Null check operator used on a null value?

Question

**======== Exception caught by widgets library ======================================================= The following _CastError was thrown building Builder: Null check operator used on a null value **

productmodel.dart
  final List? size;

main.dart
final Product? product;
List _sizeList=[];

`if(widget.product.size!.isNotEmpty){`
`_sizeList=widget.product.size!;`
`}`
       Container(
                                height: 80,
                                child: ListView.builder(
                                    scrollDirection: Axis.horizontal,
                                itemCount: _sizeList!.length,
                                  itemBuilder: (context,index){
                                    print(_sizeList![index]);
                                    return Text(_sizeList![index]);
                                }),
                              ),

Give a little more context. From your snippet, it looks like size might return null. Try if(widget.product.size != null){ _sizeList=widget.product.size!; } — Marcos Maliki, Mar 22 '22 at 19:08
can you show us how you're feeding the **product** into the widget? — Roman Jaquez, Mar 22 '22 at 19:28
this question already answered [here](https://stackoverflow.com/questions/64278595/null-check-operator-used-on-a-null-value) — Faiz Ahmad Dae, Mar 23 '22 at 06:37

score 1 · Answer 1 · answered Mar 22 '22 at 20:42

1

You use null-assertion operator (1). For example here:

`if(widget.product.size!.isNotEmpty){`

It means, that you are sure, that property size isn't null. But in some place in your code variable appears to be null, and you have corresponding error

answered Mar 22 '22 at 20:42

Liliia

71
3

I know that problem but i have no solutions – ali ALI Mar 23 '22 at 05:27

Null check operator used on a null value?

1 Answers1