输入'列表<动态>'不是“List<int>"类型的子类型在哪里 [英] type &#39;List&lt;dynamic&gt;&#39; is not a subtype of type &#39;List&lt;int&gt;&#39; where

问题描述

我是 Flutter 的新手，我尝试运行一个 GitHub 项目，但遇到了一个错误，比如 List dynamic 不是 List int 类型的子类型.Github 链接

I am new to Flutter, I try to run one GitHub project but got an error like type List dynamic is not a subtype of type List int where. Github Link

错误行

List<int> genreIds;

MediaItem._internalFromJson(Map jsonMap, {MediaType type: MediaType.movie})
      :
        type = type,
        id = jsonMap["id"].toInt(),
        voteAverage = jsonMap["vote_average"].toDouble(),
        title = jsonMap[(type == MediaType.movie ? "title" : "name")],
        posterPath = jsonMap["poster_path"] ?? "",
        backdropPath = jsonMap["backdrop_path"] ?? "",
        overview = jsonMap["overview"],
        releaseDate = jsonMap[(type == MediaType.movie
            ? "release_date"
            : "first_air_date")],

        genreIds = jsonMap["genre_ids"];//in this line


}

以上代码文件

任何帮助将不胜感激，在此先感谢您.

Any help will be appreciated, thank you in advance.

推荐答案

更改

genreIds = jsonMap["genre_ids"];

到

genreIds = jsonMap["genre_ids"].cast<int>();

JSON 映射或列表中的类型没有具体的泛型类型.genreIds 需要 List 而不是 List(或 List)，因此您需要将值设为所需的类型，然后才能对其进行赋值.

types in JSON maps or lists don't have concrete generic types. genreIds requires a List<int> not a List (or List<dynamic>), therefore you need to bring the value to its required type before you can assign it.

如果您之前没有看到相同代码的此错误，那么可能是因为您升级到了 Dart 版本，其中 --preview-dart-2 成为默认值(它是 opt-在以前)

If you haven't seen this error earlier for the same code, then it's probably because you upgraded to a Dart version where --preview-dart-2 became the default (it was opt-in previously)

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