需要帮助在 Flutter 中解析 JSON

Question

我正在尝试从 Flutter 中的互联网获取数据。但是我在 JSON 解析时遇到错误。谁能告诉我是什么问题？

我正在尝试从此 URL 获取数据

https://swapi.co/api/starships/

示例 JSON

{
    “计数”：37， 
    "next": "https://swapi.co/api/starships/?page=2", 
    “上一个”：空， 
    “结果”： [
        {
            "name": "执行者", 
            "model": "执行级星无畏", 
            "manufacturer": "Kuat Drive Yards, Fondor Shipyards", 
            "cost_in_credits": "1143350000", 
            "长度": "19000", 
            "max_atmophering_speed": "不适用", 
            “船员”：“279144”， 
            "乘客": "38000", 
            "cargo_capacity": "250000000", 
            "消耗品": "6 年", 
            "hyperdrive_rating": "2.0", 
            "MGLT": "40", 
            "starship_class": "星无畏", 
            “飞行员”：[]， 
            “电影”：[
                "https://swapi.co/api/films/2/", 
                “https://swapi.co/api/films/3/”
            ], 
            “创建”：“2014-12-15T12：31：42.547000Z”， 
            “编辑”：“2017-04-19T10：56：06.685592Z”， 
            "url": "https://swapi.co/api/starships/15/"
        }, 

    ]
}

模型类

class RestModel {
    final String name;
    final String model;
    final String manufacturer;
    final String cost_in_credits;
    final String length;
    final String max_atmosphering_speed;
    final String crew;
    final String passengers;
    final String cargo_capacity;
    final String consumables;
    final String hyperdrive_rating;
    final String MGLT;
    final String starship_class;
    final List films;
    final String pilots;
    final String created;
    final String edited;
    final String url;

    RestModel(
        {this.name,
        this.model,
        this.manufacturer,
        this.cost_in_credits,
        this.length,
        this.max_atmosphering_speed,
        this.crew,
        this.passengers,
        this.cargo_capacity,
        this.consumables,
        this.hyperdrive_rating,
        this.MGLT,
        this.starship_class,
        this.films,
        this.pilots,
        this.created,
        this.edited,
        this.url});

    factory RestModel.fromJson(Map<String, dynamic> json) {
        return RestModel(
            name: json["name"],
            model: json["model"],
            manufacturer: json["manufacturer"],
            cost_in_credits: json["cost_in_credits"],
            max_atmosphering_speed: json["max_atmosphering_speed"],
            crew: json["crew"],
            passengers: json["passengers"],
            cargo_capacity: json["cargo_capacity"],
            consumables: json["consumables"],
            hyperdrive_rating: json["hyperdrive_rating"],
            MGLT: json["MGLT"],
            starship_class: json["starship_class"],
            films: json["flims"],
            pilots: json["pilots"],
            created: json["created"],
            edited: json["edited"],
            url: json["url"],
        );
    }
}

颤振代码是：

final link = "https://swapi.co/api/starships/";

List<RestModel> list;

Future getData() async {
    var res = await http
    .get(Uri.encodeFull(link), headers: {"Accept":"application/json"});

    if (res.statusCode == 200) {
        var data = json.decode(res.body);
        var rest = data["results"];
        for (var model in rest) {
            list.add(RestModel.fromJson(model));
        }
        print("List Size: ${list.length}");
    }  
}

主要问题是当它尝试从 JSON 填充数据时。

RestModel.fromJson(model)

所以我必须改变才能解决这个问题。

Answer 1

尝试将数据 ' results' 转换为List，如下所示：

var rest = data["results"] as List; 

更新

现在我们知道错误日志：“在‘RestModel’类中没有声明静态方法‘fromJson’”

这是因为您在这一行中使用了静态方法：

list.add(RestModel.fromJson(model));

您必须更改调用才能使用工厂构造函数，如下所示：

list.add(new RestModel.fromJson(model));