Question

我想要这个json的“标题”

我只想要项目中的标题。我可以通过诸如kind或etag之类的项获取每个数据，但是项为null。如何获得标题？

var data = await http.get("https://www.googleapis.com/youtube/v3/search?part=snippet&channelId={id}&maxResults=5&order=date&type=video&key={key}");
var jsonData =  json.decode(data.body);
String title = jsonData["items"][0]["title"];

{
    "kind": "youtube#searchListResponse",
    "etag": "\"Bdx4f4ps3xCOOo1WZ91nTLkRZ_c/g32qWHUfh9ZGLFfaJ4eAIWqe5As\"",
    "nextPageToken": "CAUQAA",
    "regionCode": "DE",
    "pageInfo": {
        "totalResults": 207,
        "resultsPerPage": 5
    },
    "items": [
        {
            "kind": "youtube#searchResult",
            "etag": "\"Bdx4f4ps3xCOOo1WZ91nTLkRZ_c/IPag1MLLCZWNOan8xL200XduRjk\"",
            "id": {
                "kind": "youtube#video",
                "videoId": "iWkAYZyrrWc"
            },
            "snippet": {
                "publishedAt": "2019-07-24T15:59:15.000Z",
                "channelId": "UC7TZhmZOk5nxVjBozb2EW4w",
                "title": "Afterbuy Statistiken - Performance Analyse und Controlling für Onlinehändler!",
                "description": "Die Afterbuy Statistik ist ein Auswertungstool zur Analyse der Performance eines Onlinehändlers im E-Commerce Markt. Wenn du den Mehrwert dieser Afterbuy ...",
                "thumbnails": {
                    "default": {
                        "url": "https://i.ytimg.com/vi/iWkAYZyrrWc/default.jpg",
                        "width": 120,
                        "height": 90
                    },
                    "medium": {
                        "url": "https://i.ytimg.com/vi/iWkAYZyrrWc/mqdefault.jpg",
                        "width": 320,
                        "height": 180
                  }
              }
          }
        }
      ]
   };
}

Answer 1

您错过了片段：

var title = jsonData()["items"][0].snippet["title"];
console.log(title);

function jsonData() {
   return {
  "kind": "youtube#searchListResponse",
  "etag": "\"Bdx4f4ps3xCOOo1WZ91nTLkRZ_c/g32qWHUfh9ZGLFfaJ4eAIWqe5As\"",
  "nextPageToken": "CAUQAA",
  "regionCode": "DE",
  "pageInfo": {
      "totalResults": 207,
      "resultsPerPage": 5
  },
  "items": [
      {
          "kind": "youtube#searchResult",
          "etag": "\"Bdx4f4ps3xCOOo1WZ91nTLkRZ_c/IPag1MLLCZWNOan8xL200XduRjk\"",
          "id": {
              "kind": "youtube#video",
              "videoId": "iWkAYZyrrWc"
          },
          "snippet": {
              "publishedAt": "2019-07-24T15:59:15.000Z",
              "channelId": "UC7TZhmZOk5nxVjBozb2EW4w",
              "title": "Afterbuy Statistiken - Performance Analyse und Controlling für Onlinehändler!",
              "description": "Die Afterbuy Statistik ist ein Auswertungstool zur Analyse der Performance eines Onlinehändlers im E-Commerce Markt. Wenn du den Mehrwert dieser Afterbuy ...",
              "thumbnails": {
                  "default": {
                      "url": "https://i.ytimg.com/vi/iWkAYZyrrWc/default.jpg",
                      "width": 120,
                      "height": 90
                  },
                  "medium": {
                      "url": "https://i.ytimg.com/vi/iWkAYZyrrWc/mqdefault.jpg",
                      "width": 320,
                      "height": 180
                  }
              }
          }
        }
      ]
   };
}

Answer 2

您可以使用this网站生成用于响应的Model类。

或者您也可以查看以下内容：JSON and serialization

并按如下所示使用它：

// If server returns an OK response, parse the JSON.
return YourModel.fromJson(json.decode(data.body));

Answer 3

如果您只想标题而又不想创建模型（您确实应该使用IMO）

伪代码

curl -v localhost:8080
    -H 'Content-Type: multipart/form-data'
    --form 'command={"test": "hello"};type=application/json'
    --form 'certificates=@example.jpg;type=image/jpeg'

Answer 4

您应按如下所示创建模型。

//要解析此JSON数据，请执行 // //最终结果= resultFromJson（jsonString）;

2nd Way:
import * as abc from './abc'

//Then use it like:
abc.function1();

下一步，

import 'dart:convert';

class Result {
    String kind;
    String etag;
    String nextPageToken;
    String regionCode;
    PageInfo pageInfo;
    List<Item> items;

    Result({
        this.kind,
        this.etag,
        this.nextPageToken,
        this.regionCode,
        this.pageInfo,
        this.items,
    });

    factory Result.fromRawJson(String str) => Result.fromJson(json.decode(str));

    String toRawJson() => json.encode(toJson());

    factory Result.fromJson(Map<String, dynamic> json) => new Result(
        kind: json["kind"] == null ? null : json["kind"],
        etag: json["etag"] == null ? null : json["etag"],
        nextPageToken: json["nextPageToken"] == null ? null : json["nextPageToken"],
        regionCode: json["regionCode"] == null ? null : json["regionCode"],
        pageInfo: json["pageInfo"] == null ? null : PageInfo.fromJson(json["pageInfo"]),
        items: json["items"] == null ? null : new List<Item>.from(json["items"].map((x) => Item.fromJson(x))),
    );

    Map<String, dynamic> toJson() => {
        "kind": kind == null ? null : kind,
        "etag": etag == null ? null : etag,
        "nextPageToken": nextPageToken == null ? null : nextPageToken,
        "regionCode": regionCode == null ? null : regionCode,
        "pageInfo": pageInfo == null ? null : pageInfo.toJson(),
        "items": items == null ? null : new List<dynamic>.from(items.map((x) => x.toJson())),
    };
}

class Item {
    String kind;
    String etag;
    Id id;
    Snippet snippet;

    Item({
        this.kind,
        this.etag,
        this.id,
        this.snippet,
    });

    factory Item.fromRawJson(String str) => Item.fromJson(json.decode(str));

    String toRawJson() => json.encode(toJson());

    factory Item.fromJson(Map<String, dynamic> json) => new Item(
        kind: json["kind"] == null ? null : json["kind"],
        etag: json["etag"] == null ? null : json["etag"],
        id: json["id"] == null ? null : Id.fromJson(json["id"]),
        snippet: json["snippet"] == null ? null : Snippet.fromJson(json["snippet"]),
    );

    Map<String, dynamic> toJson() => {
        "kind": kind == null ? null : kind,
        "etag": etag == null ? null : etag,
        "id": id == null ? null : id.toJson(),
        "snippet": snippet == null ? null : snippet.toJson(),
    };
}

class Id {
    String kind;
    String videoId;

    Id({
        this.kind,
        this.videoId,
    });

    factory Id.fromRawJson(String str) => Id.fromJson(json.decode(str));

    String toRawJson() => json.encode(toJson());

    factory Id.fromJson(Map<String, dynamic> json) => new Id(
        kind: json["kind"] == null ? null : json["kind"],
        videoId: json["videoId"] == null ? null : json["videoId"],
    );

    Map<String, dynamic> toJson() => {
        "kind": kind == null ? null : kind,
        "videoId": videoId == null ? null : videoId,
    };
}

class Snippet {
    DateTime publishedAt;
    String channelId;
    String title;
    String description;
    Thumbnails thumbnails;

    Snippet({
        this.publishedAt,
        this.channelId,
        this.title,
        this.description,
        this.thumbnails,
    });

    factory Snippet.fromRawJson(String str) => Snippet.fromJson(json.decode(str));

    String toRawJson() => json.encode(toJson());

    factory Snippet.fromJson(Map<String, dynamic> json) => new Snippet(
        publishedAt: json["publishedAt"] == null ? null : DateTime.parse(json["publishedAt"]),
        channelId: json["channelId"] == null ? null : json["channelId"],
        title: json["title"] == null ? null : json["title"],
        description: json["description"] == null ? null : json["description"],
        thumbnails: json["thumbnails"] == null ? null : Thumbnails.fromJson(json["thumbnails"]),
    );

    Map<String, dynamic> toJson() => {
        "publishedAt": publishedAt == null ? null : publishedAt.toIso8601String(),
        "channelId": channelId == null ? null : channelId,
        "title": title == null ? null : title,
        "description": description == null ? null : description,
        "thumbnails": thumbnails == null ? null : thumbnails.toJson(),
    };
}

class Thumbnails {
    Default thumbnailsDefault;
    Default medium;

    Thumbnails({
        this.thumbnailsDefault,
        this.medium,
    });

    factory Thumbnails.fromRawJson(String str) => Thumbnails.fromJson(json.decode(str));

    String toRawJson() => json.encode(toJson());

    factory Thumbnails.fromJson(Map<String, dynamic> json) => new Thumbnails(
        thumbnailsDefault: json["default"] == null ? null : Default.fromJson(json["default"]),
        medium: json["medium"] == null ? null : Default.fromJson(json["medium"]),
    );

    Map<String, dynamic> toJson() => {
        "default": thumbnailsDefault == null ? null : thumbnailsDefault.toJson(),
        "medium": medium == null ? null : medium.toJson(),
    };
}

class Default {
    String url;
    int width;
    int height;

    Default({
        this.url,
        this.width,
        this.height,
    });

    factory Default.fromRawJson(String str) => Default.fromJson(json.decode(str));

    String toRawJson() => json.encode(toJson());

    factory Default.fromJson(Map<String, dynamic> json) => new Default(
        url: json["url"] == null ? null : json["url"],
        width: json["width"] == null ? null : json["width"],
        height: json["height"] == null ? null : json["height"],
    );

    Map<String, dynamic> toJson() => {
        "url": url == null ? null : url,
        "width": width == null ? null : width,
        "height": height == null ? null : height,
    };
}

class PageInfo {
    int totalResults;
    int resultsPerPage;

    PageInfo({
        this.totalResults,
        this.resultsPerPage,
    });

    factory PageInfo.fromRawJson(String str) => PageInfo.fromJson(json.decode(str));

    String toRawJson() => json.encode(toJson());

    factory PageInfo.fromJson(Map<String, dynamic> json) => new PageInfo(
        totalResults: json["totalResults"] == null ? null : json["totalResults"],
        resultsPerPage: json["resultsPerPage"] == null ? null : json["resultsPerPage"],
    );

    Map<String, dynamic> toJson() => {
        "totalResults": totalResults == null ? null : totalResults,
        "resultsPerPage": resultsPerPage == null ? null : resultsPerPage,
    };
}

它应该在此时工作

Answer 5

您可以通过这种方式进行。

import 'dart:convert';

import 'json_objects.dart';

main(List<String> args) {
  var json = jsonDecode(_source) as Map<String, dynamic>;
  var response = Response1.fromJson(json);
  for (var item in response.items) {
    print(item.snippet.title);
  }
}

final _source = r'''
{
  "kind": "youtube#searchListResponse",
  "etag": "\"Bdx4f4ps3xCOOo1WZ91nTLkRZ_c/g32qWHUfh9ZGLFfaJ4eAIWqe5As\"",
  "nextPageToken": "CAUQAA",
  "regionCode": "DE",
  "pageInfo": {
    "totalResults": 207,
    "resultsPerPage": 5
  },
  "items": [
    {
      "kind": "youtube#searchResult",
      "etag": "\"Bdx4f4ps3xCOOo1WZ91nTLkRZ_c/IPag1MLLCZWNOan8xL200XduRjk\"",
      "id": {
        "kind": "youtube#video",
        "videoId": "iWkAYZyrrWc"
      },
      "snippet": {
        "publishedAt": "2019-07-24T15:59:15.000Z",
        "channelId": "UC7TZhmZOk5nxVjBozb2EW4w",
        "title": "Afterbuy Statistiken - Performance Analyse und Controlling für Onlinehändler!",
        "description": "Die Afterbuy Statistik ist ein Auswertungstool zur Analyse der Performance eines Onlinehändlers im E-Commerce Markt. Wenn du den Mehrwert dieser Afterbuy ...",
        "thumbnails": {
          "default": {
            "url": "https://i.ytimg.com/vi/iWkAYZyrrWc/default.jpg",
            "width": 120,
            "height": 90
          },
          "medium": {
            "url": "https://i.ytimg.com/vi/iWkAYZyrrWc/mqdefault.jpg",
            "width": 320,
            "height": 180
          }
        }
      }
    }
  ]
}''';

结果：

Afterbuy Statistiken - Performance Analyse und Controlling für Onlinehändler!

使用的数据模型（由工具自动生成）。

class Response1 {
  final String etag;
  final List<Response1Items> items;
  final String kind;
  final String nextPageToken;
  final Response1PageInfo pageInfo;
  final String regionCode;

  Response1(
      {this.etag,
      this.items,
      this.kind,
      this.nextPageToken,
      this.pageInfo,
      this.regionCode});

  factory Response1.fromJson(Map<String, dynamic> json) {
    return Response1(
      etag: json['etag'] as String,
      items: _toObjectList(json['items'], (e) => Response1Items.fromJson(e)),
      kind: json['kind'] as String,
      nextPageToken: json['nextPageToken'] as String,
      pageInfo:
          _toObject(json['pageInfo'], (e) => Response1PageInfo.fromJson(e)),
      regionCode: json['regionCode'] as String,
    );
  }

  Map<String, dynamic> toJson() {
    return {
      'etag': etag,
      'items': _fromList(items, (e) => e.toJson()),
      'kind': kind,
      'nextPageToken': nextPageToken,
      'pageInfo': pageInfo?.toJson(),
      'regionCode': regionCode,
    };
  }
}

class Response1Items {
  final String etag;
  final Response1ItemsId id;
  final String kind;
  final Response1ItemsSnippet snippet;

  Response1Items({this.etag, this.id, this.kind, this.snippet});

  factory Response1Items.fromJson(Map<String, dynamic> json) {
    return Response1Items(
      etag: json['etag'] as String,
      id: _toObject(json['id'], (e) => Response1ItemsId.fromJson(e)),
      kind: json['kind'] as String,
      snippet:
          _toObject(json['snippet'], (e) => Response1ItemsSnippet.fromJson(e)),
    );
  }

  Map<String, dynamic> toJson() {
    return {
      'etag': etag,
      'id': id?.toJson(),
      'kind': kind,
      'snippet': snippet?.toJson(),
    };
  }
}

class Response1ItemsId {
  final String kind;
  final String videoId;

  Response1ItemsId({this.kind, this.videoId});

  factory Response1ItemsId.fromJson(Map<String, dynamic> json) {
    return Response1ItemsId(
      kind: json['kind'] as String,
      videoId: json['videoId'] as String,
    );
  }

  Map<String, dynamic> toJson() {
    return {
      'kind': kind,
      'videoId': videoId,
    };
  }
}

class Response1ItemsSnippet {
  final String channelId;
  final String description;
  final DateTime publishedAt;
  final Response1ItemsSnippetThumbnails thumbnails;
  final String title;

  Response1ItemsSnippet(
      {this.channelId,
      this.description,
      this.publishedAt,
      this.thumbnails,
      this.title});

  factory Response1ItemsSnippet.fromJson(Map<String, dynamic> json) {
    return Response1ItemsSnippet(
      channelId: json['channelId'] as String,
      description: json['description'] as String,
      publishedAt: _toDateTime(json['publishedAt']),
      thumbnails: _toObject(json['thumbnails'],
          (e) => Response1ItemsSnippetThumbnails.fromJson(e)),
      title: json['title'] as String,
    );
  }

  Map<String, dynamic> toJson() {
    return {
      'channelId': channelId,
      'description': description,
      'publishedAt': _fromDateTime(publishedAt),
      'thumbnails': thumbnails?.toJson(),
      'title': title,
    };
  }
}

class Response1ItemsSnippetThumbnail {
  final int height;
  final String url;
  final int width;

  Response1ItemsSnippetThumbnail({this.height, this.url, this.width});

  factory Response1ItemsSnippetThumbnail.fromJson(Map<String, dynamic> json) {
    return Response1ItemsSnippetThumbnail(
      height: json['height'] as int,
      url: json['url'] as String,
      width: json['width'] as int,
    );
  }

  Map<String, dynamic> toJson() {
    return {
      'height': height,
      'url': url,
      'width': width,
    };
  }
}

class Response1ItemsSnippetThumbnails {
  final Response1ItemsSnippetThumbnail default_;
  final Response1ItemsSnippetThumbnail medium;

  Response1ItemsSnippetThumbnails({this.default_, this.medium});

  factory Response1ItemsSnippetThumbnails.fromJson(Map<String, dynamic> json) {
    return Response1ItemsSnippetThumbnails(
      default_: _toObject(
          json['default'], (e) => Response1ItemsSnippetThumbnail.fromJson(e)),
      medium: _toObject(
          json['medium'], (e) => Response1ItemsSnippetThumbnail.fromJson(e)),
    );
  }

  Map<String, dynamic> toJson() {
    return {
      'default': default_?.toJson(),
      'medium': medium?.toJson(),
    };
  }
}

class Response1PageInfo {
  final int resultsPerPage;
  final int totalResults;

  Response1PageInfo({this.resultsPerPage, this.totalResults});

  factory Response1PageInfo.fromJson(Map<String, dynamic> json) {
    return Response1PageInfo(
      resultsPerPage: json['resultsPerPage'] as int,
      totalResults: json['totalResults'] as int,
    );
  }

  Map<String, dynamic> toJson() {
    return {
      'resultsPerPage': resultsPerPage,
      'totalResults': totalResults,
    };
  }
}

String _fromDateTime(data) {
  if (data == null) {
    return null;
  }
  if (data is DateTime) {
    return data.toIso8601String();
  }
  return data as String;
}

List _fromList(data, Function(dynamic) toJson) {
  if (data == null) {
    return null;
  }
  var result = [];
  for (var element in data) {
    var value;
    if (element != null) {
      value = toJson(element);
    }
    result.add(value);
  }
  return result;
}

DateTime _toDateTime(data) {
  if (data == null) {
    return null;
  }
  if (data is String) {
    return DateTime.parse(data);
  }
  return data as DateTime;
}

T _toObject<T>(data, T Function(Map<String, dynamic>) fromJson) {
  if (data == null) {
    return null;
  }
  return fromJson(data as Map<String, dynamic>);
}

List<T> _toObjectList<T>(data, T Function(Map<String, dynamic>) fromJson) {
  if (data == null) {
    return null;
  }
  var result = <T>[];
  for (var element in data) {
    T value;
    if (element != null) {
      value = fromJson(element as Map<String, dynamic>);
    }
    result.add(value);
  }
  return result;
}

/*
Response1:
  "kind": String
  "etag": String
  "nextPageToken": String
  "regionCode": String
  "pageInfo": Response1PageInfo
  "items": List<Response1Items>

Response1PageInfo:
  "totalResults": int
  "resultsPerPage": int

Response1Items:
  "kind": String
  "etag": String
  "id": Response1ItemsId
  "snippet": Response1ItemsSnippet

Response1ItemsId:
  "kind": String
  "videoId": String

Response1ItemsSnippet:
  "publishedAt": DateTime
  "channelId": String
  "title": String
  "description": String
  "thumbnails": Response1ItemsSnippetThumbnails

Response1ItemsSnippetThumbnails:
  "default": Response1ItemsSnippetThumbnail
  "medium": Response1ItemsSnippetThumbnail

Response1ItemsSnippetThumbnail:
  "url": String
  "width": int
  "height": int
*/

Flutter从复杂的JSON获取数据

5 个答案: