I'm trying to connect a `webview_flutter` `WebView` to a `BottomNavigationBar`.
I want the view to be reloaded with a new URL whenever a tab is tapped. In
the `onTap` callback I update the `_currentUrl` to a new url and call set state with the new tab index.

Why is the tab bar updating but the web view is not rebuilt?
What did I miss?

```
class WebViewApp extends StatefulWidget {
  @override
  State<StatefulWidget> createState() {
    return WebViewState();
  }
}

class WebViewState extends State<WebViewApp> {
  int _currentTabIndex = 0;
  String _currentUrl = URL.home;

  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      title: 'Flutter WebView Demo',
      home: Scaffold(
        body: WebView(initialUrl: _currentUrl),
        bottomNavigationBar: BottomNavigationBar(
          currentIndex: _currentTabIndex,
          items: [
            BottomNavigationBarItem(
              icon: Icon(Icons.home),
              title: Text('Home'),
            ),
            BottomNavigationBarItem(
              icon: Icon(Icons.search),
              title: Text('Search'),
            ),
            BottomNavigationBarItem(
              icon: Icon(Icons.calendar_today),
              title: Text('Profile'),
            ),
          ],
          onTap: (index) {
            switch (index) {
              case 0:
                _currentUrl = URL.home;
                break;
              case 1:
                _currentUrl = URL.search;
                break;
              case 2:
                _currentUrl = URL.calendar;
                break;
            }
            setState(() {
              _currentTabIndex = index;
            });
          },
        ),
      ),
    );
  }
}

```