_ TypeError（类型'bool'不是类型'String'的子类型）

Question

pic请帮我解决这个错误，我到处都在寻找解决方案，但是它无法解决！！

Future<UserModel> createUser(String id, String trangthaiapp, String giatriapp) async{

final response = await http.post(apiUrl, headers: headers,
body: json.encode({
"id_machdien": id,
"trang_thaiapp": trangthaiapp,
"giatri_app:": giatriapp,
})
);

if(response.statusCode == 200){
final String responseString = response.body;

return userModelFromJson(responseString);
}else{
return null;
}
}
class _MyHomePageState extends State<MyHomePage> {

 UserModel _user;
 @override
  Widget build(BuildContext context) {

    return MaterialApp(
      home: Scaffold(
        appBar: AppBar(

        title: Text(widget.title),
        ),
        body:Center(
          child: Column(
            children: <Widget> [ 
              RaisedButton(
                onPressed: () async{
                  final String id = "333";
                  final String trangthaiapp = "true";
                  final String giatriapp= "true";
                  final UserModel user = await createUser(id, trangthaiapp, giatriapp);

                  setState(() {
                    _user = user;
                  });
                },
              ),
                    RaisedButton(
                onPressed: () async{
                  final String id = "333";
                  final String trangthaiapp = "false";
                  final String giatriapp= "false";
                  final UserModel user = await createUser(id, trangthaiapp, giatriapp);
                  setState(() {
                    _user = user;
                  });
                  },
              ),
            ],
          ),
        ),
      )
    );
}
 }

关于类user_model.dart

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 import 'dart:convert';

  UserModel userModelFromJson(String str) => UserModel.fromJson(json.decode(str));

  String userModelToJson(UserModel data) => json.encode(data.toJson());

  class UserModel {
  String id;
  String trangthaiapp;
  String giatriapp;


   UserModel({
   this.id,
   this.trangthaiapp,
    this.giatriapp,

    });

    factory UserModel.fromJson(Map<String, dynamic> json) {
    var userModel = UserModel(
    id: json["id_machdien"],
    trangthaiapp: json["trang_thaiapp"],
    giatriapp: json["giatri_app"],

    );
    return userModel;
      }

      Map<String, dynamic> toJson() => {
      "id_machdien": id,
       "trang_thaiapp": trangthaiapp,
        "giatri_app": giatriapp,

       };
         }
    

pic请帮助我解决这个错误，我到处都在寻找解决方案，但无法解决！！！ Future createUser（String id，String trangthaiapp，String giatriapp）async {final ...

Answer 1

String id;
bool trangthaiapp;
String giatriapp;