2.4. Development environment setup: Basic structure of a Flutter app

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Before we start developing apps using Flutter and Dart, we must set up our development environment. This setup involves several steps that ensure we have all the tools we need to build and test our applications.

The first step in setting up the development environment is to install the Flutter SDK. The Flutter SDK is the software development kit that contains all the libraries and tools we need to build Flutter apps. To install the Flutter SDK, we need to visit the official Flutter website and follow the installation instructions for our specific operating system.

After installing the Flutter SDK, the next step is to install the Dart SDK. The Dart SDK is the software development kit for the Dart programming language, which is the language used to write Flutter apps. We can install the Dart SDK from the official Dart website.

With Flutter and Dart SDKs installed, the next step is to configure our code editor. While we can use any code editor to develop Flutter apps, Flutter recommends using Android Studio, IntelliJ IDEA or Visual Studio Code. These code editors have built-in support for Flutter and Dart, which makes app development easier.

After setting up our code editor, we need to install the Flutter plugin. The Flutter plugin adds support for Flutter to our code editor, allowing us to build, run and debug Flutter apps directly from our code editor.

Now that our development environment is set up, we can start developing our first Flutter app. The basic structure of a Flutter application consists of several components.

The first component is the 'main.dart' file. This is the entry point for our Flutter app. It contains a main function that creates an instance of our application and runs it. The main function is also where we set our app's theme and any global settings.

The next component is the 'App' class. This is the main class of our application. It inherits from the 'StatelessWidget' or 'StatefulWidget' class, depending on whether our application is stateful or not. The 'App' class contains a 'build' method that returns our application's widget tree.

Widgets are the basic building blocks of a Flutter app. Each widget in Flutter is an immutable class that describes part of our app's UI. Widgets can be as simple as text or a button, or as complex as a scrollable list or grid layout.

To create our application's user interface, we combine widgets to form a widget tree. The root of the widget tree is the 'App' widget, and each widget in the tree can have any number of child widgets.

Last but not least, we have the state of our application. State is information that may change during the lifetime of our application. In Flutter, we manage state by creating classes that inherit from 'State'. Each widget that wants to manage state must be a subclass of 'StatefulWidget' and must override the 'createState' method to create an instance of its state.

In short, to build Flutter apps, we need to set up our development environment, understand the basic structure of a Flutter app, and learn how to work with widgets and state. With this knowledge, we are ready to start developing Flutter applications from zero to advanced.

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72.5. Development Environment Setup: Flutter Widgets and Basic Elements