EBook：底部导航栏全局跳转

想要在任意页面跳转到指定的底部导航栏，需要用到Provider。

将下标存放到 Provider 中，
将page 和 BottomNavigationBar的 index 绑定Provider.of(context).currentIndex，
在onTap(index)方法中使用Provider.of(context).currentIndex = index实现点击底部导航栏切换。
在其他页面使用Provider.of(context).currentIndex = 1，跳转到指定页面。

需要的插件如下：

flutter pub add provider

BottomNavigationBarProvider

bottom_nav_provider.dart

import 'package:flutter/material.dart';

class BottomNavProvider with ChangeNotifier {
  int _currentIndex = 0;

  int get currentIndex => _currentIndex;

  set currentIndex(int currentIndex) {
    _currentIndex = currentIndex;
    notifyListeners();
  }

  void setIndex(int index) {
    currentIndex = index;
  }
}

在main.dart中添加providers

main.dart

import 'package:e_book_clone/app.dart';
import 'package:e_book_clone/pages/bottom_nav_provider.dart';
import 'package:e_book_clone/theme/theme_provider.dart';
import 'package:flutter/material.dart';
import 'package:provider/provider.dart';

void main() {
  runApp(
    MultiProvider(providers: [
      // 主题
      ChangeNotifierProvider(create: (context) => ThemeProvider()),
	  // BottomNavigationBar  
      ChangeNotifierProvider(create: (context) => BottomNavProvider()),
    ], child: const MyAPP()),
  );
}

RootPage

import 'package:e_book_clone/json/root_app_json.dart';
import 'package:e_book_clone/pages/douban_read/douban_read_page.dart';
import 'package:e_book_clone/pages/home/home_page.dart';
import 'package:e_book_clone/pages/my_book/my_book_page.dart';
import 'package:e_book_clone/pages/ebook_store/store_page.dart';
import 'package:e_book_clone/pages/bottom_nav_provider.dart';
import 'package:flutter/material.dart';
import 'package:flutter_lazy_indexed_stack/flutter_lazy_indexed_stack.dart';
import 'package:provider/provider.dart';
import 'package:salomon_bottom_bar/salomon_bottom_bar.dart';

class RootPage extends StatelessWidget {
  const RootPage({super.key});

  @override
  Widget build(BuildContext context) {
    var bg = Theme.of(context).colorScheme.surface;
    return Scaffold(
      appBar: AppBar(
          elevation: 0,
          toolbarHeight: 0,
          backgroundColor: bg,
          surfaceTintColor: bg),
      backgroundColor: bg,
      bottomNavigationBar: _getBottomNavigator(context),
      body: LazyIndexedStack(
        index: Provider.of<BottomNavProvider>(context).currentIndex,
        children: const [
          HomePage(),
          DoubanReadPage(),
          StorePage(),
          MyBookPage(),
        ],
      ),
    );
  }


  Widget _getBottomNavigator(BuildContext context) {
    return SalomonBottomBar(
      currentIndex: Provider.of<BottomNavProvider>(context).currentIndex,
      onTap: (index) {
        // setState(() {
        //   pageIndex = index;
        // });
        Provider.of<BottomNavProvider>(context, listen: false).currentIndex =
            index;
      },
      items: List.generate(
        rootAppJson.length,
        (index) {
          return SalomonBottomBarItem(
            selectedColor: Theme.of(context).colorScheme.onSurface,
            unselectedColor: Theme.of(context).colorScheme.inversePrimary,
            icon: Icon(rootAppJson[index]['icon']),
            title: Text(rootAppJson[index]['text']),
          );
        },
      ),
    );
  }
}