title: Flutter: Nested routing with persistent BottomNavigationBar but without building the unselected pages unnecessarily
body: <p>Throughout the <a href="https://medium.com/coding-with-flutter/flutter-case-study-multiple-navigators-with-bottomnavigationbar-90eb6caa6dbf" rel="noreferrer">internet</a> and <a href="https://stackoverflow.com/questions/54767298/need-a-persistent-same-bottom-navigation-bar-for-all-screens-flutter">stackoverflow</a> I've searched and seen a lot of solutions to the problem of nested navigation with a persistent BottomNavigationBar for Flutter apps. Some of them using <em>Navigators</em> with <em>IndexedStack</em> or <em>PageView</em> and so on and so forth. All of them work just fine <strong>except</strong> that they will unnecessarily build the unselected tabs (sometimes even rebuilding all of them every time you switch tabs) thus making the solution not performatic. I did finally come up with a solution to that – as I was struggling with this problem myself.</p>