输入“列表<动态>”不是'List< int>'类型的子类型哪里 [英] type 'List<dynamic>' is not a subtype of type 'List<int>' where

问题描述

我是Flutter的新手，我尝试运行一个github项目，但是遇到类似类型List dynamic的错误，而不是类型List int的子类型。 Github链接

I am new to Flutter, I try to run one github project but got 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，谢谢您。

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>();

类型没有具体的泛型类型。
genreIds 需要 List< int> 而不是 List （或 List< dynamic> ），因此在分配值之前，您需要将该值带入所需的类型。

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错误，则可能是因为您已升级到Dart版本，其中-preview-dart-2 成为默认值（以前是选择加入的）

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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