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Flutter – Architecture Application

Flutter architecture primarily consists of the following components:

Widgets​

Widgets are the foundational building blocks of any Flutter application. They serve as the user interface (UI) elements that users interact with. A Flutter application itself is a widget composed of a hierarchy of smaller widgets.

In a standard application:

  1. Root Widget: Defines the application's overall structure.

  2. MaterialApp: Manages internal components and sets the application's properties.

  3. Scaffold: Contains the visible UI components. It has two primary properties:

    • AppBar: Defines the application's app bar.
    • Body: Contains the main content and child widgets.

Below is a conceptual hierarchy of a Flutter application:

Flutter Widget Hierarchy

The Center widget often wraps its content, defined through the child property, which could be a Text widget or other UI components.

Layers​

The Flutter framework is organized into layers, each representing a different level of complexity. These layers are stacked on top of one another:

  1. Platform-Specific Widgets: Widgets tailored to the operating system (Android or iOS).

  2. Native Flutter Widgets: Structural UI components, gesture detectors, and state management widgets.

  3. UI and State Layer: Handles rendering and visual components.

  4. Animation Layer: Manages transitions, gestures, and image flow.

  5. System Design Layer: High-level system interactions.

The below diagram gives an overview of the same:

Gestures​

Gestures are how users physically interact with a Flutter application. These include:

  • Tapping
  • Dragging
  • Swiping

Flutter uses GestureDetector, an invisible widget, to process these interactions. Developers can use gestures creatively to enhance the user experience by mapping them to desired actions.

Concept of State​

State in Flutter refers to data objects that determine a widget's behavior. It operates similarly to the concept of state in React.js. Flutter uses StatefulWidget to manage state, allowing specific widgets to re-render when their state changes without affecting the entire application.

Key Points:​

  • StatefulWidget: Used for components that require dynamic changes based on user interaction.
  • StatelessWidget: Used for components with static content that doesn't change.

Summary​

Flutter's architecture combines small and large widgets, working together to build applications. Each layer and component contributes to the framework's simplicity in development and its core complexity.

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