可以通过在NavigationView的页面中混合AutomaticKeepAliveClientMixin来保持页面状态。以下是示例代码：

import 'package:flutter/material.dart';
import 'package:fluent_ui/fluent_ui.dart';

class MyPage extends StatefulWidget {
  const MyPage({Key? key}) : super(key: key);

  @override
  _MyPageState createState() => _MyPageState();
}

class _MyPageState extends State with AutomaticKeepAliveClientMixin {
  @override
  bool get wantKeepAlive => true;

  @override
  Widget build(BuildContext context) {
    super.build(context); // 必须调用此方法才能保持状态

    return Scaffold(
      body: NavigationView(
        pane: NavigationPane(
          selected: 4,
          items: [
            PaneItem(
              icon: const Icon(FluentIcons.home_20_filled),
              title: const Text('Home'),
            ),
            ...
          ],
        ),
        content: Container(
          padding: const EdgeInsets.all(16),
          child: const Text('My Page Content'),
        ),
      ),
    );
  }
}

在这个示例中，MyPage被混合了AutomaticKeepAliveClientMixin，并重写了它的wantKeepAlive getter方法，返回true来指示页面的状态应该被保留。当你在NavigationView中导航到MyPage时，页面的状态将保持不变。为了使状态保持生效，你需要在State的build方法中调用super.build方法。