Flutter 3.29版本优化了开发流程并提升了性能，对 Impeller、Cupertino、DevTools 等进行了更新。

CupertinoNavigationBar和CupertinoSliverNavigationBar现在接受底部小部件，通常是搜索字段或分段控件。

例如本小节内容就是放置了一个输入框（当然也是官方的Demo）：

class NavBarExample extends StatefulWidget {const NavBarExample({super.key});@overrideState<NavBarExample> createState() => _NavBarExampleState();
}class _NavBarExampleState extends State<NavBarExample> {@overrideWidget build(BuildContext context) {return CupertinoPageScaffold(navigationBar: const CupertinoNavigationBar(middle: Text('CupertinoNavigationBar Sample'),//核心在这里bottom: _NavigationBarSearchField(),automaticBackgroundVisibility: false,),child: Column(children: <Widget>[Container(height: 50, color: CupertinoColors.systemRed),Container(height: 50, color: CupertinoColors.systemGreen),Container(height: 50, color: CupertinoColors.systemBlue),Container(height: 50, color: CupertinoColors.systemYellow),],),);}
}

_NavigationBarSearchField 的定义如下：

class _NavigationBarSearchField extends StatelessWidgetimplements PreferredSizeWidget {const _NavigationBarSearchField();static const double padding = 8.0;static const double searchFieldHeight = 35.0;@overrideWidget build(BuildContext context) {return const Padding(padding: EdgeInsets.symmetric(horizontal: padding, vertical: padding),child: SizedBox(height: searchFieldHeight,child: CupertinoSearchTextField(),),);}@overrideSize get preferredSize =>const Size.fromHeight(searchFieldHeight + padding * 2);
}