Why do I get this error: _CastError (Null check operator used on a null value)

I have a column like this:

  Column(children: [
    product.videos![product.videoIndex].videoUrl != null &&
            product.videos![product.videoIndex].videoUrl != ""
        ? VideoPlayerWidget(
            videoAddress: product.videos![product.videoIndex].videoUrl)
        : Image.asset('assets/images/video-placeholder.jpg'),
  ]),

And I get this error:

_CastError (Null check operator used on a null value)

I know that the variables may be null and that's the reason I put them within a null check if statement, but I don't know why do I get the null check error and how can I pass that?

The Flutter forced me to put ! after null variables, then it gives me error because of that!

It is because product.videos is null, though you handled the condition if it is null, but you are assuring dart compiler that product.videos can nver be null , by using ! opeartor. Change ! to ? meaning , it may be subjected to being null, and precautions would be taken if it is null.

Change your code by replacing ! to ?:

 product.videos?[product.videoIndex].videoUrl != null &&
            product.videos?[product.videoIndex].videoUrl != ""
        ? VideoPlayerWidget(
            videoAddress: product.videos![product.videoIndex].videoUrl)
        : Image.asset('assets/images/video-placeholder.jpg'),

Edit for the comment:

Could you explain what is the difference between ! and ?. and ? and ??

1. ! - Saying the compiler value can never be null.

var val1 = val2! // val2 can never be null

2. ? - Saying the compiler value can be null.

String? val; // Here val can be potentially null

3. ?. - Access only if not null.

object?.prop1; // Here prop1 is accessed only if object is not null

4. ?? - Alternate value if the value is null

var val1 = val2 ?? val3; // if val2 is null assign va13 to val1