How to correctly pass IconData as and argument to a custom widget-CodePudding

I have a custom wrapper around the TextFormField widget, I want to be able to pass in a material Icon as an argument to the constructor. However, when trying to pass the IconData into the Icon constructor I get an error: Arguments of constant creation must be constant expressions.

import 'package:flutter/material.dart';

class LoginFormField extends StatelessWidget {
   const LoginFormField({Key? key,
    required this.fillColor,
    required this.textColor,
    required this.borderColor,
    required this.onChanged,
    required this.validateField,
    required this.icon
  }) : super(key: key);

  final Color fillColor;
  final Color textColor;
  final Color borderColor;
  final Function(String) onChanged;
  final FormFieldValidator validateField;
  final IconData icon;

  @override
  Widget build(BuildContext context) {
    return TextFormField(
      decoration: InputDecoration(
        fillColor: fillColor,
        border: OutlineInputBorder(
          borderRadius: BorderRadius.circular(8),
          borderSide: BorderSide(width: 16, color: borderColor)
        ),
        labelText: 'Enter your username',
        prefixIcon: const Padding(
          padding: EdgeInsets.only(top: 15), // add padding to adjust icon
          child: Icon(icon)
        ),
      ),
      validator: validateField,
      onChanged: onChanged,
    );
  }
}

Any help on how to correctly pass in an icon as an argument?

CodePudding user response：

You're passing icondata correctly. The error is telling you the that prefixicon can not be const.

prefixIcon: const Padding(
  padding: EdgeInsets.only(top: 15), // add padding to adjust icon
  child: Icon(icon)
),

Remove the const as icon is argument to your widget which is not const. Make it

prefixIcon: Padding(
  padding: EdgeInsets.only(top: 15), // add padding to adjust icon
  child: Icon(icon)
),

CodePudding user response：

It is because you're setting the widget as const.

Remove const from the following code:

prefixIcon: const Padding(
  padding: EdgeInsets.only(top: 15), // add padding to adjust icon
  child: Icon(icon)
),

it becomes:

prefixIcon: Padding(
  padding: EdgeInsets.only(top: 15), // add padding to adjust icon
  child: Icon(icon)
),