Question

我遇到了类似的错误未处理的异常：类型'（dynamic）=> Null'不是'f'类型的'（String，dynamic）=> void'的子类型

我正在从api接收事件的数据列表，该列表将显示在下面

{events: [
{
    _id: 5eac064141cd6224343f2bb8, 
    titleOfTheEvent: asdasd, 
    startingDateOfTheEvent: 2020-05-03 00:00:00.000, 
    endingDateOfTheEvent: 2020-05-04 00:00:00.000, 
    industry: dasdas, 
    venue: sadasdd, 
    numberOfStalls: 2, 
    stallBookingContactNumber: 9087654321, 
    description: sdasdasd, 
    creatorOfTheEvent: 5e8f15c22f955416f85ae7eb, 
    createdAt: 2020-05-01T11:21:37.244Z, 
    updatedAt: 2020-05-01T11:21:37.244Z,
     __v: 0
},  
{
    _id: 5eac0a0ddd0bb6474428dd21, 
    titleOfTheEvent: Worl something day, 
    startingDateOfTheEvent: 2020-05-02 00:00:00.000, 
    endingDateOfTheEvent: 2020-05-04 00:00:00.000, 
    industry: Automobile, 
    venue: Bangalore, 
    numberOfStalls: 5, 
    stallBookingContactNumber: 9087654321, 
    description: asd, 
    creatorOfTheEvent: 5e8f15c22f955416f85ae7eb, 
    createdAt: 2020-05-01T11:37:49.816Z, 
    updatedAt: 2020-05-01T11:37:49.816Z,
     __v: 0
}]
}

我试图将其设置为显示数据，但出现错误

  Future<void> fetchAndSetEvents() async{
const url ='http://10.0.2.2:8080/event/events';
try{
  final response = await http.get(url);
  final extractedData = json.decode(response.body) as Map<String, dynamic>;
  if(extractedData == null){
    return;
  }
  final List<Event> loadedEvents =[];
  extractedData.forEach((eventData){
    loadedEvents.add(Event(
    id:eventData['_id'],
    title:eventData['titleOfTheEvent'],
    eventStartDate:eventData['startingDateOfTheEvent'],
    eventEndDate:eventData['endingDateOfTheEvent'],
    venue:eventData['industry'],
    industry:eventData['venue'],
    numberOfStalls:eventData['numberOfStalls'],
    contactNumber:eventData['stallBookingContactNumber'],
    description:eventData['description'],
    ));
  });
  _events = loadedEvents;
  notifyListeners();
}catch(error){
  print(error);
  throw(error);
}
}

我从有状态的小部件中调用函数

  @override
  void didChangeDependencies() {
  if(_isInit){
  setState(() {
    _isLoading = true;
  });
  Provider.of<Events>(context).fetchAndSetEvents().then((_){
    setState(() {
      _isLoading=false;
    });
   });
   }
   _isInit=false;
   super.didChangeDependencies();
   }

我得到的堆栈跟踪是

E/flutter ( 7567): [ERROR:flutter/lib/ui/ui_dart_state.cc(157)] Unhandled 
Exception: type '(dynamic) => Null' is not a subtype of type '(String,                 
dynamic) => void' of 'f'
E/flutter ( 7567): #0      Events.fetchAndSetEvents 
package:scopemobileapp/providers/events.dart:57
E/flutter ( 7567): <asynchronous suspension>
E/flutter ( 7567): #1      _ProducerAllProjectsState.didChangeDependencies 
package:scopemobileapp/…/producer/producer_projects.dart:36
E/flutter ( 7567): #2      StatefulElement._firstBuild 
package:flutter/…/widgets/framework.dart:4376
E/flutter ( 7567): #3      ComponentElement.mount 
package:flutter/…/widgets/framework.dart:4201
E/flutter ( 7567): #4      Element.inflateWidget 
package:flutter/…/widgets/framework.dart:3194
E/flutter ( 7567): #5      Element.updateChild 
package:flutter/…/widgets/framework.dart:2988
E/flutter ( 7567): #6      SingleChildRenderObjectElement.mount 
package:flutter/…/widgets/framework.dart:5445
E/flutter ( 7567): #7      Element.inflateWidget 
package:flutter/…/widgets/framework.dart:3194
E/flutter ( 7567): #8      Element.updateChild 
package:flutter/…/widgets/framework.dart:2988
E/flutter ( 7567): #9      ComponentElement.performRebuild 
package:flutter/…/widgets/framework.dart:4243
E/flutter ( 7567): #10     Element.rebuild 
package:flutter/…/widgets/framework.dart:3947
E/flutter ( 7567): #11     ComponentElement._firstBuild package:flutter/ 
…/widgets/framework.dart:4206
E/flutter ( 7567): #12     ComponentElement.mount 
package:flutter/…/widgets/framework.dart:4201
E/flutter ( 7567): #13     Element.inflateWidget 
package:flutter/…/widgets/framework.dart:3194
E/flutter ( 7567): #14     Element.updateChild 
package:flutter/…/widgets/framework.dart:2988
E/flutter ( 7567): #15     SingleChildRenderObjectElement.mount 
package:flutter/…/widgets/framework.dart:5445
E/flutter ( 7567): #16     Element.inflateWidget 
package:flutter/…/widgets/framework.dart:3194
E/flutter ( 7567): #17     Element.updateChild 
package:flutter/…/widgets/framework.dart:2988
E/flutter ( 7567): #18     SingleChildRenderObjectElement.mount 
package:flutter/…/widgets/framework.dart:5445
E/flutter ( 7567): #19     Element.inflateWidget 
package:flutter/…/widgets/framework.dart:3194
E/flutter ( 7567): #20     Element.updateChild 
package:flutter/…/widgets/framework.dart:2988
E/flutter ( 7567): #21     ComponentElement.performRebuild 
package:flutter/…/widgets/framework.dart:4243
E/flutter ( 7567): #22     Element.rebuild 
package:flutter/…/widgets/framework.dart:3947
E/flutter ( 7567): #23     ComponentElement._firstBuild 
package:flutter/…/widgets/framework.dart:4206
E/flutter ( 7567): #24     StatefulElement._firstBuild 
package:flutter/…/widgets/framework.dart:4381
E/flutter ( 7567): #25     ComponentElement.mount 
package:flutter/…/widgets/framework.dart:4201
E/flutter ( 7567): #26     Element.inflateWidget 
package:flutter/…/widgets/framework.dart:3194
E/flutter ( 7567): #27     Element.updateChild 
package:flutter/…/widgets/framework.dart:2988
E/flutter ( 7567): #28     SingleChildRenderObjectElement.mount 
package:flutter/…/widgets/framework.dart:5445
E/flutter ( 7567): #29     Element.inflateWidget 
package:flutter/…/widgets/framework.dart:3194
E/flutter ( 7567): #30     Element.updateChild 
package:flutter/…/widgets/framework.dart:2988
E/flutter ( 7567): #31     SingleChildRenderObjectElement.mount 
package:flutter/…/widgets/framework.dart:5445
E/flutter ( 7567): #32     Element.inflateWidget 
package:flutter/…/widgets/framework.dart:3194
E/flutter ( 7567): #33     Element.updateChild 
package:flutter/…/widgets/framework.dart:2988
E/flutter ( 7567): #34     ComponentElement.performRebuild 
package:flutter/…/widgets/framework.dart:4243
E/flutter ( 7567): #35     Element.rebuild 
package:flutter/…/widgets/framework.dart:3947
E/flutter ( 7567): #36     ComponentElement._firstBuild 
package:flutter/…/widgets/framework.dart:4206
E/flutter ( 7567): #37     StatefulElement._firstBuild 
package:flutter/…/widgets/framework.dart:4381
E/flutter ( 7567): #38     ComponentElement.mount 
package:flutter/…/widgets/framework.dart:4201
E/flutter ( 7567): #39     Element.inflateWidget 
package:flutter/…/widgets/framework.dart:3194
E/flutter ( 7567): #40     Element.updateChild 
package:flutter/…/widgets/framework.dart:2988
E/flutter ( 7567): #41     ComponentElement.performRebuild 
package:flutter/…/widgets/framework.dart:4243
E/flutter ( 7567): #42     Element.rebuild 
package:flutter/…/widgets/framework.dart:3947
E/flutter ( 7567): #43     ComponentElement._firstBuild

未处理的异常：类型'（dynamic）=> Null'不是'f'类型'（String，dynamic）=> void'的子类型

0 个答案: