AutomaticKeepAliveClientMixin保持页面状态

import 'package:flutter/material.dart';

import 'tabs/Cart.dart';
import 'tabs/Category.dart';
import 'tabs/Home.dart';
import 'tabs/User.dart';

class TabsPage extends StatefulWidget {
  TabsPage({Key key}) : super(key: key);

  @override
  _TabsPageState createState() {
    return _TabsPageState();
  }
}

class _TabsPageState extends State<TabsPage> {
  int _indexPageCount = 0;
  PageController _pageController;

  @override
  void initState() {
    super.initState();
    _pageController = new PageController(initialPage: _indexPageCount);
  }

  @override
  void dispose() {
    super.dispose();
  }

  List<Widget> pageList = [HomePage(), CategoryPage(), CartPage(), UserPage()];

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(title: Text("在线商城"),),
      body: PageView(
        controller: _pageController,
        children: pageList,
      ),
      bottomNavigationBar: BottomNavigationBar(
        type: BottomNavigationBarType.fixed,
        items: [
          BottomNavigationBarItem(icon: Icon(Icons.home), title: Text("首页")),
          BottomNavigationBarItem(icon: Icon(Icons.category), title: Text("分类")),
          BottomNavigationBarItem(icon: Icon(Icons.shopping_cart), title: Text("购物车")),
          BottomNavigationBarItem(icon: Icon(Icons.person), title: Text("个人")),
        ],
        currentIndex :_indexPageCount,
        onTap: (index) {
          setState(() {
            _indexPageCount = index;
            _pageController.jumpToPage(index);
          });
        },
      ),
    );
  }
}

在需要页面的类上with  AutomaticKeepAliveClientMixin 并实现

@override
bool get wantKeepAlive => true;