Flutter Journey 003 — Widgets in Flutter
In Flutter, widgets are the building blocks of the user interface (UI) of an app. They are the visual elements that users interact with, such as buttons, text fields, images, and more. Flutter uses a widget-based architecture, where the entire UI is composed of nested widgets, forming a tree-like structure called the widget tree.
A widget tree is a hierarchy of widgets that describes the user interface of an application. Every Flutter app has a widget tree, which is built by composing individual widgets to create more complex widgets.
A widget in Flutter is a self-contained element that represents a part of the user interface. A widget can be an icon, text input field, or even a complete screen. Widgets can be simple or complex, and they can be nested inside other widgets to create more sophisticated user interfaces.
The widget tree in Flutter is constructed using a declarative programming model, where the user interface is described using code that creates and composes widgets. When a widget is added to the tree, it becomes a child of its parent widget, and the parent widget is responsible for managing its child widgets.
The widget tree is important in Flutter because it defines the layout and appearance of the user interface. The Flutter framework uses the widget tree to render the user interface, and it updates the tree whenever the application state changes. This allows for fast and efficient rendering of the user interface, even for complex and dynamic applications.
Container, Form, Column, and so on, are widgets, A screen UI completes with the combination of widgets. And the combination of all these widgets forms a widget tree.
Widgets in Flutter are classified into two types: Stateless widgets and Stateful widgets.
Stateless Widgets
A stateless widget is a widget that does not have any mutable state. This means that once a stateless widget is built, it cannot be changed. Stateless widgets are used to represent parts of the user interface that do not change, such as static text, images, or icons.
Stateless widgets are simple and lightweight, and they are easy to use in Flutter. They can be created using a simple class that extends the StatelessWidget class. Stateless widgets only have one method that needs to be implemented, which is the build() method. The build() method is responsible for describing the widget's user interface, and it returns a widget tree that represents the user interface.
Because stateless widgets do not have any mutable state, they are easy to test and can be reused throughout an application. They are also efficient because they do not need to manage any state or handle any state changes. Overall, stateless widgets are a key building block of Flutter apps and are used extensively in most applications.
Stateful Widget
A stateful widget is a widget that can change its internal state during its lifetime. This means that a stateful widget can be updated and re-rendered based on changes in its state. Stateful widgets are used to represent parts of the user interface that can change dynamically, such as input fields, animations, or scrollable lists.
Stateful widgets are a bit more complex than stateless widgets. They require the implementation of two classes: a StatefulWidget class and a State class. The StatefulWidget class is responsible for creating the State object, and the State class is responsible for managing the widget’s mutable state.
The State object can be updated using the setState() method, which triggers a rebuild of the widget tree. This allows the stateful widget to update its appearance based on changes in its state.
Stateful widgets are more powerful than stateless widgets, but they are also more complex to use. They require careful management of the mutable state to ensure that the widget tree is updated correctly. However, when used correctly, stateful widgets can provide a rich and dynamic user interface for your Flutter app.
That's it. Thanks for reading.
