Flutter – a powerful framework for building apps on Android and iOS

What is Flutter?

Flutter is a framework created by Google that allows you to create mobile, web and desktop applications from a single source code, using different compilation methods depending on the platform. On Android and iOS, the code is compiled to native machine code (AOT – Ahead-of-Time), ensuring high performance. For web applications, Flutter renders the user interface using the CanvasKit engine (based on Skia) or a standard HTML/CSS renderer, instead of generating JavaScript code. On desktop systems, on the other hand, it uses native compilation to machine code, customized for the particular operating system (e.g. Windows, macOS, Linux).

Flutter is based on the Dart language and uses Skia’s own rendering engine, ensuring consistent UI quality across platforms. With its Hot Reload mechanism, it allows for quick code iterations, speeding up the application development process. Flutter offers a rich set of pre-built widgets compatible with Material Design and Cupertino, supports integration with native APIs and enables the creation of high-performance user interfaces.

What is a Dart and how does it work with Flutter?

Dart is a modern, object-oriented programming language created by Google, which is the foundation of Flutter. It is designed for efficient user interface development (UI-first programming) and optimized for cross-platform application development.

Dart uses two compilation methods:

• Ahead-of-Time (AOT) – used in production versions, compiles code to native machine code, which ensures high application performance.
• Just-in-Time (JIT) – used in developer mode, allows code to be dynamically run and modified while the application is running. With Hot Reload, code changes can be seen immediately without having to restart the application.

With support for asynchronous programming (Future, async/await, Stream) and strong typing, Dart allows you to easily manage state and perform network operations without blocking the user interface. Combined with Flutter, it enables development of Android, iOS, web and desktop applications, maintaining code and interface consistency across platforms.

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What does Flutter’s architecture look like?

Flutter’s architecture is organized into layers, each of which performs a specific function.

1. Flutter (Dart) application – Application code written in Dart language, defining the user interface and application logic. This is the top-level layer where developers create widgets and implement the application’s behavior.

2. Flutter Framework – A reactive framework written in Dart, consisting of several layers:

• core classes and services – These provide abstractions for animation, painting, gesture handling and other core application functionality.
• widget layer – This is responsible for widget definition and composition. Widgets in Flutter are a description of the user interface and follow a reactive programming model.
• Elements and RenderObjects layer – Elements manage the hierarchy and status of widgets, while render objects (RenderObjects) are responsible for actually drawing the interface on the screen. It is thanks to this layer that Flutter can dynamically update the appearance of the application in response to status changes.
• Material and Cupertino libraries – They contain ready-made user interface components in accordance with Material Design (Google) and Cupertino (Apple), which facilitates the creation of applications that comply with the platform guidelines.

3. Flutter engine – Written primarily in C++, it is responsible for rasterizing scenes using the Skia graphics engine. It also handles Flutter’s core API, including text layout, file and network input/output, accessibility and plugin system. In addition, it manages the execution environment and compilation of Dart code.

4. Embedder – A platform-specific component that allows Flutter applications to integrate with the operating system. It is responsible for running the application, handling event loops, managing the rendering surface and communicating with the operating system’s native APIs via Platform Channels. Embedder is written in platform-specific languages, such as Java/Kotlin and C++ for Android, Swift/Objective-C for iOS and macOS, C++ for Windows and Linux.

graphic source: https://docs.flutter.dev/resources/architectural-overview

How does Flutter compare to the competition?

Flutter is one of the most popular frameworks for developing cross-platform applications, but it is worth comparing with other technologies such as React Native and Kotlin Multiplatform.

Flutter vs. Kotlin Multiplatform (KMP)
Kotlin Multiplatform is an approach by Google and JetBrains that allows business logic to be shared between Android, iOS and other platforms, but the UI still has to be written natively. Unlike Flutter, KMP does not provide its own UI framework, which means developers must write interfaces separately for each platform. Flutter wins in terms of faster development and UI consistency, while KMP is a better choice if deep integration with native system features is a priority.

Flutter vs. React Native
React Native, developed by Facebook (Meta), also allows you to create Android and iOS apps from a single code, but uses JavaScript/TypeScript and native UI components. Unlike Flutter, which renders the UI in its own Skia engine, React Native relies on native operating system components. Flutter typically offers better performance and consistent application design across platforms, but React Native may have an advantage in integrating with the ecosystem of JavaScript and popular frontend libraries. If you want to explore this topic in more depth, we recommend our article Flutter vs. React Native

Why develop applications using Flutter?

Flutter is a cutting-edge cross-platform solution that allows fast and efficient development of mobile applications, eliminating the need to write separate versions for Android and iOS. Thanks to the common source code, developers can significantly reduce development time, which translates into resource savings for both companies and investors. The Dart language on which Flutter is based features an intuitive syntax, which makes it easy to learn, and a well-designed framework allows newcomers to be quickly deployed to work on projects. An additional advantage is the significant cost reduction, since almost the entire application is created from a single code, which minimizes maintenance and development expenses. Flutter also offers a Hot Reload feature, which allows users to instantly preview code changes without having to restart the application, speeding up testing and corrections. The technology has a low entry threshold and is completely free, which makes more and more developers and companies decide to use it. In addition, Flutter offers a rich library of widgets, allowing to quickly create attractive and functional user interfaces without the need for native system components.

Advantages of Flutter

Multi-platform – Enables development of Android, iOS, Web and desktop applications from a single code, saving time and cost.

Performance – Ahead-of-Time (AOT) compilation ensures smooth and fast application performance.

Rich ecosystem – A broad package base and an active community facilitate application development.

Consistent interface – Built-in Material Design and Cupertino widgets allow for an attractive and consistent UI across platforms.

Flutter’s future

One of the key developments is to improve performance and further optimize AOT and JIT compilation, which will allow applications to run even faster. Google is also investing in Flutter for Web to make it a viable alternative to classic frontend technologies.

Fuchsia OS, the new operating system from Google, uses Flutter as its main framework for application development, but its market adoption remains limited. While Flutter may play an important role in the Fuchsia ecosystem in the future, at this point its position in cross-platform development is mainly due to its broad community support, large number of ready-made libraries and integration with popular systems such as Android, iOS, Web and desktop.

Users’ most common questions

What is Flutter and what is it used for?
Flutter is a framework developed by Google for creating mobile, web and desktop applications from a single source code. It is used for its high performance, Hot Reload and consistent user interface.

Is Flutter a programming language?
No, Flutter is a framework. The language used for programming in Flutter is Dart.

What is Flutter best suited for?
Flutter is best suited for developing mobile apps for Android and iOS as well as cross-platform apps for web and desktop.

Is Flutter Python?
No, Flutter and Python are different technologies. Flutter uses the Dart language, while Python is a separate programming language.

Does Flutter use C++?
Yes, the Flutter engine (Skia) and its low-level components are written in C++, but the application code is written in Dart.

Is Flutter faster than Python?
Yes, Flutter is faster than Python in mobile applications and user interfaces because it uses AOT compilation for native machine code.