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

Question

i dont know why i am getting the errors,i have previously coded the same and it worked perfectly fine maybe some new update or plugin please help me solve my error

import 'package:flutter/material.dart';

class RoundedButton extends StatelessWidget {
  final String title;
  final Color colour;
  final Function onPressed;
  RoundedButton({this.title, this.colour, @required this.onPressed});

  @override
  Widget build(BuildContext context) {
    return Padding(
      padding: EdgeInsets.symmetric(vertical: 16.0),
      child: Material(
        elevation: 5.0,
        color: colour,
        borderRadius: BorderRadius.circular(30.0),
        child: MaterialButton(
          onPressed: onPressed,
          minWidth: 200.0,
          height: 42.0,
          child: Text(
            title,
            style: TextStyle(color: Colors.white),
          ),
        ),
      ),
    );
  }
}

Solution

As said also in the previous anwser:

1. Change the @required => required
2. Add '?' to potentially nullable variable
3. Add default value

In your case maybe I'll use something like this:

final String title;
final Color colour;
final VoidCallBack? onPressed;

RoundedButton({
    required this.title,
    this.colour = Colors.blue,
    this.onPressed,
});

Because the title can't be null, the colour can be the default one and the onPress can be empty for future implementation of your app.