如何在flutter应用中使用streambuilder中的链接导航？

dependencies:
  flutter_bloc: ^7.0.0
  flutter_bloc_navigation: ^1.0.0

import 'dart:async';
import 'package:flutter_bloc/flutter_bloc.dart';

class NavigationBloc extends Bloc<NavigationEvent, NavigationState> {
  NavigationBloc() : super(NavigationState.initial());

  @override
  Stream<NavigationState> mapEventToState(NavigationEvent event) async* {
    if (event is NavigateToPage1Event) {
      yield NavigationState.page1();
    } else if (event is NavigateToPage2Event) {
      yield NavigationState.page2();
    }
    // ... 添加其他导航事件处理逻辑
  }
}

abstract class NavigationEvent {}

class NavigateToPage1Event extends NavigationEvent {}

class NavigateToPage2Event extends NavigationEvent {}

class NavigationState {
  const NavigationState(this.pageIndex);

  final int pageIndex;

  factory NavigationState.initial() => NavigationState(0);

  factory NavigationState.page1() => NavigationState(1);

  factory NavigationState.page2() => NavigationState(2);
}

import 'package:flutter/material.dart';
import 'package:flutter_bloc/flutter_bloc.dart';
import 'navigation_bloc.dart';

class HomePage extends StatelessWidget {
  final NavigationBloc _navigationBloc = NavigationBloc();

  @override
  Widget build(BuildContext context) {
    return BlocProvider<NavigationBloc>(
      create: (context) => _navigationBloc,
      child: Scaffold(
        appBar: AppBar(
          title: Text('Flutter App'),
        ),
        body: Center(
          child: StreamBuilder<NavigationState>(
            stream: _navigationBloc.stream,
            builder: (context, snapshot) {
              if (snapshot.hasData) {
                final pageIndex = snapshot.data!.pageIndex;
                if (pageIndex == 0) {
                  return Page1();
                } else if (pageIndex == 1) {
                  return Page2();
                }
              }
              return Container();
            },
          ),
        ),
        bottomNavigationBar: BottomNavigationBar(
          items: [
            BottomNavigationBarItem(icon: Icon(Icons.home), label: 'Page 1'),
            BottomNavigationBarItem(icon: Icon(Icons.settings), label: 'Page 2'),
          ],
          onTap: (index) {
            if (index == 0) {
              _navigationBloc.add(NavigateToPage1Event());
            } else if (index == 1) {
              _navigationBloc.add(NavigateToPage2Event());
            }
          },
        ),
      ),
    );
  }
}

class Page1 extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return Center(
      child: Text('Page 1'),
    );
  }
}

class Page2 extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return Center(
      child: Text('Page 2'),
    );
  }
}