json - 如何继续在 flutter 中接收 JSON 数组并解析它？

Question

我正在尝试从 Web 服务 URL 获取 JSON 数组并在 JSON 中解析它。问题是我正在关注的教程显示接收一个 JSOn obj 并解析它，但我需要知道如何接收 JSON 数组并解析它。下面是我正在处理的代码，我卡住了。

型号

class Fact {
  int id;
  int fact_id;
  String fact;
  String image;
  String reference;

  Fact(this.id, this.fact_id, this.fact, this.image, this.reference);

  Fact.fromJson(Map<String, dynamic> json)
    : id = json['id'],
      fact_id = json['fact_id'],
      fact = json['fact'],
      image = json['image'],
      reference = json['reference'];

    Map<String, dynamic> toJson() =>
    {
      'id' : id,
      'fact_id': fact_id,
      'fact': fact,
      'image': image,
      'reference': reference,
    };
}

我不知道如何为我从网络服务获得的事实数组编写此代码。

事实下载管理器

class FactsManager {
  var constants = Constants();

  fetchFacts() {
    final lastFactId = 0;
    var fetchRequestUrl = constants.fetch_facts_url;

    if (lastFactId == 0) {
      fetchRequestUrl = fetchRequestUrl + "?count=" + constants.firstTimePostCount.toString();
    } else {
      fetchRequestUrl = fetchRequestUrl + "?count=" + constants.firstTimePostCount.toString() + "&last_id=" + lastFactId.toString();
    }
    Future<List<Fact>> fetchPost() async {
      final response = await http.get(fetchRequestUrl);

      if (response.statusCode == 200) {
        return List<Fact>
      }
    }
  }
}

我正在尝试解析的示例数据。

[
    {
        "id": "407",
        "fact": "Monsanto once tried to genetically engineer blue cotton, to produce denim without the use of dyes, reducing the pollution involved in the dyeing process.   ",
        "reference": null,
        "image": "http:\/\/quickfacts.me\/wp-content\/uploads\/2015\/06\/fact492.png",
        "fact_id": "1"
    },
    {
        "id": "560",
        "fact": "You can count from zero to nine hundred ninety-nine without ever having to use the letter \"a\"   ",
        "reference": null,
        "image": "http:\/\/quickfacts.me\/wp-content\/uploads\/2015\/06\/fact04.png",
        "fact_id": "2"
    },
    {
        "id": "564",
        "fact": "In order to keep the project a secret, the British army used the innocuous name \"mobile water carriers\" for a motorized weapons project - which is the reason we call them \"tanks\".   ",
        "reference": null,
        "image": "http:\/\/quickfacts.me\/wp-content\/uploads\/2015\/06\/fact116.png",
        "fact_id": "3"
    },
    {
        "id": "562",
        "fact": "In 2010 the mummified corpse of Sogen Kato, thought to be Tokyo's oldest man, was found in his bedroom by government officials. He had actually died in 1978.   ",
        "reference": null,
        "image": "http:\/\/quickfacts.me\/wp-content\/uploads\/2015\/06\/fact216.png",
        "fact_id": "4"
    },
    {
        "id": "566",
        "fact": "In 1927 the US Supreme Court ruled it constitutional for the government to forcefully sterilize mentally handicapped people   ",
        "reference": null,
        "image": "http:\/\/quickfacts.me\/wp-content\/uploads\/2015\/06\/fact316.png",
        "fact_id": "5"
    }
]

Answer 1

您可以执行以下操作:

String receivedJson = "... Your JSON string ....";
List<dynamic> list = json.decode(receivedJson);
Fact fact = Fact.fromJson(list[0]);

无论如何，您必须在您的 json 字符串和您制作的 Fact 类中考虑以下内容:

• 在 json 字符串中，id 和 fact_id 是字符串，您将它们视为 int。您要么更改 json 要么更改 Fact 类
• json 字符串中的一些字符串会产生错误，因为它们有额外的引号，这会混淆解码器。

作品的json字符串如下:

String receivedJson = """
[
    {
        "id": 407,
        "fact": "Monsanto once tried to genetically engineer blue cotton, to produce denim without the use of dyes, reducing the pollution involved in the dyeing process.   ",
        "reference": null,
        "image": "http:\/\/quickfacts.me\/wp-content\/uploads\/2015\/06\/fact492.png",
        "fact_id": 1
    }
]
    """;