The basics of Flutter

Discover the basics to understand how Flutter. Learn the key concepts programming languageand much more.

To master the powerful Flutter tool, it's essential to understand its fundamentals. In this article, we'll take you through the basics of how Flutter works. We'll explore the key principles behind this revolutionary technology for cross-platform application development. Whether you're a seasoned developer or a novice in the field, this reading will give you a better understanding of Flutter and its essential functionalities. Get ready to dive into the world of Flutter and discover new perspectives on application development.

What is Flutter?

Definition

Flutter is an open-source framework developed and maintained by Google. It allows you to create mobile applications for iOS, Android and other platforms from a single source code. With Flutter, developers can build attractive, responsive user interfaces, smooth animations, and easily manage the state of their application.

History

Flutter was first announced by Google in 2015 and entered alpha release in 2017. Since then, it has seen rapid adoption in the developer community thanks to its high performance and productivity. Flutter has been used to create many popular applications, such as Google AdsAlibaba, Hamilton, and many others.

Objectives

Flutter's main objectives are to simplify cross-platform application development, improve application performance and responsiveness, and deliver a high-quality user experience. Flutter also aims to enable developers to easily customize the appearance and behavior of their applications, while offering great flexibility in managing application state.

Flutter's key concepts

Widgets

Widgets are the basic elements of Flutter and represent everything visible in an application's user interface. Every element, from a simple button to the application's main screen, is a widget. Widgets can be combined and prioritized to form complex user interfaces.

La notion de “tout est un widget”

La philosophie fondamentale de Flutter est que “tout est un widget”. Cela signifie que chaque élément de l’interface utilisateur est représenté par un widget, y compris les éléments plus complexes tels que les polices, les styles, les mises en page et les interactions utilisateur. Cette approche simplifie la construction et la personnalisation des interfaces utilisateur.

The rendering engine

Flutter uses its own rendering engine to display user interfaces smoothly and responsively. Flutter's rendering engine, called Skia, is optimized to deliver high performance and smooth animations. It also provides precise control over the graphics and rendering of user interface elements.

The responsiveness framework

Flutter's reactivity framework manages UI updates in response to application state changes. When a state changes, Flutter updates the relevant widgets efficiently, minimizing unnecessary recalculations. This ensures high performance even for complex user interfaces.

Flutter's programming language

Dart

Flutter uses Dart as its main programming language. Dart is a modern, high-performance language developed by Google, designed specifically for the development of mobile and web applications. Dart offers clear, concise syntax, fast compilation and support for advanced features such as static typing and asynchronous futures.

Dart features

Dart offers a number of features that make it ideally suited to the development of Flutter applications. These include object-oriented syntax, the ability to define classes and interfaces, asynchronous state management thanks to futures and Streams, the ability to create anonymous (lambda) functions and closures, and support for multiple inheritance thanks to mixins.

Comparison with other languages

Compared with other languages commonly used for mobile development, such as Java, Kotlin and Objective-C/Swift, Dart offers several advantages. In addition to its high performance, Dart offers increased productivity thanks to its fast compilation and optional dynamic typing. What's more, Dart's clear, concise syntax makes code easier to read and understand, reducing the risk of errors and speeding up development.

Application development with Flutter

Installing Flutter

To start developing applications with Flutter, you first need to install the Flutter SDK (Software Development Kit). The Flutter SDK is available free of charge and can be downloaded from the official Flutter website. Once the SDK has been installed, it is necessary to configure the development environment.

Development environment configuration

Flutter is compatible with various IDE (Integrated Development Environment), such as Android StudioIntelliJ IDEA and Visual Studio Code. It is recommended to use an IDE adapted to Flutter, as it facilitates development and offers advanced features such as code completion, debugging and dependency management.

Once you've installed an IDE with the Flutter plug-in, you'll need to configure the path to the Flutter SDK and development tools. This step enables the IDE to recognize Flutter and provide Flutter-specific functionality.

Creating a Flutter project

Once the development environment has been set up, it is possible to create a Flutter project. This can be done from the IDE using a basic project template provided by Flutter, or by using the Flutter command line. When a Flutter project is created, a set of files and directories is generated, providing a basic structure for application development.

Flutter project structure

La structure d’un projet Flutter est basée sur le modèle de conception MVC (Modèle-Vue-Contrôleur). Le code source de l’application se trouve dans le répertoire “lib” du projet. Ce répertoire contient les fichiers source Dart de l’application, y compris les fichiers de modèle, de vue et de contrôleur. Il peut également contenir d’autres répertoires pour organiser le code de manière logique.

Navigation between screens

Visit navigation entre les écrans est une partie importante du développement d’applications Flutter. Flutter offre plusieurs solutions pour gérer la navigation, telles que le “Navigator” intégré, qui permet de pousser et de popper des écrans sur une “pile” de navigation. Il existe également des bibliothèques tierces, telles que “flutter_bloc” et “GetX”, qui facilitent la gestion de la navigation et la communication entre les écrans.

Creating user interfaces with Flutter

Basic widgets

Flutter offers a wide range of ready-to-use widgets for creating attractive, functional user interfaces. Basic widgets include buttons, dialogs, images, text fields, lists and much more. These widgets can be customized and arranged to create user interfaces tailored to the needs of the application.

Creating layouts

Flutter offre plusieurs widgets pour créer et organiser des layouts. Parmi ces widgets, on trouve “Container”, qui permet de définir la taille, la marge et la couleur d’un élément, “Row” et “Column”, qui permettent de créer des layouts linéaires, et “Stack”, qui permet de superposer des éléments les uns sur les autres. Ces widgets peuvent être combinés et hiérarchisés pour créer des interfaces utilisateur complexes.

User interaction management

Flutter offers a number of features for managing user interaction, such as gesture detection and interaction animations. With Flutter, it's possible to detect gestures such as taps, swipes and swipes, and trigger corresponding actions. Fluid animations can also be created to make user interactions more visually pleasing.

Themes and styles

Flutter offers a system of themes and styles that allow you to customize the application's appearance in a consistent way. Themes define the colors, fonts and other elements of the user interface, while widget-specific styles allow you to customize their individual appearance. This creates a consistent, professional user experience across the entire application.

State management in Flutter

The concept of state

State management is important in any application, and Flutter offers several approaches to managing state effectively. State represents data that can change during application execution, such as the text in an input field or the status of a button. Flutter offers solutions for managing local and global state in a clear and organized way.

Local government management

Pour gérer l’état local, Flutter propose différents widgets tels que “StatefulWidget” et “Provider”. Ces widgets permettent de définir des états locaux qui peuvent être modifiés au cours de l’exécution de l’application. Lorsqu’un état local change, Flutter met à jour automatiquement les widgets concernés pour refléter les nouvelles données.

Global condition management

La gestion de l’état global se fait généralement à l’aide de bibliothèques tierces telles que “Provider”, “Redux” ou “Riverpod”. Ces bibliothèques permettent de partager l’état entre différents widgets et d’assurer une gestion centralisée de l’état global. Cela facilite la communication entre les widgets et garantit que les changements d’état sont pris en compte dans l’ensemble de l’application.

The different approaches

Il existe plusieurs approches pour gérer l’état dans Flutter, chacune ayant ses avantages et ses limitations. Certains développeurs préfèrent utiliser des solutions simples telles que “setState” pour gérer l’état local, tandis que d’autres préfèrent utiliser des bibliothèques tierces plus puissantes pour gérer l’état global. Le choix de l’approche dépend des besoins spécifiques de l’application et des préférences du développeur.

Animations in Flutter

Basic animations

Animations are essential to make an application more attractive and interactive. Flutter offers native support for basic animations such as transition animations, keyframe animations, rotation animations, scaling animations and many more. These animations can be implemented using various widgets and methods provided by Flutter.

Complex animations

In addition to basic animations, Flutter also offers advanced features for creating complex animations. These include custom animation, which lets you create customized animations using custom interpolation curves, compound animation, which lets you combine several animations to achieve more complex effects, and physical animation, which simulates physical movements such as gravity and friction.

Managing transitions

Flutter also offers tools for managing transitions between different pages or screens within an application. For example, it is possible to animate the transition between two screens using effects such as crossfading, expansion or rotation. These transitions make for a smoother, more pleasant user experience.

Integration of external services and APIs

Access to external resources

Dans le développement d’applications, il est souvent nécessaire d’accéder à des ressources externes telles que des bases de données, des fichiers locaux, des capteurs ou des services en ligne. Flutter offre une prise en charge native pour accéder à ces ressources grâce à des bibliothèques spécifiques. Par exemple, il est possible d’accéder aux fichiers locaux en utilisant “path_provider” ou de consommer des API en utilisant “http”.

Communication with APIs

Flutter facilite la communication avec les API en offrant un support natif pour les protocoles de communication courants comme HTTP et WebSocket. Il existe des bibliothèques tierces telles que “dio” qui simplifient encore plus la communication avec les API en fournissant des fonctionnalités avancées telles que la gestion des intercepteurs, le caching, et la gestion des erreurs.

Common integration libraries

To facilitate integration with popular third-party services, Flutter offers a rich ecosystem of integration libraries. For example, there are libraries for integrating authentication services such as Firebase Auth, geolocation services such as Geolocator, or analytics services such as Firebase Analytics. These libraries save development time by offering well-tested, pre-built functionality.

Deploying Flutter applications

The different deployment platforms

Flutter enables applications to be deployed on different platforms, including iOS, Android, the web, and even embedded systems such as Linux and macOS. For each platform, Flutter offers a specific set of tools and features to ensure an optimal user experience. It is also possible to customize the look and feel of the application for each platform.

Generating executable files

Flutter generates executable files for each target platform. For example, for iOS, Flutter generates an IPA file that can be distributed via the App Store, while for Android, Flutter generates an APK file that can be distributed via the Google Play Store. For web deployment, Flutter generates a set of HTML, CSS and JavaScript which can be hosted on a web server.

Testing and validation

Avant de déployer une application, il est important de la tester et de la valider pour garantir sa qualité et son bon fonctionnement. Flutter offre un ensemble d’outils pour faciliter les tests unitaires et d’intégration, ainsi que des outils pour la validation de l’application, tels que “flutter doctor”, qui vérifie les dépendances et les configurations requises. Ces outils permettent d’identifier et de résoudre les problèmes potentiels avant le déploiement.

Application stores

To distribute a Flutter application, it is often necessary to publish it on official application stores such as the Apple App Store and Google Play Store. Flutter offers native support for these stores, making it easy to submit and publish the application. Once published, the application is visible and accessible to users, who can download and install it on their devices.

Good development practices with Flutter

Recommended software architecture

Flutter ne dicte pas d’architecture spécifique, mais il existe des architectures recommandées pour développer des applications Flutter de manière structurée et maintenable. Parmi les architectures couramment utilisées, on trouve l’architecture de type “BLoC” (Business Logic Component), où la logique métier est séparée de la logique d’interface utilisateur. D’autres architectures, telles que “MVVM” (Model-View-ViewModel) ou “Clean Architecture”, peuvent également être utilisées en fonction des besoins spécifiques de l’application.

Code organization

Code organization is important for the readability and maintainability of a project. Flutter recommends organizing code using a logical project structure, such as separating source files according to their role (models, views, controllers), or using specific directories for features or application modules. The use of best practices such as breaking down code into reusable widgets and clear code documentation also contribute to better code organization.

Unit and integration testing

Testing is essential to guarantee the quality and stability of a Flutter application. Flutter offers native support for unit and integration tests, making it easy to write and run automated tests. Unit tests verify the correct operation of individual application components, while integration tests test the behavior of the application as a whole. Writing regular tests and executing automated tests contribute to the reliability of the application and the reduction of bugs.

Performance management

La gestion de la performance est importante pour garantir une expérience utilisateur fluide et réactive. Flutter offre plusieurs fonctionnalités pour optimiser les performances de l’application, telles que la compilation “ahead-of-time” pour réduire le temps de lancement de l’application, la mise en cache des widgets et des ressources, et la gestion efficace de l’état. Les bonnes pratiques de développement, telles que l’évitement des opérations coûteuses, l’utilisation de la gestion de la mémoire, et l’optimisation des animations, contribuent également à améliorer les performances de l’application.

In conclusion, Flutter is a powerful and versatile framework for cross-platform application development. Thanks to its key concepts such as widgets, the Dart language, state management, animations and integration of external services, Flutter offers a fluid and productive development experience. Using recommended best development practices, developers can create high-performance, attractive applications for a wide range of platforms.