我的下拉列表是API的工作呼叫列表，并获取错误类型; _internallinkedHashmap＆lt; string，dynamic＆gt;＆gt;＆＃x27;不是类型的子类型。

Question

我正在尝试从REST API获取下拉列表，但是获得此错误例外：键入'_internallinkedhashmap＆lt; string，dynamic＆gt;'不是类型“列表”的子类型。如何解决此错误并在屏幕上获取我的原因列表。我的下拉无法正常工作。

 console screen:
 {Result: Success, Remarks: Records Found Successfully, data: [{reason: DOOR LOCKED}, {reason: 
 CUSTOMER NOT INTERESTED}, {reason: DEFECTIVE SPARES}, {reason: NO WATER SUPPLY TO CHECK}, 
{reason: PROBLEM NOT UNDERSTOOD}, {reason: NO ELECTRICITY WHEN VISITED                }, 
{reason: RESCHEDULED VISIT}, {reason: CUSTOMER UN-AWARE OF COMPLAINT LODGED}, {reason: SPARES 
UN-AVAILABLE DURING VISIT}, {reason: SPARES UN-AVAILABLE HENCE NOT VISITED}, {reason: CALL 
CLOSED BUT OPEN IN SYSTEM}]}
E/flutter (21266): [ERROR:flutter/lib/ui/ui_dart_state.cc(209)] Unhandled Exception: 
Exception: type '_InternalLinkedHashMap<String, dynamic>' is not a subtype of type 
'List<dynamic>'
E/flutter (21266): #0      CustomerDetailsOTCoPageState._getPendingRsn
package:zero_b/Options/customerdetailsOTCo_sp.dart:852
E/flutter (21266): <asynchronous suspension>
E/flutter (21266):

这是我的下拉按钮的主要课程。

 class CustomerDetailsOTCoPageState extends State<CustomerDetailsOTCoPage>
    with AutomaticKeepAliveClientMixin<CustomerDetailsOTCoPage> {
     final GlobalKey<ScaffoldState> _scaffoldKey = new GlobalKey<ScaffoldState>();

  List datalist = List();
  String selectedreason;

   @override
        void initState() {
            super.initState();
            this._getPendingRsn();
           }
  @override
     Widget build(BuildContext context) {
     return Scaffold(
           key: _scaffoldKey,
           body: WillPopScope(
            onWillPop: _onBackPressed,
             child: SingleChildScrollView(
                child: Container(
                  width: MediaQuery.of(context).size.width,
                  height: MediaQuery.of(context).size.height,
                  child: Column(children: <Widget>[
                    Container(
                     margin: EdgeInsets.only(
                       top: 2,
                       bottom: 4,
                       left: 8,
                       right: 8,
                     ),
                     padding: EdgeInsets.only(
                     top: 2,
                     bottom: 4,
                     left: 8,
                     right: 8,
                     ),
                  child: Row(children: <Widget>[
                  Text("Result :  ",
                  style: TextStyle(
                    fontFamily: "WorkSansMedium",
                    color: Colors.black,
                    fontSize: 15,
                  )),
                  DropdownButton<String>(
                    value: dropdownValue,
                    icon: Icon(Icons.arrow_drop_down),
                    iconSize: 19,
                    elevation: 14,
                  style: TextStyle(
                    color: Colors.black,
                    fontSize: 15,
                    fontFamily: "WorkSansMedium"),
                  onChanged: (String data) {
                  setState(() {
                    dropdownValue = data;
                  });
                },
                items: spinnerItems
                    .map<DropdownMenuItem<String>>((String value) {
                  return DropdownMenuItem<String>(
                    value: value,
                    child: Text(value),
                  );
                }).toList(),
              ),
            ]),
          ),
          dropdownValue == 'Pending'
              ? _dropdownPending()
              : Column(children: <Widget>[
                  FutureBuilder<Result>(
                    future: apiWorkComplete(),
                    builder: (context, snapshot) {
                      try {
                        if (snapshot.connectionState ==
                            ConnectionState.done) {
                          if (snapshot.hasError) {
                            return Container(
                              alignment: Alignment.center,
                              child: Text(
                                "Failed to load Page",
                                style: TextStyle(
                                    color: Colors.black,
                                    fontSize: 15.0,
                                    fontFamily: "WorkSansMedium"),
                              ),
                            );
                          } else if (snapshot.hasData &&
                              snapshot.data != null) {
                            return _workCompleteList(snapshot);
                          } else {
                            return Center(
                                child: Column(
                              children: <Widget>[
                                SizedBox(
                                  height: 100,
                                ),
                                CircularProgressIndicator(
                                  backgroundColor: Colors.white,
                                ),
                              ],
                            ));
                          }
                        } else {
                          return Center(
                              child: Column(
                            children: <Widget>[
                              SizedBox(
                                height: 100,
                              ),
                              CircularProgressIndicator(
                                backgroundColor: Colors.white,
                              ),
                            ],
                          ));
                        }
                      } catch (e) {
                        return Container(
                          alignment: Alignment.center,
                          child: Text(
                            "Failed to load Page!!",
                            style: TextStyle(
                                color: Colors.black,
                                fontSize: 15.0,
                                fontFamily: "WorkSansSemiBold"),
                          ),
                        );
                      }
                    },
                  ),
                  SizedBox(
                    height: 100,
                  )
                ]),
              ]),
             ),
           ));
     }

这是我的下拉小部件，它无法正常工作。 IT项目不映射。

  Widget _dropdownPending() => DropdownButton(
      icon: Icon(Icons.arrow_drop_down),
      iconSize: 19,
      elevation: 14,
      style: TextStyle(
        color: Colors.black54, fontSize: 19, fontFamily: "WorkSansMedium"),
      hint: Text(
       "Select Pending Reason",
       style: TextStyle(
          color: Colors.grey, fontSize: 15, fontFamily: "WorkSansMedium"),
    ),
    items: datalist.map((list) {
      debugger();
      return DropdownMenuItem(
        child: Text(list['reason']),
        value: list['reason'],
      );
    }).toList(),
    onChanged: (newVal) {
      setState(() {
        selectedreason = newVal;
      });
    },
    value: selectedreason,
   );

这是未来获得待处理原因的呼吁。该行可以正常工作。

  Future<String> _getPendingRsn() async {
   try {
    var url = Uri.parse(Constant.path + '/DSRTestV3/api_pndng_rsn');
    var response = await http.get(url);
  //  print(response.body);
  if (response.statusCode == 200) {
    var responseJson = json.decode(response.body);
    print(responseJson);
    setState(() {
      datalist = responseJson;
    });
    print(datalist);
    return responseJson;
   } else {
    throw Exception('Failed to load page');
   }
  }  catch (e) {
    throw Exception(e.toString());
   }
  }
 } 

这是获得待处理的原因项目的类。

 class Pend_rsnitem {
    final String reason;

 Pend_rsnitem({
    this.reason,
 });

 factory Pend_rsnitem.fromJson(Map<String, dynamic> json) {
   return Pend_rsnitem(
     reason: json['reason'],
  );
 }

 Map<String, dynamic> toJson(){
   final Map<String, dynamic> data = new Map<String, dynamic>();
   data['reason'] = this.reason;
   return data;
  }
}