Error: The argument type 'Function?' can't be assigned to the parameter type 'void Function(bool?)?'

Question

i get Error: The argument type 'Function?' can't be assigned to the parameter type 'void Function(bool?)?'. when i try to change toggle status of my checkbox how can i solve this problem?

itemCard

import 'package:flutter/material.dart';

class ItemCard extends StatelessWidget {
  final String title;
  final bool isDone;
  final Function toggleStatus;//toggle status
  const ItemCard(
      {Key? key,
      required this.title,
      required this.isDone,
      required this.toggleStatus})
      : super(key: key);

  @override
  Widget build(BuildContext context) {
    return Card(
        elevation: 5,
        shadowColor: Theme.of(context).primaryColor,
        shape: RoundedRectangleBorder(borderRadius: BorderRadius.circular(20)),
        child: ListTile(
          title: Text(
            title,
            style: TextStyle(color: Colors.black),
          ),
          trailing: Checkbox(
            value: isDone,
            activeColor: Colors.green,
            onChanged: toggleStatus,//ERROR
          ),
        ));
  }
}``

item

class Item {
  final String title;
  bool isDone;
  Item({required this.title, this.isDone = false});

  void toggleStatus() {
    isDone = !isDone;
  }
}

Solution 1

All function types have the base type Function. This can include something as benign as void Function() or as complex as Future<Map<String, dynamic>> Function(int, int, String, MyClass, List<int>). Your code is complaining because the onChanged property of a Checkbox must be void Function(bool), but you are passing in a value that is just Function, which could be literally any kind of function.

You need to change the type of toggleStatus in your class declaration from Function to void Function(bool):

final void Function(bool) toggleStatus;

This means you need to change the signature of toggleStatus in your item class as well:

void toggleStatus(bool status) {
  isDone = status;
}

Solution 2

Replace onChanged: toggleStatus, with onChanged: (v) => toggleStatus(v).

Or final Function toggleStatus; with final Function(bool?) toggleStatus;

Comments

[Vedat]

Thank you it works now