Stateful and Stateless Widgets in Flutter (2024)

FAQs

What is the difference between stateful and stateless performance in Flutter? ›

While stateless widgets focus on rendering static content, stateful widgets bring interactivity and dynamism to your Flutter app. Stateful widgets have an associated mutable state that can change over time, allowing you to update the UI based on user interactions, data changes, or other triggering events.

One efficient way to pass data to a StatefulWidget is through its constructor. By doing so, the data is readily available as soon as the widget is created. For instance, you can define the necessary data as parameters in the widget's constructor.

It holds a mutable state which we can change and reflect on UI during the next build method trigger. This is the reason we have two different classes for the Stateful widget so even with an immutable widget we can take advantage of a mutable state to reflect UI changes. State property can be easily accessed directly.

Stateful widgets are useful when the part of the user interface you are describing can change dynamically, e.g. due to having an internal clock-driven state, or depending on some system state.

There are two types of widgets: stateless and stateful.

Scalability: Stateless applications are generally more scalable, as each request is independent and can be handled by any available server. Stateful applications may require more complex mechanisms for load balancing and session management.

The widgets whose state can not be altered once they are built are called stateless widgets. These widgets are immutable once they are built i.e. any amount of change in the variables, icons, buttons, or retrieving data can not change the state of the app. Below is the basic structure of a stateless widget.

A stateful widget is dynamic: for example, it can change its appearance in response to events triggered by user interactions or when it receives data. Checkbox , Radio , Slider , InkWell , Form , and TextField are examples of stateful widgets. Stateful widgets subclass StatefulWidget .

Examples of Stateless widgets are Icon, IconButton, and Text. In the code snippet above, MyStatelessWidget extends StatelessWidget and overrides the build method. The build method describes the user interface part represented by this widget.

Stateless widgets are ideal for static content and reusable components, while stateful widgets shine when dealing with user interactions, dynamic data, and complex UI behavior. To build efficient and performant Flutter apps, it's crucial to understand the characteristics and use cases of both types of widgets.

Can a stateful widget have multiple states? ›

Because a given StatefulWidget instance can be inflated multiple times (e.g., the widget is incorporated into the tree in multiple places at once), there might be more than one State object associated with a given StatefulWidget instance.

One way to reinitialize a stateful widget is to call the setState() method. This method tells Flutter to rebuild the widget with the updated state. However, this will only rebuild the widget itself, not its children. Another way to reinitialize a stateful widget is to use the reInitialize() method.

Stateful widgets are widgets that maintain their state over time. This means that they can remember information from one moment to the next. For example, a stateful widget might remember the user's current location in a map application.

Stateful apps use persistent data storage to record all user conversations, interactions, and transactions so that they can return to the customer conversation without having to start from scratch. Stateful application examples include: Digital shopping carts that record what you put in them.

Immutability of StatefulWidget: The StatefulWidget class is typically immutable, meaning its properties cannot be changed once the widget is created. Placing the build method in State allows the StatefulWidget to remain immutable while still allowing the UI representation to be rebuilt when needed.

Stateful apps save client session data on the server, providing historical context and faster processing. In contrast, stateless apps don't save client session data on the server and rely on externalized state data.