Building Apps with Flutter

1. Introduction

Flutter is an open-source UI toolkit created by Google for building natively compiled applications for mobile, web, and desktop from a single codebase. This tutorial aims to introduce you to Flutter and guide you in creating your first Flutter application.

By the end of this tutorial, you will have a basic understanding of:

• Flutter's architecture
• Flutter's widget system
• How to set up a Flutter development environment
• How to create a basic Flutter app

Prerequisites:
- Basic knowledge of programming concepts
- Familiarity with Dart language (not mandatory but beneficial)

2. Step-by-Step Guide

Flutter's Architecture:

Flutter uses Dart, which is a client-optimized language for developing fast apps on any platform. The architecture of Flutter is based on the following key principles:

• Everything in Flutter is a widget
• Widgets describe what their view should look like given their current configuration and state
• Widgets are composed to form the app's UI

Setting up Flutter Environment:

1. Download the latest stable Flutter SDK from the Flutter website.
2. Extract the zip file and add Flutter tool to your path.
3. Run the following command to check for any dependencies you may still need to install to complete the setup:

flutter doctor

Creating a New Flutter Project:

1. Open terminal or CMD
2. Navigate to the directory where you want to save the project
3. Run the following command:

flutter create project_name

1. Navigate into your new project directory:

cd project_name

1. To start the app, you can run:

flutter run

Flutter Widgets:

In Flutter, everything is a widget. Widgets are the basic building blocks of the app’s user interface. They take in configuration details and the current state, and provide a descriptive view.

class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      title: 'Flutter Demo',
      theme: ThemeData(
        primarySwatch: Colors.blue,
      ),
      home: MyHomePage(title: 'Flutter Demo Home Page'),
    );
  }
}

3. Code Examples

Here's an example of a simple Flutter app:

import 'package:flutter/material.dart';

void main() {
  runApp(MyApp());
}

class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      title: 'Welcome to Flutter',
      home: Scaffold(
        appBar: AppBar(
          title: Text('Welcome to Flutter'),
        ),
        body: Center(
          child: Text('Hello World'),
        ),
      ),
    );
  }
}

In the above code:

• runApp() function takes the given Widget and makes it the root of the widget tree.
• MyApp class is creating a Widget which contains a MaterialApp.
• MaterialApp is a convenience widget that provides many widgets that follow the Material Design guidelines.
• Scaffold is another convenience widget that provides a default app bar, title, and a body property that holds the widget tree for the home screen.

The output of the above code will be a simple app with a title and a body containing "Hello World".

4. Summary

In this tutorial, we learned about Flutter, its architecture, widgets, and how to set up a Flutter development environment. We also created a basic Flutter app.

Next, you might want to learn more about the Dart programming language, or dig deeper into Flutter widgets. The official Flutter website is a great resource for this.

5. Practice Exercises

1. Change the text 'Hello World' to 'Welcome to Flutter' and the app title to 'My First Flutter App'.
2. Add a second screen to the app that navigates on the press of a button and displays 'Second Screen' on a new page.
3. Create an app that displays a list of ten items.

Remember, learning by doing is the best way to understand and grasp new concepts. So, keep practicing!

Happy coding!