有图有真相：

想要实现一个面包屑导航栏需要考虑一下问题：

1，实现一个面包屑导航栏的效果并不难

2，面包屑下方的页面状态如何维护

3，导航栏和下方页面如何实现数据同步

这里说一下本人的愚见，大佬们有其他思路可以在评论区留言，大家相互学习：
1，导航栏界面，我直接用一个Row布局生成的
2，首先面包屑下方的页面状态可以使用Navigator进行维护，这样省去了好多处理路由的问题，并配置GlobalKey，用来在任何位置都能找到自己的Navigator；这里用到的Navigator和MaterialAPP 中的不是一个，需要注意；
3,数据同步，使用Provider；

下面直接看完整源码：

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

/// 创建日期: 2020/8/25
/// 作者: lijianbin
/// 描述:

///使用Navigator和Provider实现面包屑导航按钮
class BlockWidget extends StatelessWidget {
  final String title;

  const BlockWidget({Key key, this.title}) : super(key: key);

  @override
  Widget build(BuildContext context) {
    return Row(
      mainAxisSize: MainAxisSize.min,
      children: [Text(title), Icon(Icons.keyboard_arrow_right)],
    );
  }
}

///路由页面
class NavigatorPage extends StatefulWidget {
  final String title;
  final Widget child;

  const NavigatorPage({Key key, this.title, this.child}) : super(key: key);

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

class _NavigatorPageState extends State<NavigatorPage> {
  @override
  Widget build(BuildContext context) {
    return widget.child;
  }
}

///路由控制器
class NavigatorController with ChangeNotifier {
  List<NavigatorPage> _history = List();

  List<NavigatorPage> get history => _history;

  get size => _history.length;

  ///入栈
  void push(NavigatorPage page) {
    NavigatorState navigator = navigatorKey.currentState;
    navigator.push(MaterialPageRoute(builder: (context) {
      return page;
    }));
    _history.add(page);
    notifyListeners();
  }

  ///出栈
  void pop() {
    NavigatorState navigator = navigatorKey.currentState;
    if (navigator.canPop()) {
      navigator.pop();
      _history.removeLast();
      notifyListeners();
    }
  }

  ///出栈到指定索引
  void popUntil(int index) {
    while (size > index) {
      pop();
    }
  }
}

final GlobalKey<NavigatorState> navigatorKey = GlobalKey();

///路由导航器首页
class NavigatorHomeWidget extends StatelessWidget {
  final NavigatorPage home;

  const NavigatorHomeWidget({Key key, this.home}) : super(key: key);

  @override
  Widget build(BuildContext context) {
    return ChangeNotifierProvider.value(
      value: NavigatorController(),
      child: Column(
        children: [
          Container(
            alignment: Alignment.centerLeft,
            color: Colors.white,
            width: double.infinity,
            child: Consumer<NavigatorController>(
              builder: (context, NavigatorController data, child) {
                List<NavigatorPage> pages = List();
                pages.add(home);
                pages.addAll(data.history);

                List<GestureDetector> blocks = List();
                for (int i = 0; i < pages.length; i++) {
                  blocks.add(
                    GestureDetector(
                      onTap: () {
                        data.popUntil(i);
                      },
                      child: BlockWidget(title: pages[i].title),
                    ),
                  );
                }
                return SingleChildScrollView(
                  reverse: true,
                  scrollDirection: Axis.horizontal,
                  child: Row(
                    children: blocks,
                  ),
                );
              },
            ),
          ),
          Expanded(
            child: Builder(
              builder: (context) {
                return Navigator(
                  key: navigatorKey,
                  initialRoute: '/',
                  onGenerateRoute: (settings) {
                    WidgetBuilder builder;
                    switch (settings.name) {
                      case '/':
                        builder = (context) => home;
                        break;
                    }
                    return MaterialPageRoute(
                        builder: builder, settings: settings);
                  },
                );
              },
            ),
          ),
        ],
      ),
    );
  }
}

demo中的引用：

void main() {
  runApp(MaterialApp(
    home: Scaffold(
        appBar: AppBar(
          title: Text('面包屑导航'),
        ),
        body: HomePage()),
  ));
}

class HomePage extends StatefulWidget {
  @override
  _HomePageState createState() => _HomePageState();
}

class _HomePageState extends State<HomePage> {
  List<NavigatorPage> history = List();

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      body: Container(
        color: Colors.grey,
        child: Center(
          child: Container(
            height: 500,
            child: NavigatorHomeWidget(
              home: NavigatorPage(
                title: "首页",
                child: PA(
                  title: '首页',
                ),
              ),
            ),
          ),
        ),
      ),
    );
  }
}

class PA extends StatefulWidget {
  final title;

  const PA({Key key, this.title}) : super(key: key);

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

var index = 0;

class _PAState extends State<PA> {
  @override
  Widget build(BuildContext context) {
    return Container(
      color: Colors.greenAccent,
      child: Column(
        children: [
          RaisedButton(
            child: Text('push'),
            onPressed: () {
              Provider.of<NavigatorController>(context, listen: false).push(
                NavigatorPage(
                  title: "page:${++index}",
                  child: PA(
                    title: '${index}',
                  ),
                ),
              );
            },
          ),
          RaisedButton(
              child: Text('pop'),
              onPressed: () {
                Provider.of<NavigatorController>(context, listen: false).pop();
              }),
          Container(
            child: Text('当前页:${widget.title}'),
          ),
        ],
      ),
    );
  }
}