So I am switching a project to flutter null safety but i am getting Null check operator used on a null value error i tried looking into other similar issue tried but its not working for me the complete error is as following
The following _CastError was thrown building HomeBanner(dirty, dependencies: [MediaQuery, _InheritedProviderScope<HomeViewModel>], state: _HomeBannerState#2de56):
Null check operator used on a null value
The relevant error-causing widget was:
HomeBanner file:///D:/fabricoMAt/lib/ui/views/home_screen.dart:26:17
When the exception was thrown, this was the stack:
#0 HomeViewModel.initData (package:knoty/business_logic/view_models/home_viewmodel.dart:25:33)
#1 _HomeBannerState._getImageSliders (package:knoty/ui/widgets/home_banner.dart:30:18)
#2 _HomeBannerState.build (package:knoty/ui/widgets/home_banner.dart:20:23)
#3 StatefulElement.build (package:flutter/src/widgets/framework.dart:4612:27)
#4 ComponentElement.performRebuild (package:flutter/src/widgets/framework.dart:4495:15)
...
====================================================================================================
======== Exception caught by widgets library =======================================================
Null check operator used on a null value
The relevant error-causing widget was:
WhomeServices file:///D:/fabricoMAt/lib/ui/views/home_screen.dart:43:17
And so onn this is coming at multiple place and i am not getting any idea how to fix this.
HomeViewModel model = Provider.of<HomeViewModel>(context);
Size screenSize = MediaQuery.of(context).size;
return model.initData == null //home_banner line 30
? [1, 2, 3, 4]
.map(
(item) => Shimmer.fromColors(
child: Container(
margin: EdgeInsets.only(right: 8),
width: screenSize.width * .7,
height: screenSize.width * .35,
decoration: BoxDecoration(
borderRadius: BorderRadius.all(
Radius.circular(8.0),
),
color: Colors.black,
),
),
baseColor: Colors.grey.shade300,
highlightColor: Colors.grey.shade100,
),
)
.toList()
the other mentioned line
Init? _initData;
City get selectedCity {
return _initData!.cities
.firstWhere((element) => element.id == _initData!.selectedCityId);
}
Init get initData => _initData!;// home_viewmodel.dart 25
In home_banner
at line 30, you are using initData
method which returns a not nullable value.
So make a nullable return type of initData
and remove !
from _initData
.
Init? get initData => _initData;// home_viewmodel.dart 25
And if you are using get selectedCity
in your code without checking the null value of _initData
, this may cause an error in your code, So add a null check in this method also.
City get selectedCity {
City? city = _initData?.cities
.firstWhere((element) => element.id == _initData?.selectedCityId);
if(city==null){
return City();// return default city
}else{
return city;
}
}
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