Flutter is a powerful framework for building cross-platform apps with a reactive UI. One of its core concepts is state management, and setState is the most basic way to handle local state changes.

What is setState ?
setState is a method provided by Flutter’s State class (used with StatefulWidget ). It tells Flutter that the widget’s internal state has changed and the UI needs to be rebuilt to reflect those changes.
Triggers a UI rebuild – Flutter re-renders the widget when setState is called.
Works only inside statefulWidget – StatelessWidgets cannot use setState.
Local state management – Best for small-scale state changes within a single widget.

When should you use setState ?
setState is ideal for managing local UI state – data or a small part of your app.

Common Use Cases:
Toggle buttons (e.g., show/hide a widget)
Counters (e.g., increment/decrement a value)
Form inputs (e.g., test field changes)
Animations (e.g., changing opacity or position)

How Does setState Work ?
When you call setState :
Flutter marks the widget as “dirty” (needs rebuild).
The build() method runs again.
The UI updates with the new state.

Important Notes:
Never call setState inside build() -> Leads to infinite loops!
Avoid heavy computations inside setState -> Can cause janky UI.