    this.forksUrl,
    this.keysUrl,
    this.collaboratorsUrl,
    this.teamsUrl,
    this.hooksUrl,
    this.issueEventsUrl,
    this.eventsUrl,
    this.assigneesUrl,
    this.branchesUrl,
    this.tagsUrl,
    this.blobsUrl,
    this.gitTagsUrl,
    this.gitRefsUrl,
    this.treesUrl,
    this.statusesUrl,
    this.languagesUrl,
    this.stargazersUrl,
    this.contributorsUrl,
    this.subscribersUrl,
    this.subscriptionUrl,
    this.commitsUrl,
    this.gitCommitsUrl,
    this.commentsUrl,
    this.issueCommentUrl,
    this.contentsUrl,
    this.compareUrl,
    this.mergesUrl,
    this.archiveUrl,
    this.downloadsUrl,
    this.issuesUrl,
    this.pullsUrl,
    this.milestonesUrl,
    this.notificationsUrl,
    this.labelsUrl,
    this.releasesUrl,
    this.deploymentsUrl,
    this.createdAt,
    this.updatedAt,
    this.pushedAt,
    this.gitUrl,
    this.sshUrl,
    this.cloneUrl,
    this.svnUrl,
    this.homepage,
    this.size,
    this.stargazersCount,
    this.watchersCount,
    this.language,
    this.hasIssues,
    this.hasProjects,
    this.hasDownloads,
    this.hasWiki,
    this.hasPages,
    this.forksCount,
    this.mirrorUrl,
    this.archived,
    this.disabled,
    this.openIssuesCount,
    this.license,
    this.forks,
    this.openIssues,
    this.watchers,
    this.defaultBranch,
    this.score,
  });

  factory Item.fromJson(Map<String, dynamic> json) => Item(
        id: json["id"].toString(),
        nodeId: json["node_id"],
        name: json["name"],
        fullName: json["full_name"],
        private: json["private"],
        owner: Owner.fromJson(json["owner"]),
        htmlUrl: json["html_url"],
        description: json["description"] == null ? null : json["description"],
        fork: json["fork"],
        url: json["url"],
        forksUrl: json["forks_url"],
        keysUrl: json["keys_url"],
        collaboratorsUrl: json["collaborators_url"],
        teamsUrl: json["teams_url"],
        hooksUrl: json["hooks_url"],
        issueEventsUrl: json["issue_events_url"],
        eventsUrl: json["events_url"],
        assigneesUrl: json["assignees_url"],
        branchesUrl: json["branches_url"],
        tagsUrl: json["tags_url"],
        blobsUrl: json["blobs_url"],
        gitTagsUrl: json["git_tags_url"],
        gitRefsUrl: json["git_refs_url"],
        treesUrl: json["trees_url"],
        statusesUrl: json["statuses_url"],
        languagesUrl: json["languages_url"],
        stargazersUrl: json["stargazers_url"],
        contributorsUrl: json["contributors_url"],
        subscribersUrl: json["subscribers_url"],
        subscriptionUrl: json["subscription_url"],
        commitsUrl: json["commits_url"],
        gitCommitsUrl: json["git_commits_url"],
        commentsUrl: json["comments_url"],
        issueCommentUrl: json["issue_comment_url"],
        contentsUrl: json["contents_url"],
        compareUrl: json["compare_url"],
        mergesUrl: json["merges_url"],
        archiveUrl: json["archive_url"],
        downloadsUrl: json["downloads_url"],
        issuesUrl: json["issues_url"],
        pullsUrl: json["pulls_url"],
        milestonesUrl: json["milestones_url"],
        notificationsUrl: json["notifications_url"],
        labelsUrl: json["labels_url"],
        releasesUrl: json["releases_url"],
        deploymentsUrl: json["deployments_url"],
        createdAt: DateTime.parse(json["created_at"]),
        updatedAt: DateTime.parse(json["updated_at"]),
        pushedAt: DateTime.parse(json["pushed_at"]),
        gitUrl: json["git_url"],
        sshUrl: json["ssh_url"],
        cloneUrl: json["clone_url"],
        svnUrl: json["svn_url"],
        homepage: json["homepage"] == null ? null : json["homepage"],
        size: json["size"],
        stargazersCount: json["stargazers_count"],
        watchersCount: json["watchers_count"],
        language: json["language"] == null ? null : json["language"],
        hasIssues: json["has_issues"],
        hasProjects: json["has_projects"],
        hasDownloads: json["has_downloads"],
        hasWiki: json["has_wiki"],
        hasPages: json["has_pages"],
        forksCount: json["forks_count"],
        mirrorUrl: json["mirror_url"],
        archived: json["archived"],
        disabled: json["disabled"],
        openIssuesCount: json["open_issues_count"],
        license:
            json["license"] == null ? null : License.fromJson(json["license"]),
        forks: json["forks"],
        openIssues: json["open_issues"],
        watchers: json["watchers"],
        defaultBranch: defaultBranchValues.map[json["default_branch"]],
        score: json["score"],
      );

  Map<String, dynamic> toJson() => {
        "id": id,
        "node_id": nodeId,
        "name": name,
        "full_name": fullName,
        "private": private,
        "owner": owner.toJson(),
        "html_url": htmlUrl,
        "description": description == null ? null : description,
        "fork": fork,
        "url": url,
        "forks_url": forksUrl,
        "keys_url": keysUrl,
        "collaborators_url": collaboratorsUrl,
        "teams_url": teamsUrl,
        "hooks_url": hooksUrl,
        "issue_events_url": issueEventsUrl,
        "events_url": eventsUrl,
        "assignees_url": assigneesUrl,
        "branches_url": branchesUrl,
        "tags_url": tagsUrl,
        "blobs_url": blobsUrl,
        "git_tags_url": gitTagsUrl,
        "git_refs_url": gitRefsUrl,
        "trees_url": treesUrl,
        "statuses_url": statusesUrl,
        "languages_url": languagesUrl,
        "stargazers_url": stargazersUrl,
        "contributors_url": contributorsUrl,
        "subscribers_url": subscribersUrl,
        "subscription_url": subscriptionUrl,
        "commits_url": commitsUrl,
        "git_commits_url": gitCommitsUrl,
        "comments_url": commentsUrl,
        "issue_comment_url": issueCommentUrl,
        "contents_url": contentsUrl,
        "compare_url": compareUrl,
        "merges_url": mergesUrl,
        "archive_url": archiveUrl,
        "downloads_url": downloadsUrl,
        "issues_url": issuesUrl,
        "pulls_url": pullsUrl,
        "milestones_url": milestonesUrl,
        "notifications_url": notificationsUrl,
        "labels_url": labelsUrl,
        "releases_url": releasesUrl,
        "deployments_url": deploymentsUrl,
        "created_at": createdAt.toIso8601String(),
        "updated_at": updatedAt.toIso8601String(),
        "pushed_at": pushedAt.toIso8601String(),
        "git_url": gitUrl,
        "ssh_url": sshUrl,
        "clone_url": cloneUrl,
        "svn_url": svnUrl,
        "homepage": homepage == null ? null : homepage,
        "size": size,
        "stargazers_count": stargazersCount,
        "watchers_count": watchersCount,
        "language": language == null ? null : language,
        "has_issues": hasIssues,
        "has_projects": hasProjects,
        "has_downloads": hasDownloads,
        "has_wiki": hasWiki,
        "has_pages": hasPages,
        "forks_count": forksCount,
        "mirror_url": mirrorUrl,
        "archived": archived,
        "disabled": disabled,
        "open_issues_count": openIssuesCount,
        "license": license == null ? null : license.toJson(),
        "forks": forks,
        "open_issues": openIssues,
        "watchers": watchers,
        "default_branch": defaultBranchValues.reverse[defaultBranch],
        "score": score,
      };
}

enum DefaultBranch { MASTER }

final defaultBranchValues = EnumValues({"master": DefaultBranch.MASTER});

class License {
  String key;
  String name;
  String spdxId;
  String url;
  String nodeId;

  License({
    this.key,
    this.name,
    this.spdxId,
    this.url,
    this.nodeId,
  });

  factory License.fromJson(Map<String, dynamic> json) => License(
        key: json["key"],
        name: json["name"],
        spdxId: json["spdx_id"],
        url: json["url"] == null ? null : json["url"],
        nodeId: json["node_id"],
      );

  Map<String, dynamic> toJson() => {
        "key": key,
        "name": name,
        "spdx_id": spdxId,
        "url": url == null ? null : url,
        "node_id": nodeId,
      };
}

class Owner {
  String login;
  String id;
  String nodeId;
  String avatarUrl;
  String gravatarId;
  String url;
  String htmlUrl;
  String followersUrl;
  String followingUrl;
  String gistsUrl;
  String starredUrl;
  String subscriptionsUrl;
  String organizationsUrl;
  String reposUrl;
  String eventsUrl;
  String receivedEventsUrl;
  Type type;
  bool siteAdmin;

  Owner({
    this.login,
    this.id,
    this.nodeId,
    this.avatarUrl,
    this.gravatarId,
    this.url,
    this.htmlUrl,
    this.followersUrl,
    this.followingUrl,
    this.gistsUrl,
    this.starredUrl,
    this.subscriptionsUrl,
    this.organizationsUrl,
    this.reposUrl,
    this.eventsUrl,
    this.receivedEventsUrl,
    this.type,
    this.siteAdmin,
  });

  factory Owner.fromJson(Map<String, dynamic> json) => Owner(
        login: json["login"],
        id: json["id"].toString(),
        nodeId: json["node_id"],
        avatarUrl: json["avatar_url"],
        gravatarId: json["gravatar_id"],
        url: json["url"],
        htmlUrl: json["html_url"],
        followersUrl: json["followers_url"],
        followingUrl: json["following_url"],
        gistsUrl: json["gists_url"],
        starredUrl: json["starred_url"],
        subscriptionsUrl: json["subscriptions_url"],
        organizationsUrl: json["organizations_url"],
        reposUrl: json["repos_url"],
        eventsUrl: json["events_url"],
        receivedEventsUrl: json["received_events_url"],
        type: typeValues.map[json["type"]],
        siteAdmin: json["site_admin"],
      );

  Map<String, dynamic> toJson() => {
        "login": login,
        "id": id,
        "node_id": nodeId,
        "avatar_url": avatarUrl,
        "gravatar_id": gravatarId,
        "url": url,
        "html_url": htmlUrl,
        "followers_url": followersUrl,
        "following_url": followingUrl,
        "gists_url": gistsUrl,
        "starred_url": starredUrl,
        "subscriptions_url": subscriptionsUrl,
        "organizations_url": organizationsUrl,
        "repos_url": reposUrl,
        "events_url": eventsUrl,
        "received_events_url": receivedEventsUrl,
        "type": typeValues.reverse[type],
        "site_admin": siteAdmin,
      };
}

enum Type { USER, ORGANIZATION }

final typeValues =
    EnumValues({"Organization": Type.ORGANIZATION, "User": Type.USER});

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,
      ),
      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> {
  static final String URL = "https://corona.lmao.ninja/countries";
  Future _future;

  Future<Payload> _fetchData() async {
    final response = await http.get(
        "https://api.github.com/search/repositories?q=created:%3E2018-10-22&sort=stars&order=desc");
    var list = payloadFromJson(response.body);
    return list;
  }

  @override
  void initState() {
    // TODO: implement initState
    super.initState();
    _future = _fetchData();
  }

  @override
  Widget build(BuildContext context) {
    return Scaffold(
        appBar: AppBar(
          title: Text(widget.title),
        ),
        body: FutureBuilder<Payload>(
            future: _future,
            builder: (BuildContext context, AsyncSnapshot<Payload> snapshot) {
              switch (snapshot.connectionState) {
                case ConnectionState.none:
                  return Text('Input a URL to start');
                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 {
                    var items = snapshot.data.items;
                    return ListView.builder(
                      itemCount: items.length,
                      itemBuilder: (BuildContext context, int index) {
                        return ListTile(
                          title: Text(items[index].name),
                          leading: CircleAvatar(
                            backgroundImage:
                                NetworkImage(items[index].owner.avatarUrl),
                          ),
                          subtitle: Text(items[index].description),
                        );
                      },
                    );
                  }
              }
            }));
  }
}