Flutter - type '_InternalLinkedHashMap<String, dynamic> 不是 List<dynamic> 类型的子类型
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【中文标题】Flutter - type \'_InternalLinkedHashMap<String, dynamic> 不是 List<dynamic> 类型的子类型【英文标题】：Flutter - type '_InternalLinkedHashMap<String, dynamic> is not a subtype of type List<dynamic>Flutter - type '_InternalLinkedHashMap<String, dynamic> 不是 List<dynamic> 类型的子类型 【发布时间】：2021-01-22 02:14:10 【问题描述】：你好我创建了一个新的flutter应用程序，我的数据库是mysql数据库，我的Json数据是一个数组，我已经尽力做到最好但总是弹出这个错误：
type '_InternalLinkedHashMap<String, dynamic> is not a subtype of type List<dynamic>
Dataclass.dart
class FolderList
final List<Data> data;
FolderList(this.data);
factory FolderList.fromJson(Map<String, dynamic> json)
return FolderList(
data: json['folders'] != null ? (json['folders'] as List).map((i) => Data.fromJson(i)).toList() : null,
);
Map<String, dynamic> toJson()
final Map<String, dynamic> data = new Map<String, dynamic>();
if (this.data != null)
data['folders'] = this.data.map((v) => v.toJson()).toList();
return data;
class Data
final String id;
final String name;
Data(this.id, this.name);
factory Data.fromJson(Map<String, dynamic> json)
return Data(
id: json['id'],
name: json['name'],
);
Map<String, dynamic> toJson()
final Map<String, dynamic> data = new Map<String, dynamic>();
data['id'] = this.id;
data['name'] = this.name;
return data;
但是当我尝试解码 json 并通过 future 函数和这里是代码的小部件解析它时
class SecondScreen extends StatefulWidget
final YearsMain value;
SecondScreen(Key key, this.value) : super(key: key);
@override
_SecondScreenState createState() => _SecondScreenState();
class _SecondScreenState extends State<SecondScreen>
Future<List<FolderList>>fellowSubject() async
final jsonEndpoint =
"http://msc-mu.com/api_verfication.php";
final response = await http.post(jsonEndpoint,body:
'flag':'selectfellowsubjects',
'parentsubject':widget.value.id
);
if (response.statusCode == 200)
List<dynamic> data = json.decode(response.body);
return data;
else
throw Exception('We were not able to successfully download the Main Subjects.');
@override
void initState()
// TODO: implement initState
super.initState();
print(widget.value.id);
@override
Widget build(BuildContext context)
return Scaffold(
body: Center(
child: new FutureBuilder<List<FolderList>>(
future: fellowSubject(),
builder: (context, snapshot)
if (snapshot.hasData)
List<FolderList> fellow = snapshot.data;
return ListViewFellow(fellow);
else if (snapshot.hasError)
return Text('$snapshot.error');
return CircularProgressIndicator();
,
),
),
);
ListViewFellow
class ListViewFellow extends StatelessWidget
final List<FolderList> fellowSubject;
ListViewFellow(this.fellowSubject);
@override
Widget build(BuildContext context)
return StaggeredGridView.countBuilder(
crossAxisCount: 4,
itemBuilder: (BuildContext context, int currentIndex)
return createFellowItems(fellowSubject[currentIndex], context);
,
staggeredTileBuilder: (int currentIndex) =>
new StaggeredTile.count(2, currentIndex.isEven ? 2 : 2),
mainAxisSpacing: 4.0,
crossAxisSpacing: 1.0,
);
Widget createFellowItems(FolderList fellowData ,BuildContext context )
return GestureDetector(
child: Container(
margin: EdgeInsets.all(15.0),
decoration: BoxDecoration(
color: Color(0xff131535),
borderRadius: BorderRadius.circular(10.0),
),
child: Center(
child:
(Text(fellowData.data[0].name))
),
),
onTap: ()
var route = new MaterialPageRoute(
builder: (BuildContext context) => new DownloadPage(
value: fellowData,
),
);
Navigator.of(context).push(route);
);
我总是遇到上述错误我已经尝试了所有方法但对我没有任何效果，任何人都可以提供更好的解决方案吗？
Json 结构*
"folders":[
"id":2107,
"name":"Labs ",
"img":null,
"haschild":1,
"parentid":1955,
"createdate":"2019-09-30 03:00:39",
"inarchive":0,
"active":1
,
"id":2108,
"name":"L1",
"img":null,
"haschild":0,
"parentid":1955,
"createdate":"2019-09-30 03:00:45",
"inarchive":0,
"active":1
,
"id":2130,
"name":"L2",
"img":null,
"haschild":0,
"parentid":1955,
"createdate":"2019-10-02
02:39:11",
"inarchive":0,
"active":1
,
"id":2175,
"name":"L3",
"img":null,
"haschild":1,
"parentid":1955,
"createdate":"2019-10-07 03:43:15",
"inarchive":0,
"active":1
,
"id":2202,
"name":"L4",
"img":null,
"haschild":0,
"parentid":1955,
"createdate":"2019-10-09 02:08:10",
"inarchive":0,
"active":1
,
"id":2227,
"name":"\u0645\u0631\u0627\u062c\u0639\u0627\u062a
",
"img":null,
"haschild":1,
"parentid":1955,
"createdate":"2019-10-11 05:15:43",
"inarchive":0,
"active":1
,
"id":2242,
"name":"L5",
"img":null,
"haschild":0,
"parentid":1955,
"createdate":"2019-10-14 03:45:24",
"inarchive":0,
"active":1
,
"id":2257,
"name":"L6",
"img":null,
"haschild":0,
"parentid":1955,
"createdate":"2019-10-16
06:23:41",
"inarchive":0,
"active":1
,
"id":2269,
"name":"L7",
"img":null,
"haschild":0,
"parentid":1955,
"createdate":"2019-10-21 03:39:12",
"inarchive":0,
"active":1
,
"id":2309,
"name":"L8",
"img":null,
"haschild":0,
"parentid":1955,
"createdate":"2019-10-23 05:14:48",
"inarchive":0,
"active":1
,
"id":2310,
"name":"L8",
"img":null,
"haschild":0,
"parentid":1955,
"createdate":"2019-10-23
05:14:51",
"inarchive":0,
"active":1
,
"id":2346,
"name":"L9",
"img":null,
"haschild":0,
"parentid":1955,
"createdate":"2019-10-28 04:22:24",
"inarchive":0,
"active":1
,
"id":2370,
"name":"L10",
"img":null,
"haschild":0,
"parentid":1955,
"createdate":"2019-10-30 03:02:00",
"inarchive":0,
"active":1
,
"id":2446,
"name":"L11",
"img":null,
"haschild":0,
"parentid":1955,
"createdate":"2019-11-12
06:28:13",
"inarchive":0,
"active":1
,
"id":2462,
"name":"\u062a\u0628\u064a\u0636\u0627\u062a",
"img":null,
"haschild":1,
"parentid":1955,
"createdate":"2019-11-13 08:39:00",
"inarchive":0,
"active":1
,
"id":2464,
"name":"L12",
"img":null,
"haschild":0,
"parentid":1955,
"createdate":"2019-11-13
08:40:55",
"inarchive":0,
"active":1
,
"id":2488,
"name":"L13",
"img":null,
"haschild":0,
"parentid":1955,
"createdate":"2019-11-18 06:09:11",
"inarchive":0,
"active":1
,
"id":2490,
"name":"L14",
"img":null,
"haschild":0,
"parentid":1955,
"createdate":"2019-11-18 06:38:59",
"inarchive":0,
"active":1
,
"id":2491,
"name":"L15",
"img":null,
"haschild":0,
"parentid":1955,
"createdate":"2019-11-18
06:45:57",
"inarchive":0,
"active":1
,
"id":2497,
"name":"\u062a\u0644\u062e\u064a\u0635\u0627\u062a",
"img":null,
"haschild":1,
"parentid":1955,
"createdate":"2019-11-19 04:24:49",
"inarchive":0,
"active":1
,
"id":2509,
"name":"L16",
"img":null,
"haschild":0,
"parentid":1955,
"createdate":"2019-11-20
09:56:04",
"inarchive":0,
"active":1
,
"id":2522,
"name":"L17",
"img":null,
"haschild":0,
"parentid":1955,
"createdate":"2019-11-25 06:38:27",
"inarchive":0,
"active":1
,
"id":2542,
"name":"L18",
"img":null,
"haschild":0,
"parentid":1955,
"createdate":"2019-11-27 12:19:12",
"inarchive":0,
"active":1
,
"id":2552,
"name":"Protein
Lab",
"img":null,
"haschild":0,
"parentid":1955,
"createdate":"2019-11-27 16:32:27",
"inarchive":0,
"active":1
,
"id":2562,
"name":"Chromatography ",
"img":null,
"haschild":0,
"parentid":1955,
"createdate":"2019-11-30 15:24:24",
"inarchive":0,
"active":1
,
"id":2576,
"name":"L19",
"img":null,
"haschild":0,
"parentid":1955,
"createdate":"2019-12-02
02:05:29",
"inarchive":0,
"active":1
,
"id":2580,
"name":"L20",
"img":null,
"haschild":0,
"parentid":1955,
"createdate":"2019-12-02 08:23:48",
"inarchive":0,
"active":1
,
"id":2592,
"name":"21",
"img":null,
"haschild":0,
"parentid":1955,
"createdate":"2019-12-03 06:27:24",
"inarchive":0,
"active":1
,
"id":2600,
"name":"L22",
"img":null,
"haschild":0,
"parentid":1955,
"createdate":"2019-12-04
06:22:46",
"inarchive":0,
"active":1
,
"id":2614,
"name":"L23",
"img":null,
"haschild":0,
"parentid":1955,
"createdate":"2019-12-04 10:03:00",
"inarchive":0,
"active":1
,
"id":2640,
"name":"L24",
"img":null,
"haschild":0,
"parentid":1955,
"createdate":"2019-12-08 06:53:11",
"inarchive":0,
"active":1
,
"id":2644,
"name":"L25",
"img":null,
"haschild":0,
"parentid":1955,
"createdate":"2019-12-09
05:33:07",
"inarchive":0,
"active":1
,
"id":2649,
"name":"L26",
"img":null,
"haschild":0,
"parentid":1955,
"createdate":"2019-12-09 07:58:42",
"inarchive":0,
"active":1
,
"id":2711,
"name":"\u0623\u0633\u0626\u0644\u0629",
"img":null,
"haschild":0,
"parentid":1955,
"createdate":"2019-12-19
05:18:11",
"inarchive":0,
"active":1
],
"files":[
"id":4542,
"name":"Ch2-part1.m4a 27.52MB",
"img":null,
"uploader":"Aws",
"url":"http:\/\/msc-mu.com\/..\/uploaded\/031020190Ch2-part1.m4a",
"createdate":"2019-10-03 09:53:39",
"approved":1,
"active":1
]
【问题讨论】：
你能展示一下JSON 结构对于response.body 的样子吗？
你能指出代码吐出错误的那一行吗？
json 是地图，而不是 List错误来自这里：List<dynamic> data = json.decode(response.body);.
JSON 的body 是一个 json 对象（映射）。
json.decode(response.body) 将返回 Map，但您尝试为其分配 List 从而引发该错误。
你应该这样做：
if (response.statusCode == 200)
var data = json.decode(response.body);
return [FolderList.fromJson(data)];
else
throw Exception('We were not able to successfully download the Main Subjects.');
【讨论】：
没有工作它说我不能将return [FolderList.fromJson(data)];
iam rlly 抱歉，回复晚了，但你帮了我很多，现在表明 int 类型不是 string 类型的子类型
json 中的id 是int，但您的数据类接受String id。您应该 1) 将 String id 更改为 int id 或 2) 在您的 Data.fromJson 方法中使用 "$json['id']"
我可以和你不和吗？以上是关于Flutter - type '_InternalLinkedHashMap<String, dynamic> 不是 List<dynamic> 类型的子类型的主要内容，如果未能解决你的问题，请参考以下文章
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