如何修复此错误类型“_InternalLinkedHashMap<String, dynamic>”不是“FutureOr<List<dynamic>>”类型的子类

Posted 2023-02-23

【中文标题】如何修复此错误类型“_InternalLinkedHashMap<String, dynamic>”不是“FutureOr<List<dynamic>>”类型的子类型

【英文标题】：how to fix this error type '_InternalLinkedHashMap<String, dynamic>' is not a subtype of type 'FutureOr<List<dynamic>>'

【发布时间】：2021-01-18 17:26:17

【问题描述】：

您好，我是颤振飞镖的初学者。在这里，我试图从我的 API 显示列表视图，但出现错误。 错误

发生了异常。 _TypeError（类型 '_InternalLinkedHashMap' 不是类型 'FutureOr' 的子类型）

我认为我的代码到目前为止还不错，但是 Future list 异步行代码有问题。

错误截图：Screenshot

代码：

class ShipsApps 
int id;
String port_name;
int id_typort;
String description;

ShipsApps(this.id, this.port_name, this.id_typort, this.description);

factory ShipsApps.fromJson(Map<String, dynamic> json) 
return ShipsApps(
    id: json['id'],
    port_name: json['port_name'],
    id_typort: json['id_typort'],
    description: json['description']);



class _hotelDetailState extends State<hotelDetail> 
Future<List<dynamic>> getData() async 
// final String apiURL = ;
var response =
    await http.get('https://api.batulima.com/v1_ships/port_list');
return json.decode(response.body);


Widget build(BuildContext context) 
double _height = MediaQuery.of(context).size.height;
double _width = MediaQuery.of(context).size.width;

var _relatedPostVar = Column(
  mainAxisAlignment: MainAxisAlignment.start,
  crossAxisAlignment: CrossAxisAlignment.start,
  children: <Widget>[
    Padding(
      padding: const EdgeInsets.only(left: 20.0, right: 20.0, top: 40.0),
      child: Row(
          mainAxisAlignment: MainAxisAlignment.spaceBetween,
          children: <Widget>[
            Text(
              "Related Post",
              style: TextStyle(
                  fontFamily: "Sofia",
                  fontSize: 20.0,
                  fontWeight: FontWeight.w700),
            ),
            Text(
              "See all",
              style: TextStyle(
                  fontFamily: "Sofia",
                  fontSize: 16.0,
                  fontWeight: FontWeight.w300),
            ),
          ]),
    ),
    SizedBox(
      height: 10.0,
    ),
    Container(
      child: FutureBuilder<List>(
        future: getData(),
        builder: (context, snapshot) 
          if (snapshot.hasError) print(snapshot.error);
          return snapshot.hasData
              ? new ItemList(
                  list: snapshot.data,
                )
              : new Center();
        ,
      ),
    ),
    SizedBox(
      height: 40.0,
    ),
  ],
);



Widget _relatedPost(String image, title, location, ratting) 
return Padding(
padding: const EdgeInsets.all(8.0),
child: Column(
  mainAxisAlignment: MainAxisAlignment.start,
  crossAxisAlignment: CrossAxisAlignment.start,
  children: <Widget>[
    Container(
      height: 110.0,
      width: 180.0,
      decoration: BoxDecoration(
          image:
              DecorationImage(image: AssetImage(image), fit: BoxFit.cover),
          color: Colors.black12,
          borderRadius: BorderRadius.all(Radius.circular(10.0)),
          boxShadow: [
            BoxShadow(
                blurRadius: 5.0,
                color: Colors.black12.withOpacity(0.1),
                spreadRadius: 2.0)
          ]),
    ),
    SizedBox(
      height: 5.0,
    ),
    Text(
      title,
      style: TextStyle(
          fontFamily: "Sofia",
          fontWeight: FontWeight.w600,
          fontSize: 17.0,
          color: Colors.black87),
    ),
    SizedBox(
      height: 2.0,
    ),
    Row(
      mainAxisAlignment: MainAxisAlignment.start,
      crossAxisAlignment: CrossAxisAlignment.start,
      children: <Widget>[
        Icon(
          Icons.location_on,
          size: 18.0,
          color: Colors.black12,
        ),
        Text(
          location,
          style: TextStyle(
              fontFamily: "Sofia",
              fontWeight: FontWeight.w500,
              fontSize: 15.0,
              color: Colors.black26),
        ),
      ],
    ),
    Row(
      mainAxisAlignment: MainAxisAlignment.spaceBetween,
      crossAxisAlignment: CrossAxisAlignment.center,
      children: <Widget>[
        Icon(
          Icons.star,
          size: 18.0,
          color: Colors.yellow,
        ),

        Padding(
          padding: const EdgeInsets.only(top: 3.0),
          child: Text(
            ratting,
            style: TextStyle(
                fontWeight: FontWeight.w700,
                fontFamily: "Sofia",
                fontSize: 13.0),
          ),
        ),

        // Text("(233 Rating)",style: TextStyle(fontWeight: FontWeight.w500,fontFamily:  "Sofia",fontSize: 11.0,color: Colors.black45),),
        SizedBox(
          width: 35.0,
        ),
      ],
    ),
  ],
),
);

class ItemList extends StatelessWidget 
final List list;
ItemList(this.list);

@override
Widget build(BuildContext context) 
return ListView.builder(
  scrollDirection: Axis.horizontal,
  shrinkWrap: true,
  itemCount: list.length,
  itemBuilder: (context, i) 
    return _relatedPost(
        "list[i]['port_name'].toString()", "list[i]['id'].toString()", "list[i]['id_typort'].toString()", "list[i]['description'].toString()");
  ,
);

【问题讨论】：

如果问题没有解决，请告诉我。

【参考方案1】：

您的 api 返回一个 InternalLinkedHashMap，它是 Map 对象的子类型。 但是您的 FutureBuilder 假定您的 getData() 返回一个列表。 您的 api 返回类似于以下对象的内容：

  success: "true",
  data: [//data],

所以改用这个：

class ShipsApps 
int id;
String port_name;
int id_typort;
String description;

ShipsApps(this.id, this.port_name, this.id_typort, this.description);

factory ShipsApps.fromJson(Map<String, dynamic> json) 
return ShipsApps(
    id: json['id'],
    port_name: json['port_name'],
    id_typort: json['id_typort'],
    description: json['description']);



class _hotelDetailState extends State<hotelDetail> 
Future<Map> getData() async 
// final String apiURL = ;
var response =
    await http.get('https://api.batulima.com/v1_ships/port_list');
return json.decode(response.body) as Map<String, dynamic>;


Widget build(BuildContext context) 
double _height = MediaQuery.of(context).size.height;
double _width = MediaQuery.of(context).size.width;

var _relatedPostVar = Column(
  mainAxisAlignment: MainAxisAlignment.start,
  crossAxisAlignment: CrossAxisAlignment.start,
  children: <Widget>[
    Padding(
      padding: const EdgeInsets.only(left: 20.0, right: 20.0, top: 40.0),
      child: Row(
          mainAxisAlignment: MainAxisAlignment.spaceBetween,
          children: <Widget>[
            Text(
              "Related Post",
              style: TextStyle(
                  fontFamily: "Sofia",
                  fontSize: 20.0,
                  fontWeight: FontWeight.w700),
            ),
            Text(
              "See all",
              style: TextStyle(
                  fontFamily: "Sofia",
                  fontSize: 16.0,
                  fontWeight: FontWeight.w300),
            ),
          ]),
    ),
    SizedBox(
      height: 10.0,
    ),
    Container(
      child: FutureBuilder<Map>(
        future: getData(),
        builder: (context, snapshot) 
          if (snapshot.hasError) print(snapshot.error);
          return snapshot.hasData
              ? new ItemList(
                  list: snapshot.data["data"],
                )
              : new Center();
        ,
      ),
    ),
    SizedBox(
      height: 40.0,
    ),
  ],
);



Widget _relatedPost(String image, title, location, ratting) 
return Padding(
padding: const EdgeInsets.all(8.0),
child: Column(
  mainAxisAlignment: MainAxisAlignment.start,
  crossAxisAlignment: CrossAxisAlignment.start,
  children: <Widget>[
    Container(
      height: 110.0,
      width: 180.0,
      decoration: BoxDecoration(
          image:
              DecorationImage(image: AssetImage(image), fit: BoxFit.cover),
          color: Colors.black12,
          borderRadius: BorderRadius.all(Radius.circular(10.0)),
          boxShadow: [
            BoxShadow(
                blurRadius: 5.0,
                color: Colors.black12.withOpacity(0.1),
                spreadRadius: 2.0)
          ]),
    ),
    SizedBox(
      height: 5.0,
    ),
    Text(
      title,
      style: TextStyle(
          fontFamily: "Sofia",
          fontWeight: FontWeight.w600,
          fontSize: 17.0,
          color: Colors.black87),
    ),
    SizedBox(
      height: 2.0,
    ),
    Row(
      mainAxisAlignment: MainAxisAlignment.start,
      crossAxisAlignment: CrossAxisAlignment.start,
      children: <Widget>[
        Icon(
          Icons.location_on,
          size: 18.0,
          color: Colors.black12,
        ),
        Text(
          location,
          style: TextStyle(
              fontFamily: "Sofia",
              fontWeight: FontWeight.w500,
              fontSize: 15.0,
              color: Colors.black26),
        ),
      ],
    ),
    Row(
      mainAxisAlignment: MainAxisAlignment.spaceBetween,
      crossAxisAlignment: CrossAxisAlignment.center,
      children: <Widget>[
        Icon(
          Icons.star,
          size: 18.0,
          color: Colors.yellow,
        ),

        Padding(
          padding: const EdgeInsets.only(top: 3.0),
          child: Text(
            ratting,
            style: TextStyle(
                fontWeight: FontWeight.w700,
                fontFamily: "Sofia",
                fontSize: 13.0),
          ),
        ),

        // Text("(233 Rating)",style: TextStyle(fontWeight: FontWeight.w500,fontFamily:  "Sofia",fontSize: 11.0,color: Colors.black45),),
        SizedBox(
          width: 35.0,
        ),
      ],
    ),
  ],
),
);

class ItemList extends StatelessWidget 
final List list;
ItemList(this.list);

@override
Widget build(BuildContext context) 
return ListView.builder(
  scrollDirection: Axis.horizontal,
  shrinkWrap: true,
  itemCount: list.length,
  itemBuilder: (context, i) 
    return _relatedPost(
        "list[i]['port_name'].toString()", "list[i]['id'].toString()", "list[i]['id_typort'].toString()", "list[i]['description'].toString()");
  ,
);

【讨论】：

非常感谢先生，它有效。你救了我的命:')

@Aphron 不客气 ;)

先生，您能再帮我一次吗？我需要你的帮助，但我不知道如何联系你。我有同样的错误。

这是我的电子邮件：[e-mail]