shopping list with callbacks

main.dart

import 'package:flutter/material.dart';

typedef CartChangedCallback = void Function(Product product);
typedef CartDeleteCallback = void Function(Product product);

void main() {
  runApp(const MaterialApp(
    title: 'Shopping App',
    home: ShoppingList(),
  ));
}

class Product {
  Product({required this.inCart, required this.name});
  final String name;
  bool inCart;
}

class ShoppingListItem extends StatelessWidget {
  ShoppingListItem(
      {required this.product, required this.onCartChanged, this.onCartDelete})
      : super(key: ObjectKey(product));

  final Product product;
  final CartChangedCallback onCartChanged;
  final CartDeleteCallback? onCartDelete;

  Color _getColor(BuildContext context) {
    return product.inCart //
        ? Colors.black54
        : Theme.of(context).primaryColor;
  }

  TextStyle? _getTextStyle(BuildContext context) {
    if (!product.inCart) return null;

    return const TextStyle(
      color: Colors.black54,
      decoration: TextDecoration.lineThrough,
    );
  }

  @override
  Widget build(BuildContext context) {
    return ListTile(
      onLongPress: () {
        onCartDelete!(product);
      },
      onTap: () {
        onCartChanged(product);
      },
      leading: CircleAvatar(
        backgroundColor: _getColor(context),
        child: Text(product.name[0]),
      ),
      title: Text(product.name, style: _getTextStyle(context)),
    );
  }
}

class ShoppingList extends StatefulWidget {
  const ShoppingList({super.key});
  @override
  _ShoppingListState createState() => _ShoppingListState();
}

class _ShoppingListState extends State<ShoppingList> {
  List<Product> products = List<Product>.empty(growable: true);
  final TextEditingController _textFieldController = TextEditingController();
  
  late String valueText;

  void _handleCartChanged(Product product) async {
    setState(() {
      if (!product.inCart) {
        product.inCart = true;
      } else {
        product.inCart = false;
      }
    });
  }

  void _handleCartDelete(Product product) {
    showDialog(
        context: context,
        builder: (context) {
          return AlertDialog(
              title: const Text('Attention'),
              content: const Text('Do you want to delete the item?'),
              actions: <Widget>[
                TextButton(
                  style: TextButton.styleFrom(
                    foregroundColor: Colors.red,
                  ),
                  child: const Text('CANCEL'),
                  onPressed: () {
                    setState(() {
                      Navigator.pop(context);
                    });
                  },
                ),
                TextButton(
                  child: const Text('YES'),
                  onPressed: () async {
                    products.removeWhere((item) => item.name == product.name);
                    setState(() {
                      Navigator.pop(context);
                    });
                  },
                ),
              ]);
        });
  }

  void _addProduct(BuildContext context) async {
    return showDialog(
        context: context,
        builder: (context) {
          return AlertDialog(
            title: const Text('Item'),
            content: TextField(
              onChanged: (value) {
                setState(() {
                  valueText = value;
                });
              },
              controller: _textFieldController,
              decoration: const InputDecoration(hintText: "Add"),
            ),
            actions: <Widget>[
              TextButton(
                style: TextButton.styleFrom(
                  foregroundColor: Colors.red,
                ),
                child: const Text('CANCEL'),
                onPressed: () {
                  setState(() {
                    _textFieldController.clear();
                    Navigator.pop(context);
                  });
                },
              ),
              TextButton(
                child: const Text('OK'),
                onPressed: () async {
                  products.add(Product(inCart: true, name: valueText));
                  _handleCartChanged(products.last);
                  setState(() {
                    _textFieldController.clear();
                    Navigator.pop(context);
                  });
                },
              ),
            ],
          );
        });
  }

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: const Text('Shopping List'),
      ),
      body: ListView.builder(
          itemCount: products.length,
          itemBuilder: (context, index) {
            return ShoppingListItem(
              product: products[index],
              onCartChanged: _handleCartChanged,
              onCartDelete: _handleCartDelete,
            );
          }),
      floatingActionButton: FloatingActionButton(
        onPressed: () => _addProduct(context),
        tooltip: 'Add',
        child: const Icon(Icons.add),
      ),
    );
  }
}