Stateless vs Stateful widgets in Flutter
In Flutter, a widget is a building block for creating user interfaces. There are two types of widgets: StatefulWidget and StatelessWidget .The widgets are either StatefulWidget or StatelessWidget. The key difference between the two is whether or not they can change over time.
Stateless Widget
StatelessWidget is immutable, meaning its properties cannot change once created. It is only built once and then displayed on the screen and its appearance is determined solely by the values of its constructor arguments. These widgets are used for displaying static information such as text, icons, images, and other user interface elements.
To create a StatelessWidget, you need to create a class that extends the StatelessWidgetclass and implement the build() method. The build() method returns a Widget that describes how the widget should be displayed.
Here’s an example of a simple StatelessWidget which shows a static text:
Here’s another example of a StatelessWidget that displays a text
In this example, MyTextWidget is a StatelessWidget that takes a String parameter called text. In the build() method, it returns a Text widget that displays the text property.
You can use this widget in your app by creating an instance of MyTextWidget and passing in the text parameter
Stateful Widget
StatefulWidget, on the other hand, is dynamic and can change during runtime and resulting in a visual update to the UI. These widgets are used for displaying information that can change based on user interaction, network requests, or any other state changes. StatefulWidget can be updated multiple times during their lifetime, based on user interactions or changes to data. When the state of a StatefulWidget changes, the widget rebuilds its subtree. This allows the widget to reflect the updated state and change its appearance if necessary. When a StatefulWidget is first created, it creates an associated State object, which is responsible for managing the widget’s state.
As seen in the example above, _MyStatefulWidgetState is the State class, and it manages the _counter variable. The _incrementCounter() method updates the _counter variable and calls the setState() method to notify Flutter to rebuild the widget’s UI. The build() method returns the widget’s UI, which consists of a Scaffold with an AppBar, a Center with two Text widgets, and a FloatingActionButton that calls _incrementCounter() when pressed.
Stateless widgets vs Stateful widgets
Some differences between StatelessWidget and StatefulWidget are given below:
State management
The main difference between StatefulWidget and StatefulWidget that StatefulWidget can change its state during the lifetime of the widget, while StatelessWidget cannot. StatefulWidget is used for more complex UI elements that require internal state management, such as user input fields, animations, and navigation.
Immutability
StatelessWidgets are immutable, which means that once they are created, their properties cannot be changed. They are ideal for simple UI elements that don’t require any internal state management. In contrast, StatefulWidgets are mutable and can change their state during their lifetime.
Performance
Since StatelessWidgets are immutable and don’t change during the widget’s lifetime, they are more efficient than StatefulWidgets. StatefulWidgets, on the other hand, require more resources to maintain their internal state and manage their lifecycle.
Rebuild frequency
StatelessWidgets are typically built once and never updated, whereas StatefulWidgets are rebuilt whenever their internal state changes. This can have an impact on performance, as rebuilding a widget tree can be expensive.
Complexity
StatefulWidgets are more complex than StatelessWidgets due to their ability to manage the internal state. They require more code to manage their state, and this can make them more difficult to debug and maintain. However, this difference may not be noticeable in simple UIs with only a few widgets.
Usage:
StatelessWidgets are more suitable for UI elements that don’t need user input or interaction, while StatefulWidgets are more suitable for UI elements that require user input or interaction, such as forms, animations, and navigation.
The main advantage of using StatelessWidget over StatefulWidget is that it has a simpler lifecycle and is less prone to errors caused by state changes. Additionally, since StatelessWidget does not require a State, it is typically more efficient and consumes less memory.
Overall, choosing between StatefulWidget and StatelessWidget depends on the specific needs of your application. If you need to manage an internal state, use a StatefulWidget. If you don’t need to manage the internal state, use a StatelessWidget for better performance and simpler code.
