The parameter 'colour' can't have a value of 'null' because of its type, but the implicit default value is 'null'

Issue

enter image description here

code here constructor's this.colour vairable does not work

class ReusableCard extends StatelessWidget {
  Color colour= null;
  ReusableCard({@required this.colour});
  @override
  Widget build(BuildContext context) {
    return Container(
      margin: EdgeInsets.all(15),
      decoration: BoxDecoration(
        color: colour,
        borderRadius: BorderRadius.circular(10.0),
      ),
    );
  }
}

Solution

This code should solve your problem:

ReusableCard({this.colour}); 
Color? colour;

Because Color isnt assigned yet it can be null. Dart has nullsafety so the question mark implies the value can be null. See this link for more details: https://sanjibsinha.com/null-safety-in-flutter-dart/

Edit: you could also do it like this:

ReusableCard({this.colour}); 
late Color colour;

The late keyword to initialize a variable when it is first read, rather than when it's created

Answered By - EnviroApps