输入&#39;未来<List<Data> &gt;&#39; 不是 &#39;List 类型的子类型<Data> &#39; 在类型转换中

Question

I am getting the data from server and trying to set it in a grid view but I am getting error:

type 'Future<List<Data>>' is not a subtype of type 'List<Data>' in type cast

Here is my Data Class:

class Data with ChangeNotifier {
Data({
  this.name,
  this.image,
});

final String image;
final String name;


factory Data.fromJson(Map<String, dynamic> json) {
print(json['title'].toString());
return Data(
  name: json['title'].toString(),
  image: json['image'].toString(),
 );

}
}

And this is my Data_screen where I am calling this:

 var datas= Provider.of<Datas>(context).fetchData() as List<Data>;
 var datalength = datas.length;

Widget:

 Expanded(
            child: GridView.builder(
              gridDelegate: SliverGridDelegateWithFixedCrossAxisCount(

                crossAxisSpacing: 10,
                mainAxisSpacing: 10,
              ),
              padding: EdgeInsets.only(left: 28, right: 28, bottom: 58),
              itemCount: datas.length,

              itemBuilder: (context, index) => DataCard(
                datas[index],
                index: index,
                onPress: () {
                },
              ),
            ),
          ),

And in Datas.dart:

 Future<List<Data>> fetchData() async {
 var response = await http.get(url);
 var responseJson = json.decode(response.body);
 print(responseJson);
 return (responseJson['datas'])
    .map<Data>((p) => Data.fromJson(p))
  .toList();

}

Answer 1

The message is so clear. You cannot cast from List<Data> to Future<List<Data>> . Try to use:

List<Data> fetchData() async {
 var response = await http.get(url);
 var responseJson = json.decode(response.body);
 print(responseJson);
 return (responseJson['datas'])
    .map<Data>((p) => Data.fromJson(p))
  .toList();
}

OR return a new Future with the List<Data>

Future<List<Data>> fetchData() async {
 var response = await http.get(url);
 var responseJson = json.decode(response.body);
 print(responseJson);
 var response = (responseJson['datas'])
    .map<Data>((p) => Data.fromJson(p))
  .toList();
 return Future.value(response)
}

It just an idea(without testing)