I have made a BMI calculator in flutter. I am new in flutter. After running the code i am receiving the above warning. Kindly provide me the solution of this problem. Below attached is the link of the code

Link of the dart file

CodePudding user response：

You are declaring the _result variable as non-nullable,

 late double _result;

However you do a null check

null == _result ? "Enter Value" : _result.toStringAsFixed(2),

So change your variable declaration to this,

double? _result;

And then you can null check this way

 _result?.toStringAsFixed(2) ?? "Enter Value" ,

CodePudding user response：

You declared the result variable like this:

late double _result;

_result is the name of the variable, double is the type.

late means you are not yet assigning a value to it.

A late variable is different from a nullable variable in the sense that a nullable variable's value could be null, a late variable doesn't have a value until you assign one.

late int xd;

if (xd == null) {
}

the above if will always be false because xd's value is not null, xd has no value at all.

a nullable variable is determined with a ? after the type:

double? _result;

which means that if you haven't assigned anything to it, it will be null, but you can also assign null directly.

_result = null;

the above is not possible for a late variable.