Negozio: La schermata del carrello

Fa parte della sezione Progetti del percorso Flutter di Coddy. Lezione 23 di 36.

Il badge indica quanti articoli ci sono nel carrello. Toccandolo, dovrebbe mostrare quali sono, nella schermata del carrello.

Trasforma il badge in un pulsante: inserisci Badge all'interno di IconButton come suo icon e inserisci una CartScreen in onPressed. IconButton aggiunge 8 pixel di spazio attorno all'icona, quindi il padding a destra scende a 8.

La schermata del carrello non ha bisogno di dati nel costruttore: il carrello è già condiviso. Osserva il modello e crea una riga per ogni articolo:

final cart = context.watch<CartModel>();
...
for (Product product in cart.items)
  ListTile(
    leading: CircleAvatar(...),
    title: Text(product.name),
    trailing: Text(money.format(product.price)),
  ),

Questo è il punto di forza di un modello condiviso: la pagina del prodotto scrive nel carrello, la griglia e la schermata del carrello lo leggono e nessuna delle tre schermate passa dati alle altre.

Sfida

Medio

Mostra il carrello:

scrivi una CartScreen con una AppBar intitolata Your Cart e una ListView con una ListTile per ogni elemento nel carrello
ogni riga: una CircleAvatar nel shade50 del prodotto con la sua icona nel colore del prodotto, il nome e il prezzo come trailing
nella barra superiore della griglia, inserisci il Badge dentro un IconButton che apre CartScreen, a 8 pixel dal bordo destro

Provalo tu

import 'package:flutter/material.dart';
import 'package:intl/intl.dart';
import 'package:provider/provider.dart';

void main() {
  runApp(
    ChangeNotifierProvider(
      create: (context) => CartModel(),
      child: const MyApp(),
    ),
  );
}

final money = NumberFormat.currency(locale: 'en_US', symbol: '\$');

class MyApp extends StatelessWidget {
  const MyApp({super.key});

  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      debugShowCheckedModeBanner: false,
      theme: ThemeData(
        colorScheme: ColorScheme.fromSeed(seedColor: Colors.orange),
      ),
      home: const ShopScreen(),
    );
  }
}

class Product {
  const Product({
    required this.name,
    required this.price,
    required this.icon,
    required this.color,
    required this.description,
  });

  final String name;
  final double price;
  final IconData icon;
  final MaterialColor color;
  final String description;
}

const List<Product> products = [
  Product(
    name: 'Headphones',
    price: 59,
    icon: Icons.headphones,
    color: Colors.indigo,
    description: 'Wireless headphones with 30 hours of battery.',
  ),
  Product(
    name: 'Watch',
    price: 129,
    icon: Icons.watch,
    color: Colors.teal,
    description: 'A smart watch that counts your steps.',
  ),
  Product(
    name: 'Backpack',
    price: 45.5,
    icon: Icons.backpack,
    color: Colors.orange,
    description: 'Room for a laptop, a lunch and a jacket.',
  ),
  Product(
    name: 'Mug',
    price: 12,
    icon: Icons.coffee,
    color: Colors.brown,
    description: 'Holds a big coffee and keeps it warm.',
  ),
  Product(
    name: 'Camera',
    price: 1299,
    icon: Icons.photo_camera,
    color: Colors.blueGrey,
    description: 'A mirrorless camera for sharp photos.',
  ),
  Product(
    name: 'Sneakers',
    price: 89.99,
    icon: Icons.directions_run,
    color: Colors.red,
    description: 'Light running shoes for every day.',
  ),
];

class CartModel extends ChangeNotifier {
  final List<Product> _items = [];

  List<Product> get items => _items;
  int get count => _items.length;

  void add(Product product) {
    _items.add(product);
    notifyListeners();
  }
}

class ShopScreen extends StatelessWidget {
  const ShopScreen({super.key});

  @override
  Widget build(BuildContext context) {
    final count = context.watch<CartModel>().count;
    return Scaffold(
      appBar: AppBar(
        title: const Text('Coddy Shop'),
        actions: [
          Padding(
            padding: const EdgeInsets.only(right: 24),
            child: Badge(
              isLabelVisible: count > 0,
              label: Text('$count'),
              child: const Icon(Icons.shopping_cart),
            ),
          ),
        ],
      ),
      body: GridView.count(
        crossAxisCount: 2,
        padding: const EdgeInsets.all(16),
        mainAxisSpacing: 12,
        crossAxisSpacing: 12,
        childAspectRatio: 0.8,
        children: [
          for (Product product in products) ProductCard(product: product),
        ],
      ),
    );
  }
}

class ProductCard extends StatelessWidget {
  const ProductCard({super.key, required this.product});

  final Product product;

  @override
  Widget build(BuildContext context) {
    return Card(
      clipBehavior: Clip.antiAlias,
      child: InkWell(
        onTap: () {
          Navigator.push(
            context,
            MaterialPageRoute(
              builder: (context) => ProductScreen(product: product),
            ),
          );
        },
        child: Column(
          crossAxisAlignment: CrossAxisAlignment.start,
          children: [
            Expanded(
              child: Container(
                width: double.infinity,
                alignment: Alignment.center,
                color: product.color.shade50,
                child: Icon(product.icon, size: 56, color: product.color),
              ),
            ),
            Padding(
              padding: const EdgeInsets.all(12),
              child: Column(
                crossAxisAlignment: CrossAxisAlignment.start,
                children: [
                  Text(
                    product.name,
                    style: Theme.of(context).textTheme.titleMedium,
                  ),
                  const SizedBox(height: 4),
                  Text(
                    money.format(product.price),
                    style: TextStyle(
                      fontWeight: FontWeight.bold,
                      color: Theme.of(context).colorScheme.primary,
                    ),
                  ),
                ],
              ),
            ),
          ],
        ),
      ),
    );
  }
}

class ProductScreen extends StatelessWidget {
  const ProductScreen({super.key, required this.product});

  final Product product;

  @override
  Widget build(BuildContext context) {
    final textTheme = Theme.of(context).textTheme;
    return Scaffold(
      appBar: AppBar(title: Text(product.name)),
      body: ListView(
        padding: const EdgeInsets.all(24),
        children: [
          Container(
            height: 240,
            alignment: Alignment.center,
            decoration: BoxDecoration(
              color: product.color.shade50,
              borderRadius: BorderRadius.circular(24),
            ),
            child: Icon(product.icon, size: 120, color: product.color),
          ),
          const SizedBox(height: 24),
          Text(
            money.format(product.price),
            style: textTheme.headlineSmall?.copyWith(
              fontWeight: FontWeight.bold,
              color: Theme.of(context).colorScheme.primary,
            ),
          ),
          const SizedBox(height: 12),
          Text(product.description, style: textTheme.bodyLarge),
          const SizedBox(height: 32),
          FilledButton.icon(
            onPressed: () {
              context.read<CartModel>().add(product);
              ScaffoldMessenger.of(context).hideCurrentSnackBar();
              ScaffoldMessenger.of(context).showSnackBar(
                SnackBar(content: Text('Added ${product.name} to your cart')),
              );
            },
            icon: const Icon(Icons.add_shopping_cart),
            label: const Text('Add to cart'),
          ),
        ],
      ),
    );
  }
}