All 7 Navigation & Routing in Flutter questions
More in Navigation & Routing in Flutter
How do the basic Navigator.push and Navigator.pop methods let you navigate to a new screen and then properly return back to the previous screen? How can you properly pass a result value back to the previous screen when calling Navigator.pop, such as returning a genuinely selected item from a picker screen? What is the difference between Navigator.push, Navigator.pushReplacement, and Navigator.pushAndRemoveUntil, and when would you genuinely reach for each individual one of these three particular methods? How can you properly intercept and correctly handle the physical Android back button using the PopScope widget, such as showing a confirmation dialog before genuinely actually allowing the user to leave a screen with unsaved changes? How should a large Flutter app properly structure its own overall routing architecture to genuinely scale well as the total number of individual screens grows into the dozens or even hundreds? How can you properly implement custom transition animations that genuinely differ meaningfully based on the specific type of navigation actually occurring, such as a genuinely different transition for forward navigation compared to backward navigation?
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Flutter › Navigation & Routing in Flutter

How do you properly implement a bottom navigation bar in Flutter, correctly switching between several genuinely separate main top level screens while properly preserving each individual tab's own current specific state?

Intermediate

Answer

Implementing a bottom navigation bar typically involves using a BottomNavigationBar widget together with an IndexedStack, which properly keeps every single one of your several genuinely separate tab screens genuinely alive simultaneously within memory while only actually visually displaying whichever one particular currently selected tab happens to be genuinely active, correctly preserving each individual tab's own current specific scroll position and internal state even as a user actually switches back and forth between them, rather than an approach that would otherwise completely rebuild a given tab's own screen entirely from scratch every single time it is genuinely selected again.
IndexedStack(
  index: currentTabIndex,
  children: [HomeTab(), SearchTab(), ProfileTab()],
)
Real-world example A shopping app uses IndexedStack together with a BottomNavigationBar to correctly preserve a user's own current scroll position within their search results tab, even after they briefly switch over to check their profile tab and then genuinely switch back again.

Common follow-ups: What genuinely happens to overall memory usage if you have a genuinely very large number of separate tabs, each containing quite heavy screens, all kept simultaneously alive together using IndexedStack?;What is the specific practical difference between using IndexedStack and simply rebuilding a genuinely brand new screen from scratch each single time a tab is selected?

Flutter Performance Optimization;Flutter Widgets Fundamentals (Stateless & Stateful)
All 7 Navigation & Routing in Flutter questions