State management approaches

Ephemeral state, sometimes called UI or local state, is neatly contained in a single widget — the current page in a PageView or the selected tab in a BottomNavigationBar. Other widget tree parts seldom access it, it needs no serialization, and it doesn't change in complex ways, so techniques like ScopedModel or Redux are unnecessary; a StatefulWidget with setState() suffices, as with a bottom navigation bar's _index field. App state, or shared state, is shared across many app parts and kept between user sessions — user preferences, login info, shopping carts. State and setState() can manage all app state, but complex cases warrant researching options. No clear-cut rule distinguishes the types; ephemeral state may need refactoring into app state as features grow. Scope: Flutter. Reviewed October 4, 2026.