Flutter Templates
Erstellung einer E-Commerce-App mit Flutter, Back4App und Stripe-Integration über Cloud Code

49min
Einführung
Die Entwicklung einer E-Commerce-App umfasst mehrere Komponenten, darunter Produktlisten, Funktionen des Warenkorbs, sichere Zahlungsabwicklung, Bestellverfolgung und Benutzerbewertungen. Die Kombination von Flutters leistungsstarkem UI-Toolkit mit den skalierbaren Backend-Diensten von Back4App vereinfacht den Entwicklungsprozess. Darüber hinaus ermöglicht die Integration von Stripe für die Zahlungsabwicklung über Back4App Cloud Code eine sichere und professionelle Transaktionsabwicklung.
In diesem Tutorial werden Sie eine E-Commerce-App mit den folgenden Funktionen erstellen:
Produktlisten: Produkte mit Bildern, Beschreibungen und Preisen anzeigen.
Warenkorb: Produkte zum Warenkorb hinzufügen und entfernen.
Benutzerkonten: Benutzerprofile und Adressen verwalten.
Sicherer Checkout: Zahlungen sicher über Stripe via Back4App Cloud Code abwickeln.
Bestellverfolgung: Bestellstatus und -verlauf verfolgen.
Bewertungen und Bewertungen: Benutzern ermöglichen, Bewertungen und Bewertungen abzugeben.
Voraussetzungen
Um dieses Tutorial zu befolgen, benötigen Sie:
Flutter SDK auf Ihrem Computer installiert. Folgen Sie dem Flutter-Installationshandbuch.
Grundkenntnisse in Flutter und Dart.
Eine IDE oder einen Texteditor wie Visual Studio Code oder Android Studio.
Ein Back4App-Konto. Melden Sie sich bei Back4App an.
Stripe-Konto. Melden Sie sich bei Stripe an, um API-Schlüssel zu erhalten.
Node.js und npm installiert für die Entwicklung von Cloud-Code.
﻿
Schritt 1 – Einrichten des Flutter-Projekts
1.1. Erstellen Sie ein neues Flutter-Projekt
Öffnen Sie Ihr Terminal und führen Sie aus:
Bash
flutter create ecommerce_app
flutter create ecommerce_app
﻿
Navigieren Sie zum Projektverzeichnis:
Bash
cd ecommerce_app
cd ecommerce_app
﻿
1.2. Abhängigkeiten hinzufügen
Öffnen Sie pubspec.yaml und fügen Sie die folgenden Abhängigkeiten hinzu:
YAML
dependencies:
  flutter:
    sdk: flutter
  parse_server_sdk_flutter: ^4.0.1
  provider: ^6.0.0
  cached_network_image: ^3.2.0
  flutter_stripe: ^5.2.0
  uuid: ^3.0.6
dependencies:
  flutter:
    sdk: flutter
  parse_server_sdk_flutter: ^4.0.1
  provider: ^6.0.0
  cached_network_image: ^3.2.0
  flutter_stripe: ^5.2.0
  uuid: ^3.0.6
﻿
Führen Sie flutter pub get aus, um die Pakete zu installieren.
Hinweis:
parse_server_sdk_flutter für die Back4App-Integration.
provider für das State Management.
cached_network_image für effizientes Laden von Bildern.
flutter_stripe für die Stripe-Integration auf der Client-Seite.
uuid zur Generierung eindeutiger Identifikatoren.
  
Schritt 2 – Back4App einrichten
2.1. Erstellen Sie eine neue Back4App-Anwendung
Melden Sie sich bei Ihrem Back4App-Dashboard an.
Klicken Sie auf "Neue App erstellen".
Geben Sie "EcommerceApp" als Anwendungsnamen ein und klicken Sie auf "Erstellen".
2.2. Einrichten der Datenmodelle
Wir müssen mehrere Klassen in Back4App erstellen:
Produkt
Benutzer (Integrierte Klasse)
Bestellung
Bestellposition
Bewertung
2.2.1. Produktklasse
Navigieren Sie zu der "Datenbank"-Sektion.
Klicken Sie auf "Eine Klasse erstellen".
Wählen Sie "Benutzerdefiniert" und geben Sie "Produkt" als Klassennamen ein.
Fügen Sie die folgenden Spalten hinzu:
name: String
beschreibung: String
preis: Zahl
bild: Datei
kategorie: String
lagerbestand: Zahl
2.2.2. Bestellklasse
Erstellen Sie eine "Bestellung" Klasse mit den folgenden Spalten:
benutzer: Pointer<_User>
gesamtbetrag: Zahl
status: String (Werte: "ausstehend", "bezahlt", "versendet", "zugestellt")
paymentIntentId: String (Um Stripe-Zahlung zu verfolgen)
versandadresse: String
2.2.3. Bestellposition Klasse
Erstellen Sie eine "OrderItem"-Klasse mit den folgenden Spalten:
Bestellung: Zeiger
Produkt: Zeiger
Menge: Zahl
Preis: Zahl
2.2.4. Bewertungs-Klasse
Erstellen Sie eine "Review"-Klasse mit den folgenden Spalten:
Produkt: Zeiger
Benutzer: Zeiger<_User>
Bewertung: Zahl
Kommentar: String
2.3. Anwendungsanmeldeinformationen erhalten
Navigieren Sie zu App-Einstellungen > Sicherheit & Schlüssel.
Notieren Sie sich Ihre Anwendungs-ID und Client-Schlüssel.
  
Schritt 3 – Implementierung des Produktmanagements
3.1. Initialisierung von Parse in Flutter
Öffnen Sie lib/main.dart und ändern Sie es:
Dart
import 'package:flutter/material.dart';
import 'package:parse_server_sdk_flutter/parse_server_sdk.dart';
import 'package:provider/provider.dart';
import 'screens/home_screen.dart';
import 'services/product_service.dart';

void main() async {
  WidgetsFlutterBinding.ensureInitialized();

  const keyApplicationId = 'YOUR_APPLICATION_ID';
  const keyClientKey = 'YOUR_CLIENT_KEY';
  const keyParseServerUrl = 'https://parseapi.back4app.com';

  await Parse().initialize(
    keyApplicationId,
    keyParseServerUrl,
    clientKey: keyClientKey,
    autoSendSessionId: true,
    debug: true,
  );

  runApp(MyApp());
}

class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return ChangeNotifierProvider<ProductService>(
      create: (_) => ProductService(),
      child: MaterialApp(
        title: 'E-commerce App',
        theme: ThemeData(
          primarySwatch: Colors.blue,
        ),
        home: HomeScreen(),
      ),
    );
  }
}
import 'package:flutter/material.dart';
import 'package:parse_server_sdk_flutter/parse_server_sdk.dart';
import 'package:provider/provider.dart';
import 'screens/home_screen.dart';
import 'services/product_service.dart';

void main() async {
  WidgetsFlutterBinding.ensureInitialized();

  const keyApplicationId = 'YOUR_APPLICATION_ID';
  const keyClientKey = 'YOUR_CLIENT_KEY';
  const keyParseServerUrl = 'https://parseapi.back4app.com';

  await Parse().initialize(
    keyApplicationId,
    keyParseServerUrl,
    clientKey: keyClientKey,
    autoSendSessionId: true,
    debug: true,
  );

  runApp(MyApp());
}

class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return ChangeNotifierProvider<ProductService>(
      create: (_) => ProductService(),
      child: MaterialApp(
        title: 'E-commerce App',
        theme: ThemeData(
          primarySwatch: Colors.blue,
        ),
        home: HomeScreen(),
      ),
    );
  }
}
﻿
Ersetzen Sie 'YOUR_APPLICATION_ID' und 'YOUR_CLIENT_KEY' durch Ihre Back4App-Anmeldeinformationen.
3.2. Erstellen des Produktmodells
Erstellen Sie ein Verzeichnis models unter lib und fügen Sie product.dart:
Dart
// lib/models/product.dart
class Product {
  String id;
  String name;
  String description;
  double price;
  String imageUrl;
  String category;
  int inventory;

  Product({
    required this.id,
    required this.name,
    required this.description,
    required this.price,
    required this.imageUrl,
    required this.category,
    required this.inventory,
  });
}
// lib/models/product.dart
class Product {
  String id;
  String name;
  String description;
  double price;
  String imageUrl;
  String category;
  int inventory;

  Product({
    required this.id,
    required this.name,
    required this.description,
    required this.price,
    required this.imageUrl,
    required this.category,
    required this.inventory,
  });
}
﻿
3.3. Implementierung des Produktdienstes
Erstellen Sie ein Verzeichnis services unter lib und fügen Sie product_service.dart:
Dart
// lib/services/product_service.dart
import 'package:flutter/material.dart';
import 'package:parse_server_sdk_flutter/parse_server_sdk.dart';
import '../models/product.dart';

class ProductService with ChangeNotifier {
  List<Product> products = [];

  Future<void> fetchProducts() async {
    final query = QueryBuilder<ParseObject>(ParseObject('Product'));

    final response = await query.query();

    if (response.success && response.results != null) {
      products = response.results!.map((data) {
        return Product(
          id: data.objectId!,
          name: data.get<String>('name')!,
          description: data.get<String>('description')!,
          price: data.get<num>('price')!.toDouble(),
          imageUrl: data.get<ParseFileBase>('image')!.url!,
          category: data.get<String>('category')!,
          inventory: data.get<num>('inventory')!.toInt(),
        );
      }).toList();

      notifyListeners();
    }
  }
}
// lib/services/product_service.dart
import 'package:flutter/material.dart';
import 'package:parse_server_sdk_flutter/parse_server_sdk.dart';
import '../models/product.dart';

class ProductService with ChangeNotifier {
  List<Product> products = [];

  Future<void> fetchProducts() async {
    final query = QueryBuilder<ParseObject>(ParseObject('Product'));

    final response = await query.query();

    if (response.success && response.results != null) {
      products = response.results!.map((data) {
        return Product(
          id: data.objectId!,
          name: data.get<String>('name')!,
          description: data.get<String>('description')!,
          price: data.get<num>('price')!.toDouble(),
          imageUrl: data.get<ParseFileBase>('image')!.url!,
          category: data.get<String>('category')!,
          inventory: data.get<num>('inventory')!.toInt(),
        );
      }).toList();

      notifyListeners();
    }
  }
}
﻿
3.4. Erstellen des Startbildschirms
Erstellen Sie screens Verzeichnis unter lib und fügen Sie home_screen.dart:
Dart
// lib/screens/home_screen.dart
import 'package:flutter/material.dart';
import 'package:provider/provider.dart';
import '../services/product_service.dart';
import 'product_detail_screen.dart';

class HomeScreen extends StatefulWidget {
  @override
  _HomeScreenState createState() => _HomeScreenState();
}

class _HomeScreenState extends State<HomeScreen> {
  late ProductService _productService;

  @override
  void initState() {
    super.initState();
    _productService = Provider.of<ProductService>(context, listen: false);
    _productService.fetchProducts();
  }

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: Text('E-commerce App'),
        actions: [
          IconButton(
            icon: Icon(Icons.shopping_cart),
            onPressed: () {
              // Navigate to cart screen (to be implemented)
            },
          ),
        ],
      ),
      body: Consumer<ProductService>(
        builder: (context, productService, child) {
          if (productService.products.isEmpty) {
            return Center(child: CircularProgressIndicator());
          }

          return GridView.builder(
            padding: EdgeInsets.all(8.0),
            itemCount: productService.products.length,
            gridDelegate: SliverGridDelegateWithFixedCrossAxisCount(
              crossAxisCount: 2,
              childAspectRatio: 0.75,
            ),
            itemBuilder: (context, index) {
              final product = productService.products[index];
              return GestureDetector(
                onTap: () {
                  Navigator.push(
                    context,
                    MaterialPageRoute(
                      builder: (_) => ProductDetailScreen(product: product),
                    ),
                  );
                },
                child: Card(
                  child: Column(
                    children: [
                      Expanded(
                        child: Image.network(
                          product.imageUrl,
                          fit: BoxFit.cover,
                        ),
                      ),
                      Text(product.name),
                      Text('\$${product.price.toStringAsFixed(2)}'),
                    ],
                  ),
                ),
              );
            },
          );
        },
      ),
    );
  }
}
// lib/screens/home_screen.dart
import 'package:flutter/material.dart';
import 'package:provider/provider.dart';
import '../services/product_service.dart';
import 'product_detail_screen.dart';

class HomeScreen extends StatefulWidget {
  @override
  _HomeScreenState createState() => _HomeScreenState();
}

class _HomeScreenState extends State<HomeScreen> {
  late ProductService _productService;

  @override
  void initState() {
    super.initState();
    _productService = Provider.of<ProductService>(context, listen: false);
    _productService.fetchProducts();
  }

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: Text('E-commerce App'),
        actions: [
          IconButton(
            icon: Icon(Icons.shopping_cart),
            onPressed: () {
              // Navigate to cart screen (to be implemented)
            },
          ),
        ],
      ),
      body: Consumer<ProductService>(
        builder: (context, productService, child) {
          if (productService.products.isEmpty) {
            return Center(child: CircularProgressIndicator());
          }

          return GridView.builder(
            padding: EdgeInsets.all(8.0),
            itemCount: productService.products.length,
            gridDelegate: SliverGridDelegateWithFixedCrossAxisCount(
              crossAxisCount: 2,
              childAspectRatio: 0.75,
            ),
            itemBuilder: (context, index) {
              final product = productService.products[index];
              return GestureDetector(
                onTap: () {
                  Navigator.push(
                    context,
                    MaterialPageRoute(
                      builder: (_) => ProductDetailScreen(product: product),
                    ),
                  );
                },
                child: Card(
                  child: Column(
                    children: [
                      Expanded(
                        child: Image.network(
                          product.imageUrl,
                          fit: BoxFit.cover,
                        ),
                      ),
                      Text(product.name),
                      Text('\$${product.price.toStringAsFixed(2)}'),
                    ],
                  ),
                ),
              );
            },
          );
        },
      ),
    );
  }
}
﻿
3.5. Produktdetailbildschirm
Erstellen Sie product_detail_screen.dart unter lib/screens/:
Dart
// lib/screens/product_detail_screen.dart
import 'package:flutter/material.dart';
import '../models/product.dart';
import '../services/cart_service.dart';
import 'package:provider/provider.dart';

class ProductDetailScreen extends StatelessWidget {
  final Product product;

  ProductDetailScreen({required this.product});

  @override
  Widget build(BuildContext context) {
    final cartService = Provider.of<CartService>(context);

    return Scaffold(
      appBar: AppBar(title: Text(product.name)),
      body: Column(
        children: [
          Expanded(child: Image.network(product.imageUrl)),
          Padding(
            padding: const EdgeInsets.all(16.0),
            child: Text(product.description),
          ),
          Text('\$${product.price.toStringAsFixed(2)}'),
          ElevatedButton(
            onPressed: () {
              cartService.addToCart(product);
              ScaffoldMessenger.of(context).showSnackBar(
                SnackBar(content: Text('Added to cart')),
              );
            },
            child: Text('Add to Cart'),
          ),
        ],
      ),
    );
  }
}
// lib/screens/product_detail_screen.dart
import 'package:flutter/material.dart';
import '../models/product.dart';
import '../services/cart_service.dart';
import 'package:provider/provider.dart';

class ProductDetailScreen extends StatelessWidget {
  final Product product;

  ProductDetailScreen({required this.product});

  @override
  Widget build(BuildContext context) {
    final cartService = Provider.of<CartService>(context);

    return Scaffold(
      appBar: AppBar(title: Text(product.name)),
      body: Column(
        children: [
          Expanded(child: Image.network(product.imageUrl)),
          Padding(
            padding: const EdgeInsets.all(16.0),
            child: Text(product.description),
          ),
          Text('\$${product.price.toStringAsFixed(2)}'),
          ElevatedButton(
            onPressed: () {
              cartService.addToCart(product);
              ScaffoldMessenger.of(context).showSnackBar(
                SnackBar(content: Text('Added to cart')),
              );
            },
            child: Text('Add to Cart'),
          ),
        ],
      ),
    );
  }
}
﻿
  
Schritt 4 – Implementierung von Benutzerkonten
4.1. Authentifizierungsdienst
Fügen Sie auth_service.dart unter lib/services/:
Dart
// lib/services/auth_service.dart
import 'package:flutter/material.dart';
import 'package:parse_server_sdk_flutter/parse_server_sdk.dart';

class AuthService with ChangeNotifier {
  ParseUser? user;

  Future<bool> signUp(String username, String password, String email) async {
    user = ParseUser.createUser(username, password, email);
    final response = await user!.signUp();

    if (response.success) {
      notifyListeners();
      return true;
    } else {
      user = null;
      return false;
    }
  }

  Future<bool> login(String username, String password) async {
    user = ParseUser(username, password, null);
    final response = await user!.login();

    if (response.success) {
      notifyListeners();
      return true;
    } else {
      user = null;
      return false;
    }
  }

  Future<void> logout() async {
    if (user != null) {
      await user!.logout();
      user = null;
      notifyListeners();
    }
  }

  bool get isAuthenticated => user != null;
}
// lib/services/auth_service.dart
import 'package:flutter/material.dart';
import 'package:parse_server_sdk_flutter/parse_server_sdk.dart';

class AuthService with ChangeNotifier {
  ParseUser? user;

  Future<bool> signUp(String username, String password, String email) async {
    user = ParseUser.createUser(username, password, email);
    final response = await user!.signUp();

    if (response.success) {
      notifyListeners();
      return true;
    } else {
      user = null;
      return false;
    }
  }

  Future<bool> login(String username, String password) async {
    user = ParseUser(username, password, null);
    final response = await user!.login();

    if (response.success) {
      notifyListeners();
      return true;
    } else {
      user = null;
      return false;
    }
  }

  Future<void> logout() async {
    if (user != null) {
      await user!.logout();
      user = null;
      notifyListeners();
    }
  }

  bool get isAuthenticated => user != null;
}
﻿
4.2. Authentifizierungsbildschirme
Erstellen Sie login_screen.dart und signup_screen.dart unter lib/screens/.
Anmeldeseite:
Dart
// lib/screens/login_screen.dart
import 'package:flutter/material.dart';
import 'package:provider/provider.dart';
import '../services/auth_service.dart';
import 'home_screen.dart';
import 'signup_screen.dart';

class LoginScreen extends StatelessWidget {
  final TextEditingController _usernameController = TextEditingController();
  final TextEditingController _passwordController = TextEditingController();

  void _login(BuildContext context) async {
    final authService = Provider.of<AuthService>(context, listen: false);
    bool success = await authService.login(
      _usernameController.text.trim(),
      _passwordController.text.trim(),
    );

    if (success) {
      Navigator.pushReplacement(
        context,
        MaterialPageRoute(builder: (_) => HomeScreen()),
      );
    } else {
      ScaffoldMessenger.of(context)
          .showSnackBar(SnackBar(content: Text('Login failed')));
    }
  }

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: Text('E-commerce App Login'),
      ),
      body: Padding(
        padding: const EdgeInsets.all(16),
        child: Column(
          children: [
            TextField(
              controller: _usernameController,
              decoration: InputDecoration(labelText: 'Username or Email'),
            ),
            TextField(
              controller: _passwordController,
              decoration: InputDecoration(labelText: 'Password'),
              obscureText: true,
            ),
            SizedBox(height: 20),
            ElevatedButton(
              onPressed: () => _login(context),
              child: Text('Login'),
            ),
            TextButton(
              onPressed: () {
                Navigator.push(
                  context,
                  MaterialPageRoute(builder: (_) => SignupScreen()),
                );
              },
              child: Text('Don\'t have an account? Sign up'),
            )
          ],
        ),
      ),
    );
  }
}
// lib/screens/login_screen.dart
import 'package:flutter/material.dart';
import 'package:provider/provider.dart';
import '../services/auth_service.dart';
import 'home_screen.dart';
import 'signup_screen.dart';

class LoginScreen extends StatelessWidget {
  final TextEditingController _usernameController = TextEditingController();
  final TextEditingController _passwordController = TextEditingController();

  void _login(BuildContext context) async {
    final authService = Provider.of<AuthService>(context, listen: false);
    bool success = await authService.login(
      _usernameController.text.trim(),
      _passwordController.text.trim(),
    );

    if (success) {
      Navigator.pushReplacement(
        context,
        MaterialPageRoute(builder: (_) => HomeScreen()),
      );
    } else {
      ScaffoldMessenger.of(context)
          .showSnackBar(SnackBar(content: Text('Login failed')));
    }
  }

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: Text('E-commerce App Login'),
      ),
      body: Padding(
        padding: const EdgeInsets.all(16),
        child: Column(
          children: [
            TextField(
              controller: _usernameController,
              decoration: InputDecoration(labelText: 'Username or Email'),
            ),
            TextField(
              controller: _passwordController,
              decoration: InputDecoration(labelText: 'Password'),
              obscureText: true,
            ),
            SizedBox(height: 20),
            ElevatedButton(
              onPressed: () => _login(context),
              child: Text('Login'),
            ),
            TextButton(
              onPressed: () {
                Navigator.push(
                  context,
                  MaterialPageRoute(builder: (_) => SignupScreen()),
                );
              },
              child: Text('Don\'t have an account? Sign up'),
            )
          ],
        ),
      ),
    );
  }
}
﻿
Registrierungsseite:
Dart
// lib/screens/signup_screen.dart
import 'package:flutter/material.dart';
import 'package:provider/provider.dart';
import '../services/auth_service.dart';
import 'home_screen.dart';

class SignupScreen extends StatelessWidget {
  final TextEditingController _usernameController = TextEditingController();
  final TextEditingController _emailController = TextEditingController();
  final TextEditingController _passwordController = TextEditingController();

  void _signUp(BuildContext context) async {
    final authService = Provider.of<AuthService>(context, listen: false);
    bool success = await authService.signUp(
      _usernameController.text.trim(),
      _passwordController.text.trim(),
      _emailController.text.trim(),
    );

    if (success) {
      Navigator.pushReplacement(
        context,
        MaterialPageRoute(builder: (_) => HomeScreen()),
      );
    } else {
      ScaffoldMessenger.of(context)
          .showSnackBar(SnackBar(content: Text('Signup failed')));
    }
  }

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: Text('E-commerce App Signup'),
      ),
      body: Padding(
        padding: const EdgeInsets.all(16),
        child: Column(
          children: [
            TextField(
              controller: _usernameController,
              decoration: InputDecoration(labelText: 'Username'),
            ),
            TextField(
              controller: _emailController,
              decoration: InputDecoration(labelText: 'Email'),
            ),
            TextField(
              controller: _passwordController,
              decoration: InputDecoration(labelText: 'Password'),
              obscureText: true,
            ),
            SizedBox(height: 20),
            ElevatedButton(
              onPressed: () => _signUp(context),
              child: Text('Sign Up'),
            ),
          ],
        ),
      ),
    );
  }
}
// lib/screens/signup_screen.dart
import 'package:flutter/material.dart';
import 'package:provider/provider.dart';
import '../services/auth_service.dart';
import 'home_screen.dart';

class SignupScreen extends StatelessWidget {
  final TextEditingController _usernameController = TextEditingController();
  final TextEditingController _emailController = TextEditingController();
  final TextEditingController _passwordController = TextEditingController();

  void _signUp(BuildContext context) async {
    final authService = Provider.of<AuthService>(context, listen: false);
    bool success = await authService.signUp(
      _usernameController.text.trim(),
      _passwordController.text.trim(),
      _emailController.text.trim(),
    );

    if (success) {
      Navigator.pushReplacement(
        context,
        MaterialPageRoute(builder: (_) => HomeScreen()),
      );
    } else {
      ScaffoldMessenger.of(context)
          .showSnackBar(SnackBar(content: Text('Signup failed')));
    }
  }

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: Text('E-commerce App Signup'),
      ),
      body: Padding(
        padding: const EdgeInsets.all(16),
        child: Column(
          children: [
            TextField(
              controller: _usernameController,
              decoration: InputDecoration(labelText: 'Username'),
            ),
            TextField(
              controller: _emailController,
              decoration: InputDecoration(labelText: 'Email'),
            ),
            TextField(
              controller: _passwordController,
              decoration: InputDecoration(labelText: 'Password'),
              obscureText: true,
            ),
            SizedBox(height: 20),
            ElevatedButton(
              onPressed: () => _signUp(context),
              child: Text('Sign Up'),
            ),
          ],
        ),
      ),
    );
  }
}
﻿
4.3. Hauptaktualisierung zur Einbeziehung von AuthService
In main.dart, um die MaterialApp mit MultiProvider:
Dart
// In main.dart
class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return MultiProvider(
      providers: [
        ChangeNotifierProvider<ProductService>(
          create: (_) => ProductService(),
        ),
        ChangeNotifierProvider<AuthService>(
          create: (_) => AuthService(),
        ),
        ChangeNotifierProvider<CartService>(
          create: (_) => CartService(),
        ),
      ],
      child: MaterialApp(
        // ...
      ),
    );
  }
}
// In main.dart
class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return MultiProvider(
      providers: [
        ChangeNotifierProvider<ProductService>(
          create: (_) => ProductService(),
        ),
        ChangeNotifierProvider<AuthService>(
          create: (_) => AuthService(),
        ),
        ChangeNotifierProvider<CartService>(
          create: (_) => CartService(),
        ),
      ],
      child: MaterialApp(
        // ...
      ),
    );
  }
}
﻿
4.4. Weiterleitung basierend auf dem Authentifizierungsstatus
Ändern Sie main.dart um den Authentifizierungsstatus zu überprüfen:
Dart
// main.dart
// Inside the build method
home: Consumer<AuthService>(
  builder: (context, authService, child) {
    if (authService.isAuthenticated) {
      return HomeScreen();
    } else {
      return LoginScreen();
    }
  },
),
// main.dart
// Inside the build method
home: Consumer<AuthService>(
  builder: (context, authService, child) {
    if (authService.isAuthenticated) {
      return HomeScreen();
    } else {
      return LoginScreen();
    }
  },
),
﻿
  
Schritt 5 – Einkaufswagen-Funktionalität
5.1. Erstelle den Warenkorb-Service
Fügen Sie cart_service.dart unter lib/services/:
Dart
// lib/services/cart_service.dart
import 'package:flutter/material.dart';
import '../models/product.dart';

class CartItem {
  final Product product;
  int quantity;

  CartItem({required this.product, this.quantity = 1});
}

class CartService with ChangeNotifier {
  Map<String, CartItem> _items = {};

  void addToCart(Product product) {
    if (_items.containsKey(product.id)) {
      _items[product.id]!.quantity++;
    } else {
      _items[product.id] = CartItem(product: product);
    }
    notifyListeners();
  }

  void removeFromCart(String productId) {
    _items.remove(productId);
    notifyListeners();
  }

  void clearCart() {
    _items.clear();
    notifyListeners();
  }

  Map<String, CartItem> get items => _items;

  double get totalAmount {
    double total = 0.0;
    _items.forEach((key, cartItem) {
      total += cartItem.product.price * cartItem.quantity;
    });
    return total;
  }
}
// lib/services/cart_service.dart
import 'package:flutter/material.dart';
import '../models/product.dart';

class CartItem {
  final Product product;
  int quantity;

  CartItem({required this.product, this.quantity = 1});
}

class CartService with ChangeNotifier {
  Map<String, CartItem> _items = {};

  void addToCart(Product product) {
    if (_items.containsKey(product.id)) {
      _items[product.id]!.quantity++;
    } else {
      _items[product.id] = CartItem(product: product);
    }
    notifyListeners();
  }

  void removeFromCart(String productId) {
    _items.remove(productId);
    notifyListeners();
  }

  void clearCart() {
    _items.clear();
    notifyListeners();
  }

  Map<String, CartItem> get items => _items;

  double get totalAmount {
    double total = 0.0;
    _items.forEach((key, cartItem) {
      total += cartItem.product.price * cartItem.quantity;
    });
    return total;
  }
}
﻿
5.2. Erstellen Sie den Warenkorb-Bildschirm
Fügen Sie cart_screen.dart unter lib/screens/:
Dart
// lib/screens/cart_screen.dart
import 'package:flutter/material.dart';
import 'package:provider/provider.dart';
import '../services/cart_service.dart';
import 'checkout_screen.dart';

class CartScreen extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    final cartService = Provider.of<CartService>(context);
    final cartItems = cartService.items.values.toList();

    return Scaffold(
      appBar: AppBar(title: Text('Your Cart')),
      body: Column(
        children: [
          Expanded(
            child: ListView.builder(
              itemCount: cartService.items.length,
              itemBuilder: (context, index) {
                final cartItem = cartItems[index];
                return ListTile(
                  leading: Image.network(cartItem.product.imageUrl),
                  title: Text(cartItem.product.name),
                  subtitle: Text('Quantity: ${cartItem.quantity}'),
                  trailing: Text('\$${(cartItem.product.price * cartItem.quantity).toStringAsFixed(2)}'),
                );
              },
            ),
          ),
          Text('Total: \$${cartService.totalAmount.toStringAsFixed(2)}'),
          ElevatedButton(
            onPressed: () {
              Navigator.push(
                context,
                MaterialPageRoute(builder: (_) => CheckoutScreen()),
              );
            },
            child: Text('Proceed to Checkout'),
          ),
        ],
      ),
    );
  }
}
// lib/screens/cart_screen.dart
import 'package:flutter/material.dart';
import 'package:provider/provider.dart';
import '../services/cart_service.dart';
import 'checkout_screen.dart';

class CartScreen extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    final cartService = Provider.of<CartService>(context);
    final cartItems = cartService.items.values.toList();

    return Scaffold(
      appBar: AppBar(title: Text('Your Cart')),
      body: Column(
        children: [
          Expanded(
            child: ListView.builder(
              itemCount: cartService.items.length,
              itemBuilder: (context, index) {
                final cartItem = cartItems[index];
                return ListTile(
                  leading: Image.network(cartItem.product.imageUrl),
                  title: Text(cartItem.product.name),
                  subtitle: Text('Quantity: ${cartItem.quantity}'),
                  trailing: Text('\$${(cartItem.product.price * cartItem.quantity).toStringAsFixed(2)}'),
                );
              },
            ),
          ),
          Text('Total: \$${cartService.totalAmount.toStringAsFixed(2)}'),
          ElevatedButton(
            onPressed: () {
              Navigator.push(
                context,
                MaterialPageRoute(builder: (_) => CheckoutScreen()),
              );
            },
            child: Text('Proceed to Checkout'),
          ),
        ],
      ),
    );
  }
}
﻿
  
Schritt 6 – Sicherer Checkout mit Stripe-Integration über Cloud Code
6.1. Stripe-Konto einrichten
Melden Sie sich für ein Stripe-Konto an.
Holen Sie sich Ihren Publishable Key und Secret Key im Stripe-Dashboard unter Entwickler > API-Schlüssel.
6.2. Stripe SDK im Cloud Code installieren
Back4App unterstützt Cloud Code-Funktionen, die in JavaScript geschrieben sind. Wir werden Cloud Code-Funktionen schreiben, um die Zahlungsabwicklung zu verwalten.
6.2.1. Cloud Code-Projekt erstellen
Gehen Sie in Ihrem Back4App-App-Dashboard zu App-Einstellungen > Cloud Code-Funktionen.
Klicken Sie auf "Code bearbeiten" um den Cloud Code-Editor zu öffnen.
6.2.2. npm initialisieren und Stripe-Paket installieren
Führen Sie im Cloud Code-Terminal (im Editor bereitgestellt) aus:
Bash
npm init -y
npm install [email protected]
npm init -y
npm install stripe@8.174.0
﻿
Hinweis: Back4App's Cloud Code verwendet Node.js Version 14.x, stellen Sie also die Kompatibilität sicher.
6.3. Erstellen Sie eine Cloud-Funktion für die Zahlungsabsicht
Erstellen oder ändern Sie main.js im Cloud Code-Editor:
JS
// main.js
const Stripe = require('stripe');
const stripe = Stripe('YOUR_STRIPE_SECRET_KEY');

Parse.Cloud.define('createPaymentIntent', async (request) => {
  const { amount, currency } = request.params;

  try {
    const paymentIntent = await stripe.paymentIntents.create({
      amount: amount,
      currency: currency,
    });

    return { clientSecret: paymentIntent.client_secret };
  } catch (error) {
    throw new Parse.Error(500, error.message);
  }
});
// main.js
const Stripe = require('stripe');
const stripe = Stripe('YOUR_STRIPE_SECRET_KEY');

Parse.Cloud.define('createPaymentIntent', async (request) => {
  const { amount, currency } = request.params;

  try {
    const paymentIntent = await stripe.paymentIntents.create({
      amount: amount,
      currency: currency,
    });

    return { clientSecret: paymentIntent.client_secret };
  } catch (error) {
    throw new Parse.Error(500, error.message);
  }
});
﻿
Ersetzen Sie 'YOUR_STRIPE_SECRET_KEY' durch Ihren tatsächlichen Stripe-Geheimschlüssel.
Sicherheitsnotiz: Geben Sie Ihren geheimen Schlüssel niemals auf der Client-Seite preis. Halten Sie ihn im Cloud Code sicher.
6.4. Cloud Code bereitstellen
Klicken Sie auf "Bereitstellen" im Cloud Code-Editor, um Ihre Funktionen bereitzustellen.
6.5. Implementierung der Zahlung in Flutter
6.5.1. Stripe in Flutter initialisieren
In main.dart, nach Parse().initialize, hinzufügen:
Dart
import 'package:flutter_stripe/flutter_stripe.dart';

// Inside main() async
Stripe.publishableKey = 'YOUR_STRIPE_PUBLISHABLE_KEY';
import 'package:flutter_stripe/flutter_stripe.dart';

// Inside main() async
Stripe.publishableKey = 'YOUR_STRIPE_PUBLISHABLE_KEY';
﻿
Ersetzen Sie 'IHRE_STRIPE_PUBLISHABLE_KEY' durch Ihren Stripe-Publishable-Key.
6.5.2. Checkout-Bildschirm erstellen
Fügen Sie checkout_screen.dart unter lib/screens/:
Dart
// lib/screens/checkout_screen.dart
import 'package:flutter/material.dart';
import 'package:provider/provider.dart';
import '../services/cart_service.dart';
import 'package:flutter_stripe/flutter_stripe.dart';
import 'package:parse_server_sdk_flutter/parse_server_sdk.dart';
import 'order_confirmation_screen.dart';

class CheckoutScreen extends StatelessWidget {
  Future<void> _processPayment(BuildContext context) async {
    final cartService = Provider.of<CartService>(context, listen: false);
    final totalAmount = (cartService.totalAmount * 100).toInt(); // Amount in cents

    // Call Cloud Function to create Payment Intent
    final response = await ParseCloudFunction('createPaymentIntent').execute(
      parameters: {
        'amount': totalAmount,
        'currency': 'usd',
      },
    );

    if (response.success) {
      final clientSecret = response.result['clientSecret'];

      // Initialize payment sheet
      await Stripe.instance.initPaymentSheet(
        paymentSheetParameters: SetupPaymentSheetParameters(
          paymentIntentClientSecret: clientSecret,
          merchantDisplayName: 'Your E-commerce App',
        ),
      );

      // Display payment sheet
      await Stripe.instance.presentPaymentSheet();

      // Payment successful
      // Save order to Back4App (to be implemented)
      cartService.clearCart();
      Navigator.pushReplacement(
        context,
        MaterialPageRoute(builder: (_) => OrderConfirmationScreen()),
      );
    } else {
      ScaffoldMessenger.of(context).showSnackBar(
        SnackBar(content: Text('Payment failed: ${response.error!.message}')),
      );
    }
  }

  @override
  Widget build(BuildContext context) {
    final cartService = Provider.of<CartService>(context);

    return Scaffold(
      appBar: AppBar(title: Text('Checkout')),
      body: Column(
        children: [
          Text('Total: \$${cartService.totalAmount.toStringAsFixed(2)}'),
          ElevatedButton(
            onPressed: () => _processPayment(context),
            child: Text('Pay Now'),
          ),
        ],
      ),
    );
  }
}
// lib/screens/checkout_screen.dart
import 'package:flutter/material.dart';
import 'package:provider/provider.dart';
import '../services/cart_service.dart';
import 'package:flutter_stripe/flutter_stripe.dart';
import 'package:parse_server_sdk_flutter/parse_server_sdk.dart';
import 'order_confirmation_screen.dart';

class CheckoutScreen extends StatelessWidget {
  Future<void> _processPayment(BuildContext context) async {
    final cartService = Provider.of<CartService>(context, listen: false);
    final totalAmount = (cartService.totalAmount * 100).toInt(); // Amount in cents

    // Call Cloud Function to create Payment Intent
    final response = await ParseCloudFunction('createPaymentIntent').execute(
      parameters: {
        'amount': totalAmount,
        'currency': 'usd',
      },
    );

    if (response.success) {
      final clientSecret = response.result['clientSecret'];

      // Initialize payment sheet
      await Stripe.instance.initPaymentSheet(
        paymentSheetParameters: SetupPaymentSheetParameters(
          paymentIntentClientSecret: clientSecret,
          merchantDisplayName: 'Your E-commerce App',
        ),
      );

      // Display payment sheet
      await Stripe.instance.presentPaymentSheet();

      // Payment successful
      // Save order to Back4App (to be implemented)
      cartService.clearCart();
      Navigator.pushReplacement(
        context,
        MaterialPageRoute(builder: (_) => OrderConfirmationScreen()),
      );
    } else {
      ScaffoldMessenger.of(context).showSnackBar(
        SnackBar(content: Text('Payment failed: ${response.error!.message}')),
      );
    }
  }

  @override
  Widget build(BuildContext context) {
    final cartService = Provider.of<CartService>(context);

    return Scaffold(
      appBar: AppBar(title: Text('Checkout')),
      body: Column(
        children: [
          Text('Total: \$${cartService.totalAmount.toStringAsFixed(2)}'),
          ElevatedButton(
            onPressed: () => _processPayment(context),
            child: Text('Pay Now'),
          ),
        ],
      ),
    );
  }
}
﻿
6.5.3. Zahlungsbestätigung behandeln
Erstellen Sie order_confirmation_screen.dart unter lib/screens/:
Dart
// lib/screens/order_confirmation_screen.dart
import 'package:flutter/material.dart';

class OrderConfirmationScreen extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: Text('Order Confirmed'),
        automaticallyImplyLeading: false,
      ),
      body: Center(
        child: Text('Thank you for your purchase!'),
      ),
    );
  }
}
// lib/screens/order_confirmation_screen.dart
import 'package:flutter/material.dart';

class OrderConfirmationScreen extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: Text('Order Confirmed'),
        automaticallyImplyLeading: false,
      ),
      body: Center(
        child: Text('Thank you for your purchase!'),
      ),
    );
  }
}
﻿
6.6. Bestellung in Back4App speichern
Ändern Sie die _processPayment Methode, um die Bestelldaten zu speichern:
Dart
// After successful payment
final authService = Provider.of<AuthService>(context, listen: false);
final user = authService.user!;

// Create Order object
final order = ParseObject('Order')
  ..set('user', user)
  ..set('totalAmount', cartService.totalAmount)
  ..set('status', 'paid')
  ..set('paymentIntentId', clientSecret);

// Save Order
final orderResponse = await order.save();

if (orderResponse.success) {
  final orderObject = orderResponse.result;

  // Save OrderItems
  for (var cartItem in cartService.items.values) {
    final orderItem = ParseObject('OrderItem')
      ..set('order', orderObject)
      ..set('product', ParseObject('Product')..objectId = cartItem.product.id)
      ..set('quantity', cartItem.quantity)
      ..set('price', cartItem.product.price);

    await orderItem.save();
  }

  // Clear cart and navigate
  cartService.clearCart();
  Navigator.pushReplacement(
    context,
    MaterialPageRoute(builder: (_) => OrderConfirmationScreen()),
  );
} else {
  ScaffoldMessenger.of(context).showSnackBar(
    SnackBar(content: Text('Failed to save order')),
  );
}
// After successful payment
final authService = Provider.of<AuthService>(context, listen: false);
final user = authService.user!;

// Create Order object
final order = ParseObject('Order')
  ..set('user', user)
  ..set('totalAmount', cartService.totalAmount)
  ..set('status', 'paid')
  ..set('paymentIntentId', clientSecret);

// Save Order
final orderResponse = await order.save();

if (orderResponse.success) {
  final orderObject = orderResponse.result;

  // Save OrderItems
  for (var cartItem in cartService.items.values) {
    final orderItem = ParseObject('OrderItem')
      ..set('order', orderObject)
      ..set('product', ParseObject('Product')..objectId = cartItem.product.id)
      ..set('quantity', cartItem.quantity)
      ..set('price', cartItem.product.price);

    await orderItem.save();
  }

  // Clear cart and navigate
  cartService.clearCart();
  Navigator.pushReplacement(
    context,
    MaterialPageRoute(builder: (_) => OrderConfirmationScreen()),
  );
} else {
  ScaffoldMessenger.of(context).showSnackBar(
    SnackBar(content: Text('Failed to save order')),
  );
}
﻿
  
Schritt 7 – Bestellverfolgung
7.1. Bestellservice erstellen
Fügen Sie order_service.dart unter lib/services/:
Dart
// lib/services/order_service.dart
import 'package:flutter/material.dart';
import 'package:parse_server_sdk_flutter/parse_server_sdk.dart';
import '../models/order.dart';

class OrderService with ChangeNotifier {
  List<Order> orders = [];

  Future<void> fetchOrders(ParseUser user) async {
    final query = QueryBuilder<ParseObject>(ParseObject('Order'))
      ..whereEqualTo('user', user)
      ..orderByDescending('createdAt');

    final response = await query.query();

    if (response.success && response.results != null) {
      orders = response.results!.map((data) {
        return Order.fromParseObject(data);
      }).toList();

      notifyListeners();
    }
  }
}
// lib/services/order_service.dart
import 'package:flutter/material.dart';
import 'package:parse_server_sdk_flutter/parse_server_sdk.dart';
import '../models/order.dart';

class OrderService with ChangeNotifier {
  List<Order> orders = [];

  Future<void> fetchOrders(ParseUser user) async {
    final query = QueryBuilder<ParseObject>(ParseObject('Order'))
      ..whereEqualTo('user', user)
      ..orderByDescending('createdAt');

    final response = await query.query();

    if (response.success && response.results != null) {
      orders = response.results!.map((data) {
        return Order.fromParseObject(data);
      }).toList();

      notifyListeners();
    }
  }
}
﻿
7.2. Bestellmodell erstellen
Fügen Sie order.dart unter lib/models/:
Dart
// lib/models/order.dart
import 'package:parse_server_sdk_flutter/parse_server_sdk.dart';

class Order {
  String id;
  double totalAmount;
  String status;
  DateTime createdAt;

  Order({
    required this.id,
    required this.totalAmount,
    required this.status,
    required this.createdAt,
  });

  factory Order.fromParseObject(ParseObject object) {
    return Order(
      id: object.objectId!,
      totalAmount: object.get<num>('totalAmount')!.toDouble(),
      status: object.get<String>('status')!,
      createdAt: object.createdAt!,
    );
  }
}
// lib/models/order.dart
import 'package:parse_server_sdk_flutter/parse_server_sdk.dart';

class Order {
  String id;
  double totalAmount;
  String status;
  DateTime createdAt;

  Order({
    required this.id,
    required this.totalAmount,
    required this.status,
    required this.createdAt,
  });

  factory Order.fromParseObject(ParseObject object) {
    return Order(
      id: object.objectId!,
      totalAmount: object.get<num>('totalAmount')!.toDouble(),
      status: object.get<String>('status')!,
      createdAt: object.createdAt!,
    );
  }
}
﻿
7.3. Bestellbildschirm erstellen
Fügen Sie orders_screen.dart unter lib/screens/:
Dart
// lib/screens/orders_screen.dart
import 'package:flutter/material.dart';
import 'package:provider/provider.dart';
import '../services/order_service.dart';
import '../services/auth_service.dart';
import '../models/order.dart';

class OrdersScreen extends StatefulWidget {
  @override
  _OrdersScreenState createState() => _OrdersScreenState();
}

class _OrdersScreenState extends State<OrdersScreen> {
  late OrderService _orderService;

  @override
  void initState() {
    super.initState();
    _orderService = Provider.of<OrderService>(context, listen: false);
    final authService = Provider.of<AuthService>(context, listen: false);
    _orderService.fetchOrders(authService.user!);
  }

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(title: Text('Your Orders')),
      body: Consumer<OrderService>(
        builder: (context, orderService, child) {
          if (orderService.orders.isEmpty) {
            return Center(child: Text('No orders found.'));
          }

          return ListView.builder(
            itemCount: orderService.orders.length,
            itemBuilder: (context, index) {
              final order = orderService.orders[index];
              return ListTile(
                title: Text('Order #${order.id}'),
                subtitle: Text('Status: ${order.status}'),
                trailing: Text('\$${order.totalAmount.toStringAsFixed(2)}'),
              );
            },
          );
        },
      ),
    );
  }
}
// lib/screens/orders_screen.dart
import 'package:flutter/material.dart';
import 'package:provider/provider.dart';
import '../services/order_service.dart';
import '../services/auth_service.dart';
import '../models/order.dart';

class OrdersScreen extends StatefulWidget {
  @override
  _OrdersScreenState createState() => _OrdersScreenState();
}

class _OrdersScreenState extends State<OrdersScreen> {
  late OrderService _orderService;

  @override
  void initState() {
    super.initState();
    _orderService = Provider.of<OrderService>(context, listen: false);
    final authService = Provider.of<AuthService>(context, listen: false);
    _orderService.fetchOrders(authService.user!);
  }

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(title: Text('Your Orders')),
      body: Consumer<OrderService>(
        builder: (context, orderService, child) {
          if (orderService.orders.isEmpty) {
            return Center(child: Text('No orders found.'));
          }

          return ListView.builder(
            itemCount: orderService.orders.length,
            itemBuilder: (context, index) {
              final order = orderService.orders[index];
              return ListTile(
                title: Text('Order #${order.id}'),
                subtitle: Text('Status: ${order.status}'),
                trailing: Text('\$${order.totalAmount.toStringAsFixed(2)}'),
              );
            },
          );
        },
      ),
    );
  }
}
﻿
  
Schritt 8 – Bewertungen und Rezensionen
8.1. Bewertungsdienst erstellen
Fügen Sie review_service.dart unter lib/services/:
Dart
// lib/services/review_service.dart
import 'package:flutter/material.dart';
import 'package:parse_server_sdk_flutter/parse_server_sdk.dart';
import '../models/review.dart';

class ReviewService with ChangeNotifier {
  List<Review> reviews = [];

  Future<void> fetchReviews(String productId) async {
    final query = QueryBuilder<ParseObject>(ParseObject('Review'))
      ..whereEqualTo('product', ParseObject('Product')..objectId = productId)
      ..includeObject(['user']);

    final response = await query.query();

    if (response.success && response.results != null) {
      reviews = response.results!.map((data) {
        return Review.fromParseObject(data);
      }).toList();

      notifyListeners();
    }
  }

  Future<void> submitReview(String productId, ParseUser user, int rating, String comment) async {
    final review = ParseObject('Review')
      ..set('product', ParseObject('Product')..objectId = productId)
      ..set('user', user)
      ..set('rating', rating)
      ..set('comment', comment);

    await review.save();
    await fetchReviews(productId);
  }
}
// lib/services/review_service.dart
import 'package:flutter/material.dart';
import 'package:parse_server_sdk_flutter/parse_server_sdk.dart';
import '../models/review.dart';

class ReviewService with ChangeNotifier {
  List<Review> reviews = [];

  Future<void> fetchReviews(String productId) async {
    final query = QueryBuilder<ParseObject>(ParseObject('Review'))
      ..whereEqualTo('product', ParseObject('Product')..objectId = productId)
      ..includeObject(['user']);

    final response = await query.query();

    if (response.success && response.results != null) {
      reviews = response.results!.map((data) {
        return Review.fromParseObject(data);
      }).toList();

      notifyListeners();
    }
  }

  Future<void> submitReview(String productId, ParseUser user, int rating, String comment) async {
    final review = ParseObject('Review')
      ..set('product', ParseObject('Product')..objectId = productId)
      ..set('user', user)
      ..set('rating', rating)
      ..set('comment', comment);

    await review.save();
    await fetchReviews(productId);
  }
}
﻿
8.2. Erstellen Sie das Bewertungsmodell
Fügen Sie review.dart unter lib/models/:
Dart
// lib/models/review.dart
import 'package:parse_server_sdk_flutter/parse_server_sdk.dart';

class Review {
  String id;
  int rating;
  String comment;
  ParseUser user;

  Review({
    required this.id,
    required this.rating,
    required this.comment,
    required this.user,
  });

  factory Review.fromParseObject(ParseObject object) {
    return Review(
      id: object.objectId!,
      rating: object.get<num>('rating')!.toInt(),
      comment: object.get<String>('comment')!,
      user: object.get<ParseUser>('user')!,
    );
  }
}
// lib/models/review.dart
import 'package:parse_server_sdk_flutter/parse_server_sdk.dart';

class Review {
  String id;
  int rating;
  String comment;
  ParseUser user;

  Review({
    required this.id,
    required this.rating,
    required this.comment,
    required this.user,
  });

  factory Review.fromParseObject(ParseObject object) {
    return Review(
      id: object.objectId!,
      rating: object.get<num>('rating')!.toInt(),
      comment: object.get<String>('comment')!,
      user: object.get<ParseUser>('user')!,
    );
  }
}
﻿
8.3. Aktualisieren Sie den Produktdetailbildschirm
In product_detail_screen.dart, fügen Sie einen Abschnitt hinzu, um Bewertungen anzuzeigen und einzureichen.
Dart
// At the end of the Column in ProductDetailScreen
Expanded(
  child: Column(
    children: [
      // Display reviews
      Expanded(
        child: Consumer<ReviewService>(
          builder: (context, reviewService, child) {
            if (reviewService.reviews.isEmpty) {
              return Center(child: Text('No reviews yet.'));
            }

            return ListView.builder(
              itemCount: reviewService.reviews.length,
              itemBuilder: (context, index) {
                final review = reviewService.reviews[index];
                return ListTile(
                  title: Text(review.user.username ?? 'Anonymous'),
                  subtitle: Text(review.comment),
                  trailing: Text('${review.rating}/5'),
                );
              },
            );
          },
        ),
      ),
      // Submit review
      TextField(
        controller: _reviewController,
        decoration: InputDecoration(hintText: 'Write a review'),
      ),
      Row(
        children: [
          Text('Rating:'),
          DropdownButton<int>(
            value: _rating,
            onChanged: (value) {
              setState(() {
                _rating = value!;
              });
            },
            items: List.generate(5, (index) => index + 1)
                .map((e) => DropdownMenuItem(value: e, child: Text('$e')))
                .toList(),
          ),
          ElevatedButton(
            onPressed: () {
              final authService = Provider.of<AuthService>(context, listen: false);
              _reviewService.submitReview(
                product.id,
                authService.user!,
                _rating,
                _reviewController.text.trim(),
              );
              _reviewController.clear();
            },
            child: Text('Submit'),
          ),
        ],
      ),
    ],
  ),
),
// At the end of the Column in ProductDetailScreen
Expanded(
  child: Column(
    children: [
      // Display reviews
      Expanded(
        child: Consumer<ReviewService>(
          builder: (context, reviewService, child) {
            if (reviewService.reviews.isEmpty) {
              return Center(child: Text('No reviews yet.'));
            }

            return ListView.builder(
              itemCount: reviewService.reviews.length,
              itemBuilder: (context, index) {
                final review = reviewService.reviews[index];
                return ListTile(
                  title: Text(review.user.username ?? 'Anonymous'),
                  subtitle: Text(review.comment),
                  trailing: Text('${review.rating}/5'),
                );
              },
            );
          },
        ),
      ),
      // Submit review
      TextField(
        controller: _reviewController,
        decoration: InputDecoration(hintText: 'Write a review'),
      ),
      Row(
        children: [
          Text('Rating:'),
          DropdownButton<int>(
            value: _rating,
            onChanged: (value) {
              setState(() {
                _rating = value!;
              });
            },
            items: List.generate(5, (index) => index + 1)
                .map((e) => DropdownMenuItem(value: e, child: Text('$e')))
                .toList(),
          ),
          ElevatedButton(
            onPressed: () {
              final authService = Provider.of<AuthService>(context, listen: false);
              _reviewService.submitReview(
                product.id,
                authService.user!,
                _rating,
                _reviewController.text.trim(),
              );
              _reviewController.clear();
            },
            child: Text('Submit'),
          ),
        ],
      ),
    ],
  ),
),
﻿
  
Fazit
In diesem umfassenden Tutorial haben Sie eine E-Commerce-App mit Flutter und Back4App erstellt, die mit Stripe für die sichere Zahlungsabwicklung über Cloud Code integriert ist. Sie haben wichtige Funktionen wie Produktlisten, Einkaufswagenfunktionalität, Benutzerauthentifizierung, Bestellverfolgung und Bewertungen implementiert.
Wichtige Erkenntnisse
Back4App-Integration: Vereinfacht das Backend-Management für Ihre Flutter-App.
Stripe-Integration über Cloud Code: Verarbeitet Zahlungen sicher, ohne sensible Schlüssel offenzulegen.
Modulare Architektur: Die Trennung von Diensten und Modellen verbessert die Wartbarkeit.
Nächste Schritte
Sicherheit verbessern: Implementieren Sie eine ordnungsgemäße Fehlerbehandlung und Eingangsvalidierung.
UI/UX Verbesserungen: Verfeinern Sie die Benutzeroberfläche für ein besseres Benutzererlebnis.
Bestandsverwaltung: Aktualisieren Sie den Produktbestand nach dem Kauf.
E-Mail-Benachrichtigungen: Senden Sie Bestellbestätigungs-E-Mails an die Benutzer.
Admin-Panel: Erstellen Sie eine Admin-Oberfläche zur Verwaltung von Produkten und Bestellungen.
Zusätzliche Ressourcen
﻿Back4App Dokumentation﻿
﻿Parse Server Anleitung﻿
﻿Flutter Offizielle Dokumentation﻿
﻿Stripe API Referenz﻿
﻿Flutter Stripe Paket﻿
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Aktualisiert 23 Jan 2025
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