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A new Flutter project.

Getting Started

This project is a starting point for a Flutter application.

A few resources to get you started if this is your first Flutter project:

• Lab: Write your first Flutter app
• Cookbook: Useful Flutter samples

For help getting started with Flutter development, view the online documentation, which offers tutorials, samples, guidance on mobile development, and a full API reference.

Flutter & Dart Essentials Training Document

1. Why Flutter? Flutter is an open-source UI toolkit created by Google for building beautiful, natively compiled, cross-platform applications for mobile, web, and desktop—all from a single codebase. Key benefits of Flutter: • Single Codebase: Write once, run on Android, iOS, Web, and Desktop. • Hot Reload: Allows real-time UI and logic changes without restarting the app. • Native Performance: Compiles to ARM code and uses Skia for rendering. • Rich UI: Comes with Material Design and Cupertino widgets for Android & iOS. • Strong Ecosystem: Supported by Google, growing community, and many open-source packages.
2. Flutter Architecture Flutter has a layered architecture that provides flexibility and high performance: • Framework Layer (Dart): Widgets, gestures, animations, rendering. • Engine Layer (C++): Skia graphics engine, text rendering, and plugin support. • Embedder Layer: Platform-specific APIs for Android, iOS, web, desktop.
3. Setting up Environment Steps to set up Flutter on Windows:
4. Download Flutter SDK from https://flutter.dev.
5. Extract and add Flutter bin folder to PATH.
6. Install Android Studio or VS Code for IDE support.
7. Install Android SDK, configure emulator.
8. Run flutter doctor to verify setup.

Steps to set up Flutter on macOS (iOS development):

1. Install Xcode from App Store.
2. Install Flutter SDK and configure PATH.
3. Install CocoaPods (sudo gem install cocoapods).
4. Run flutter doctor to verify setup.
5. Basic Project Structure Default structure: • lib/: Dart source code, contains main.dart. • android/: Android native code. • ios/: iOS native code. • pubspec.yaml: Manages dependencies, assets, fonts, and metadata.

Enterprise-level recommended structure: • core/: Common utilities, constants, themes. • data/: APIs, repositories, models. • domain/: Business logic, use cases. • features/: Each feature in its own module (e.g., login, dashboard, profile). • shared/: Shared widgets, components, services. 5. Dart Essentials Important Dart features: • Null Safety: Prevents null reference errors. Variables must be initialized or marked nullable with '?'. • Async & Await: Handles asynchronous programming using Futures and Streams. • Generics: Makes code reusable and type-safe (e.g., List, List). • Exception Handling: Use try-catch-finally with custom exception classes. 6. Hands-on Dart Refresher (with Solutions) Q1: Write a program to print Fibonacci sequence using async function. Solution: Future fibonacci(int n) async { int a = 0, b = 1; for (int i = 0; i < n; i++) { print(a); int temp = a + b; a = b; b = temp; await Future.delayed(Duration(milliseconds: 300)); } } void main() async { await fibonacci(10); }

Q2: Create a generic function to find maximum of two values. Solution: T maxValue(T a, T b) { return (a.compareTo(b) > 0) ? a : b; } void main() { print(maxValue(10, 20)); print(maxValue('apple', 'banana')); }

Q3: Implement exception handling in file operations. Solution: import 'dart:io';

void main() { try { File file = File('data.txt'); String contents = file.readAsStringSync(); print(contents); } catch (e) { print('Error reading file: $e'); } finally { print('Operation complete.'); } } 7. Flutter App Setup & Best Practices Recommended best practices: • Use Clean Architecture (separate UI, business logic, and data layers). • State Management: Use Provider, Riverpod, or Bloc pattern. • Organize project into features/modules for scalability. • Write unit tests, widget tests, and integration tests. • Maintain consistent naming conventions and folder structure. • Use Dart analysis options (linter rules) for code quality. 8. Mini App Exercise: Todo App (with Solution) Requirements:

1. Add tasks with title & description.
2. Show tasks in list with status.
3. Mark tasks completed.
4. Delete tasks.
5. Persist tasks using shared_preferences.

Solution (simplified example): import 'package:flutter/material.dart'; import 'package:shared_preferences/shared_preferences.dart'; import 'dart:convert';

void main() => runApp(TodoApp());

class TodoApp extends StatefulWidget { @override _TodoAppState createState() => _TodoAppState(); }

class _TodoAppState extends State { List<Map<String, dynamic>> tasks = [];

@override void initState() { super.initState(); loadTasks(); }

void loadTasks() async { final prefs = await SharedPreferences.getInstance(); String? data = prefs.getString('tasks'); if (data != null) { setState(() { tasks = List<Map<String, dynamic>>.from(json.decode(data)); }); } }

void saveTasks() async { final prefs = await SharedPreferences.getInstance(); prefs.setString('tasks', json.encode(tasks)); }

void addTask(String title) { setState(() { tasks.add({'title': title, 'done': false}); }); saveTasks(); }

void toggleTask(int index) { setState(() { tasks[index]['done'] = !tasks[index]['done']; }); saveTasks(); }

void deleteTask(int index) { setState(() { tasks.removeAt(index); }); saveTasks(); }

@override Widget build(BuildContext context) { return MaterialApp( home: Scaffold( appBar: AppBar(title: Text('Todo App')), body: ListView.builder( itemCount: tasks.length, itemBuilder: (context, index) { return ListTile( title: Text(tasks[index]['title']), trailing: IconButton( icon: Icon(Icons.delete), onPressed: () => deleteTask(index), ), leading: Checkbox( value: tasks[index]['done'], onChanged: (_) => toggleTask(index), ), ); }, ), floatingActionButton: FloatingActionButton( onPressed: () { showDialog( context: context, builder: (context) { TextEditingController controller = TextEditingController(); return AlertDialog( title: Text('New Task'), content: TextField(controller: controller), actions: [ ElevatedButton( onPressed: () { addTask(controller.text); Navigator.pop(context); }, child: Text('Add'), ) ], ); }, ); }, child: Icon(Icons.add), ), ), ); } }

Key Components of Flutter Development

1. Dart Language Fundamentals Flutter apps are written in Dart, so knowing its core features is essential: • Data Types o int, double, String, bool, dynamic • Collections o List (like arrays), Set, Map (key-value pairs) • Null Safety o ?, !, late keywords • Functions & Classes o Constructors, named parameters, optional parameters • Generics o List, Map<int, String> • Async Programming o Future, async/await, Stream • Exception Handling o try–catch–finally, custom exceptions

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2. Flutter Core Widgets Widgets are the building blocks of a Flutter UI. • Basic Widgets o Text, Container, Row, Column, Stack, ListView • Material Widgets (for Android look) o Scaffold, AppBar, FloatingActionButton, Drawer, SnackBar • Cupertino Widgets (for iOS look) o CupertinoButton, CupertinoNavigationBar • Input Widgets o TextField, Checkbox, Radio, DropdownButton, Slider • Layout & Positioning o Expanded, Flexible, Align, Padding, Center, SizedBox • Advanced Lists o ListView.builder, GridView, CustomScrollView

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3. State Management To manage app state (data flow + UI updates), Flutter provides: • setState (basic, local state) • Provider (Google-recommended for medium projects) • Riverpod (modern, better Provider) • Bloc / Cubit (enterprise-level, predictable state) • GetX / MobX (lightweight alternatives)

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4. Navigation & Routing • Navigator 1.0 (stack-based) → Navigator.push, Navigator.pop • Navigator 2.0 (declarative) → Good for large apps • Routing libraries: go_router, auto_route

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5. Theming & Styling • ThemeData for global app theme • Custom colors, fonts, and dark mode • Responsive UI with MediaQuery, LayoutBuilder

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6. Data & Persistence • Local Storage o shared_preferences (key-value store) o sqflite (SQLite DB) o hive (NoSQL DB, lightweight, fast) • Remote Data o http package (basic REST APIs) o dio package (advanced APIs with interceptors) o JSON serialization (manual / json_serializable)

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7. Asynchronous Programming • Futures → async tasks (API calls, DB ops) • Streams → continuous data (chat, notifications, sockets)

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8. Animations • Implicit animations: AnimatedContainer, AnimatedOpacity • Explicit animations: AnimationController, Tween, CurvedAnimation • Hero Animation for screen transitions • Lottie animations (JSON animations)

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9. Testing • Unit Tests → test Dart functions • Widget Tests → test UI components • Integration Tests → test whole app flow

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10. Dev Tools & Best Practices • Flutter DevTools (debugging, profiling) • Linting & Formatting (flutter_lints) • CI/CD with GitHub Actions, Codemagic, Bitrise • Code Splitting (modular project structure)

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Summerize: • Dart → Lists, Maps, async, exceptions • Widgets → UI building blocks • State Management → Provider, Bloc, etc. • Navigation → Routing system • Data Handling → APIs + Local storage • Styling → Themes & responsive UI • Testing + Tools → For enterprise readiness