Toko: Total

Termasuk bagian Proyek dalam perjalanan Flutter di Coddy. Pelajaran 24 dari 36.

Sebelum membayar, kamu ingin tahu satu angka: totalnya. Total dihitung dari item-item di model, seperti jumlahnya:

double get total => _items.fold(0, (sum, product) => sum + product.price);

fold menelusuri list sambil menyimpan nilai sementara. Prosesnya dimulai dari 0, lalu untuk setiap product, proses ini memberikan nilai sejauh ini, yaitu sum, dan product tersebut kepadamu. Nilai yang kamu kembalikan menjadi sum berikutnya. Setelah product terakhir, hasilnya adalah total.

Tampilkan total di bagian bawah layar keranjang, tempat tombol checkout berada di aplikasi belanja. bottomNavigationBar pada Scaffold adalah widget apa pun yang ditempatkan di bagian bawah. Bungkus dengan SafeArea agar tidak tertutup bilah beranda ponsel. Di dalamnya, Row dengan Spacer mendorong jumlah ke ujung kanan.

Total menggunakan formatter money yang sama seperti harga lainnya, sehingga tampilannya serupa.

Tantangan

Sedang

Tampilkan total:

tambahkan getter total ke CartModel
beri Scaffold keranjang properti bottomNavigationBar: SafeArea yang menampung padding 16 piksel di sekeliling Row berisi Total, Spacer, dan total yang sudah diformat
gunakan titleLarge dari tema untuk kedua teks, dan tebalkan juga jumlahnya

Coba sendiri

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: 8),
            child: IconButton(
              onPressed: () {
                Navigator.push(
                  context,
                  MaterialPageRoute(builder: (context) => const CartScreen()),
                );
              },
              icon: 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'),
          ),
        ],
      ),
    );
  }
}

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

  @override
  Widget build(BuildContext context) {
    final cart = context.watch<CartModel>();
    return Scaffold(
      appBar: AppBar(title: const Text('Your Cart')),
      body: ListView(
        children: [
          for (Product product in cart.items)
            ListTile(
              leading: CircleAvatar(
                backgroundColor: product.color.shade50,
                child: Icon(product.icon, color: product.color),
              ),
              title: Text(product.name),
              trailing: Text(money.format(product.price)),
            ),
        ],
      ),
    );
  }
}