Flutter 3: Invalid constant value. on onPressed value from another file, component

I’m very new to flutter I started Yesterday it seems easy but am stuck on using a component I created for CustomButtons

Here is my code.
CustomButtons components

import 'package:flutter/material.dart';

class CustomButton extends StatelessWidget {
  const CustomButton({
    Key? key,
    required this.child,
    this.outlineColor = Colors.transparent,
    this.bgColor = const Color.fromARGB(39, 59, 148, 240),
    this.btnVPadding = 14.0,
    required this.onPressed,
    this.buttonType = '',
  }) : super(key: key);

  final Widget child;
  final Color outlineColor;
  final Color bgColor;
  final double btnVPadding;
  final VoidCallback? onPressed;
  final String buttonType;

  @override
  Widget build(BuildContext context) {
    if (buttonType == 'OutlinedButton') {
      return OutlinedButton(
        style: OutlinedButton.styleFrom(
          backgroundColor: bgColor,
          padding: EdgeInsets.symmetric(vertical: btnVPadding),
          side: BorderSide(
            color: outlineColor,
          ),
        ),
        onPressed: onPressed,
        child: child,
      );
    }

    return ElevatedButton(
      style: ElevatedButton.styleFrom(
        backgroundColor: bgColor,
        padding: EdgeInsets.symmetric(vertical: btnVPadding),
        elevation: 0,
      ),
      onPressed: onPressed,
      child: child,
    );
  }
}

And I call this class here..

import 'package:flutter/material.dart';
import 'package:util_app/components/buttons/button.dart';

class SignUp extends StatelessWidget {
  const SignUp({Key? key}) : super(key: key);

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: const Text("Manage your Utilities"),
        centerTitle: true,
        elevation: 2.0,
      ),
      body: _buildContent(),
    );
  }

  Widget _buildContent() {
    return Container(
      color: const Color.fromARGB(255, 255, 255, 255),
      padding: const EdgeInsets.all(16.0),
      child: Column(
        mainAxisAlignment: MainAxisAlignment.center,
        crossAxisAlignment: CrossAxisAlignment.stretch,
        children: const <Widget>[
          Text(
            "Sign In",
            textAlign: TextAlign.center,
            style: TextStyle(
              fontSize: 32.0,
              fontWeight: FontWeight.w600,
            ),
          ),
          SizedBox(height: 8.0),
          CustomButton(
            buttonType: '',
            // the problem is here..
            onPressed: () {},
            child: Text(
              "LOGIN",
              style: TextStyle(
                color: Colors.white,
                fontSize: 16.0,
              ),
            ),
          )
          // button test
        ],
      ),
    );
  }
}

I get this error message

Invalid constant value.dart(invalid_constant)
The values in a const list literal must be constants.
Try removing the keyword ‘const’ from the list literal.dartnon_constant_list_element

I search and found this answer but it didn’t help I tried most of the solutions provided but still nothing.

>Solution :

You can’t use children: const <Widget>[ because CustomButton onPressed: () {}, will trigger on runtime. Remove this const from SignUp class Column

class SignUp extends StatelessWidget {
  const SignUp({Key? key}) : super(key: key);

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: const Text("Manage your Utilities"),
        centerTitle: true,
        elevation: 2.0,
      ),
      body: _buildContent(),
    );
  }

  Widget _buildContent() {
    return Container(
      color: const Color.fromARGB(255, 255, 255, 255),
      padding: const EdgeInsets.all(16.0),
      child: Column(
        mainAxisAlignment: MainAxisAlignment.center,
        crossAxisAlignment: CrossAxisAlignment.stretch,
        children:   <Widget>[
          Text(
            "Sign In",
            textAlign: TextAlign.center,
            style: TextStyle(
              fontSize: 32.0,
              fontWeight: FontWeight.w600,
            ),
          ),
          SizedBox(height: 8.0),
          CustomButton(
            buttonType: '',
            onPressed: () {},
            child: Text(
              "LOGIN",
              style: TextStyle(
                color: Colors.white,
                fontSize: 16.0,
              ),
            ),
          )
          // button test
        ],
      ),
    );
  }
}