When to Use Stateful Widgets?

In Flutter, everything you build revolves around widgets. These widgets fall into two categories: Stateless and Stateful.

Stateless Widgets are immutable and don’t change once created.
Stateful Widgets, on the other hand, can hold and update state during their lifetime.

The challenge most beginners face is deciding when to use Stateful Widgets instead of Stateless ones. If you overuse Stateful Widgets, your app may become unnecessarily complex and heavy. If you underuse them, you’ll struggle to make your app interactive and dynamic.

This article will guide you through the scenarios where Stateful Widgets are necessary, using practical examples, best practices, and real-world cases.

Understanding Stateful Widgets

A Stateful Widget in Flutter is:

A widget that can change over time due to user interaction, animations, or data updates.
Built from two classes:
1. The StatefulWidget → immutable widget definition.
2. The State class → mutable object that stores the widget’s state.

Whenever the state changes, you call setState(), which triggers Flutter to rebuild the UI.

Why Use Stateful Widgets?

You should use Stateful Widgets whenever your app requires dynamic changes.

Typical reasons include:

User interactions (forms, text inputs, toggles).
Real-time updates (API calls, database changes).
Animations and transitions.
Any UI element that should change during the widget’s lifecycle.

When to Use Stateful Widgets – Key Scenarios

Let’s dive into the most common scenarios where Stateful Widgets are essential.

1. Forms and User Inputs

Forms are one of the most common use cases for Stateful Widgets.

A TextField where the user types input.
A Checkbox that toggles between checked and unchecked.
A RadioButton group where the selected option changes.

Example: TextField

class LoginForm extends StatefulWidget {
  @override
  _LoginFormState createState() => _LoginFormState();
}

class _LoginFormState extends State<LoginForm> {
  String email = "";

  @override
  Widget build(BuildContext context) {
return Column(
  children: &#91;
    TextField(
      onChanged: (value) {
        setState(() {
          email = value;
        });
      },
      decoration: InputDecoration(labelText: "Email"),
    ),
    Text("Entered Email: $email"),
  ],
);  }
}

Here:

The text field updates the email variable in real time.
The widget must be Stateful to react to input changes.

2. Counters and Incrementing Values

The classic Flutter example is a counter app.

Every time you press a button, the number increases.
This requires a Stateful Widget because the UI must change dynamically.

Example: Counter

class CounterWidget extends StatefulWidget {
  @override
  _CounterWidgetState createState() => _CounterWidgetState();
}

class _CounterWidgetState extends State<CounterWidget> {
  int count = 0;

  void increment() {
setState(() {
  count++;
});  }

  @override
  Widget build(BuildContext context) {
return Column(
  mainAxisAlignment: MainAxisAlignment.center,
  children: &#91;
    Text("Count: $count"),
    ElevatedButton(
      onPressed: increment,
      child: Text("Increment"),
    ),
  ],
);  }
}

Every button press calls setState(), which rebuilds the widget with the new count.

3. Animations

Animations are inherently stateful because they evolve over time.

Animating a button size when clicked.
Sliding in a menu.
Fading text in and out.

Flutter provides powerful animation libraries, but at the core, most animations require Stateful Widgets to keep track of changes in progress.

4. Data That Changes Dynamically

Any time your UI depends on changing data, you need Stateful Widgets.

Examples:

Live score updates in a sports app.
Real-time stock prices.
Weather data fetched from an API.
Chat messages that update as they arrive.

Example: API Data Update

class WeatherWidget extends StatefulWidget {
  @override
  _WeatherWidgetState createState() => _WeatherWidgetState();
}

class _WeatherWidgetState extends State<WeatherWidget> {
  String temperature = "Loading...";

  void fetchTemperature() async {
await Future.delayed(Duration(seconds: 2));
setState(() {
  temperature = "25°C";
});  }

  @override
  void initState() {
super.initState();
fetchTemperature();  }

  @override
  Widget build(BuildContext context) {
return Text("Temperature: $temperature");  }
}

Here:

Initially shows “Loading…”.
After fetching data, updates to “25°C”.
Requires Stateful because the value changes over time.

5. Toggles, Switches, and Checkboxes

Switches and toggles naturally require Stateful Widgets.

A Switch that turns on and off.
A Checkbox that changes between checked and unchecked.
A Favorite button (heart icon) that toggles state.

These require mutable state to track user preferences.

6. Interactive Lists and Navigation

Some lists or screens require dynamic behavior:

A list that loads more items when scrolled.
A shopping cart where items are added/removed.
A chat screen where new messages appear.

Such features cannot be built with Stateless Widgets alone.

When NOT to Use Stateful Widgets

It’s equally important to know when not to use Stateful Widgets:

Static UI → Titles, headers, decorative text.
Logos and icons that never change.
One-time widgets that don’t depend on input.

Rule of Thumb:
If your widget only displays static content, prefer a Stateless Widget.

Best Practices with Stateful Widgets

Keep Stateful Widgets Small
- Don’t make your entire screen a single Stateful widget.
- Instead, split into smaller widgets where only dynamic parts are Stateful.
Use initState() for Setup
- Place initialization logic (like fetching data) in initState().
Dispose Resources in dispose()
- Always close controllers, streams, and animations to prevent memory leaks.
Don’t Overuse setState()
- Only call setState() when the actual UI needs updating.
Prefer Stateless for Static UI
- Even within a Stateful widget, use smaller Stateless widgets for parts of UI that never change.

Real-World Examples of Stateful Widgets

Example 1: Login Screen

Email and Password inputs → Stateful.
“Login” button → Triggers state changes (loading, error, success).

Example 2: E-Commerce App

Product grid → Stateless (static data).
Cart icon with item count → Stateful.
Wishlist toggle (heart button) → Stateful.

Example 3: Chat App

Message input → Stateful.
Live messages → Stateful.
App header → Stateless.

Common Mistakes Beginners Make

Making everything Stateful
- Increases complexity and rebuild times.
Not separating UI and state
- Business logic inside the UI can lead to messy code.
Forgetting lifecycle methods
- Not disposing resources like controllers causes memory leaks.
Rebuilding entire screens unnecessarily
- Use proper state management to rebuild only what’s necessary.

Alternatives to Stateful Widgets

For larger apps, managing state with only Stateful Widgets becomes difficult. Flutter offers state management solutions like:

Provider
Riverpod
BLoC (Business Logic Component)
Redux
GetX

These tools help manage state across multiple widgets and screens efficiently.

Thinking in Stateful Widgets

When deciding whether to use Stateful Widgets, ask:

Does this widget depend on data that changes?
- If yes → Stateful.
- If no → Stateless.

This simple question helps you make the right choice.