09 Flutter底部Tab切换保持页面状态的几种方法

阳光穿透心脏的1/2处 2023-08-17 15:58 149阅读 0赞

IndexedStack：保此所有页面的状态：

AutomaticKeepAliveClientMixin：保此部分页面的状态：

修改的页面代码：

页面效果：

![1057166-20190826113327106-1694147510.png][]

![1057166-20190826113340670-567814466.png][]

Tabs.dart

import 'package:flutter/material.dart';
    
    import 'Home.dart';
    import 'Cart.dart';
    import 'Category.dart';
    import 'User.dart';
    
    class Tabs extends StatefulWidget {
      Tabs({Key key}) : super(key: key);
    
      _TabsState createState() => _TabsState();
    }
    
    class _TabsState extends State<Tabs> {
      int _currentIndex = 1;
      PageController _pageController;
      void initState(){
        super.initState();
        this._pageController=new PageController(initialPage: this._currentIndex);
      }
      List<Widget> _pageList = [HomePage(), CategoryPage(), CartPage(), UserPage()];
      @override
      Widget build(BuildContext context) {
        return Container(
          child: Scaffold(
            appBar: AppBar(
              title: Text('jdshop'),
            ),
            //页面状态保持第一种方法：
            //保持所有的页面状态，使用indexedStack
            // body:IndexedStack(
            //   index: this._currentIndex,
            //   children:_pageList
            // ),
            //保持部分页面的状态：
            //
    
            body:PageView(  //修改的部分：
              controller: this._pageController,
              children:this._pageList,
              // onPageChanged(){
         
              // },
            ),
            bottomNavigationBar: BottomNavigationBar(
              currentIndex: this._currentIndex,
              onTap: (index) {
                this.setState(() {
                  this._currentIndex = index;
                   this._pageController.jumpToPage(this._currentIndex);
                });
              },
              type: BottomNavigationBarType.fixed,
              fixedColor: Colors.red,
              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.people), title: Text('我的'))
              ],
            ),
          ),
        );
      }
    }

Home.dart

import 'package:flutter/material.dart';
    
    
    //热门推荐：
    import '../../model/ProductModel.dart';
    import 'package:flutter_swiper/flutter_swiper.dart';
    // import 'dart:convert';
    import '../../services/ScreenAdaper.dart';
    import '../../config/Config.dart';
    import 'package:dio/dio.dart';
    //轮播图类模型：
    import '../../model/FocusModel.dart';
    
    
    
    class HomePage extends StatefulWidget {
      HomePage({Key key}) : super(key: key);
    
      _HomePageState createState() => _HomePageState();
    }
    
    class _HomePageState extends State<HomePage> with AutomaticKeepAliveClientMixin {
      //轮播图：
      //flutter run -d all 链接多个设备的命令：
      List _focusData = [];
      List _hotProductList=[];
      List _bestProductList=[];
        @override
      // TODO: implement wantKeepAlive
      bool get wantKeepAlive => true;
      void initState() {
        super.initState();
        _getFocusData();
        _getHotProductData();
        _getBestProductData();
      }
      //获取轮播图数据：
      _getFocusData() async {
        var api = '${Config.domain}api/focus';
        var result = await Dio().get(api);
        var focusList = FocusModel.fromJson(result.data);
        focusList.result.forEach((value) {
          print(value.title);
          print(value.pic);
        });
        setState(() {
          this._focusData = focusList.result;
        });
      }
      //获取猜你喜欢的数据：
      _getHotProductData() async{
        var api='${Config.domain}api/plist?is_hot=1';
        var result=await Dio().get(api);
        var hotProductList=ProductModel.fromJson(result.data);
        setState(() {
         this._hotProductList= hotProductList.result;
        });
      }
      //获取热门推荐的数据：
      _getBestProductData() async{
        var api='${Config.domain}api/plist?is_best=1';
        var result=await Dio().get(api);
        var bestProductList=ProductModel.fromJson(result.data);
        setState(() {
         this._bestProductList= bestProductList.result;
        });
      }
    
      Widget _swiperWidget() {
        // List<Map> imgList = [
        //   {"url": "https://www.itying.com/images/flutter/slide01.jpg"},
        //   {"url": "https://www.itying.com/images/flutter/slide02.jpg"},
        //   {"url": "https://www.itying.com/images/flutter/slide03.jpg"}
        // ];
        if (this._focusData.length > 0) {
          return Container(
            child: AspectRatio(
              aspectRatio: 2 / 1,
              child: Swiper(
                itemBuilder: (BuildContext context, int index) {
                  String pic=this._focusData[index].pic;
                  pic=Config.domain+pic.replaceAll('\\', '/');
                  return new Image.network(
                    "${pic}",
                    fit: BoxFit.fill,
                  );
                },
                itemCount: this._focusData.length,
                pagination: new SwiperPagination(),
                control: new SwiperControl(),
                autoplay: true,
              ),
            ),
          );
        } else {
          return Text('加载中~');
        }
      }
    
      //标题：
      Widget _titleWidget(value) {
        return Container(
          height: ScreenAdaper.height(46),
          margin: EdgeInsets.only(left: ScreenAdaper.width(20)),
          padding: EdgeInsets.only(left: ScreenAdaper.width(20)),
          decoration: BoxDecoration(
              border: Border(
                  left: BorderSide(
                      color: Colors.red, width: ScreenAdaper.width(10)))),
          child: Text(value, style: TextStyle(color: Colors.black54)),
        );
      }
    
      //热门商品：
      Widget _hotProductListWidget() {
        if(this._hotProductList.length>0){
        return Container(
          height: ScreenAdaper.height(240),
          padding: EdgeInsets.all(ScreenAdaper.width(20)),
          // width: double.infinity, //寬度自適應
          child: ListView.builder(
            scrollDirection: Axis.horizontal,
            itemBuilder: (contxt, index) {
    
              String sPic=this._hotProductList[index].sPic;
              sPic=Config.domain+sPic.replaceAll('\\', '/');
              return Column(
                children: <Widget>[
                  Container(
                    height: ScreenAdaper.height(140),
                    width: ScreenAdaper.width(140),
                    margin: EdgeInsets.only(right: ScreenAdaper.width(21)),
                    child: Image.network(
                       "${sPic}",
                      fit: BoxFit.cover),
                  ),
                  Container(
                    padding: EdgeInsets.only(top: ScreenAdaper.height(10)),
                    height: ScreenAdaper.height(44),
                    child: Text(
                      "￥${this._hotProductList[index].price}",
                      style: TextStyle(color: Colors.red),
                      ),
                  )
                ],
              );
            },
            itemCount: this._hotProductList.length,
          ),
        );
      
        }else{
          return Text('暂无热门推荐数据');
        }
    
      }
    
      Widget _recProductListWidget() {
    
    
        var itemWidth = (ScreenAdaper.getScreenWidth() - 30) / 2;
        return         Container(
              padding: EdgeInsets.all(10),
              child: Wrap(
                runSpacing: 10,
                spacing: 10,
                children:this._bestProductList.map((value){
                  //图片：
                  var sPic=value.sPic;
                  sPic=Config.domain+sPic.replaceAll('\\','/');
    
        return Container(
          padding: EdgeInsets.all(ScreenAdaper.width(20)),
          width: itemWidth,
          decoration:
          BoxDecoration(border: Border.all(color: Colors.black12, width: 1)),
          child: Column(
            children: <Widget>[
              Container(
                width: double.infinity,
                child: AspectRatio(
                  aspectRatio: 1 / 1,
                  child: Image.network(
                      "${sPic}",
                      fit: BoxFit.cover),
                ),
              ),
              Padding(
                padding: EdgeInsets.only(top: ScreenAdaper.height(10)),
                child: Text(
                  "${value.title}",
                  maxLines: 2,
                  overflow: TextOverflow.ellipsis,
                  style: TextStyle(color: Colors.black54),
                ),
              ),
              Padding(
                padding: EdgeInsets.only(top: ScreenAdaper.height(20)),
                child: Stack(
                  children: <Widget>[
                    Align(
                      alignment: Alignment.centerLeft,
                      child: Text(
                        "${value.price}",
                        style: TextStyle(color: Colors.red, fontSize: 16),
                      ),
                    ),
                    Align(
                      alignment: Alignment.centerRight,
                      child: Text(
                        "￥${value.oldPrice}",
                        style: TextStyle(
                            color: Colors.black54,
                            fontSize: 16,
                            decoration: TextDecoration.lineThrough),
                      ),
                    )
                  ],
                ),
              )
            ],
          ),
        );
     
    
    
    
                }).toList(),
              ),
            );
    
    
    
      }
    
      @override
      Widget build(BuildContext context) {
        ScreenAdaper.init(context);
        return ListView(
          children: <Widget>[
            _swiperWidget(),
            SizedBox(height: ScreenAdaper.height(20)),
            _titleWidget("猜你喜欢"),
            _hotProductListWidget(),
            SizedBox(height: ScreenAdaper.height(20)),
            _titleWidget("热门推荐"),
            _recProductListWidget()
          ],
        );
      }
    }

Category.dart

import 'package:flutter/material.dart';
    import '../../services/ScreenAdaper.dart';
    import '../../config/Config.dart';
    import 'package:dio/dio.dart';
    import '../../model/CateModel.dart';
    
    class CategoryPage extends StatefulWidget {
      CategoryPage({Key key}) : super(key: key);
    
      _CategoryPageState createState() => _CategoryPageState();
    }
    
    class _CategoryPageState extends State<CategoryPage>  with AutomaticKeepAliveClientMixin{
      int _selectIndex = 0;
      List _leftCateList = [];
      List _rightCateList = [];
          @override
      // TODO: implement wantKeepAlive
      bool get wantKeepAlive => true;
      @override
      void initState() {
        super.initState();
        _getLeftCateData();
      }
    
      //左侧数据：
      _getLeftCateData() async {
        var api = '${Config.domain}api/pcate';
        var result = await Dio().get(api);
        var leftCateList = CateModel.fromJson(result.data);
        setState(() {
          this._leftCateList = leftCateList.result;
        });
        _getRightCateData(leftCateList.result[0].sId);
      }
    
      //右侧数据：
      _getRightCateData(pid) async {
        var api = '${Config.domain}api/pcate?pid=${pid}';
        var result = await Dio().get(api);
        var rightCateList = CateModel.fromJson(result.data);
        setState(() {
          this._rightCateList = rightCateList.result;
        });
      }
    
      //左侧组件
      Widget _leftCateWidget(leftWidth) {
        if (this._leftCateList.length > 0) {
          return Container(
            width: leftWidth,
            height: double.infinity,
            // color: Colors.red,
            child: ListView.builder(
              itemCount: this._leftCateList.length,
              itemBuilder: (context, index) {
                return Column(
                  children: <Widget>[
                    InkWell(
                      onTap: () {
                        setState(() {
                          // setState(() {
                          _selectIndex = index;
                           this._getRightCateData(this._leftCateList[index].sId);
                        });
                      },
                      child: Container(
                        width: double.infinity,
                        height: ScreenAdaper.height(56),
                        padding: EdgeInsets.only(top: ScreenAdaper.height(24)),
                        child: Text("${this._leftCateList[index].title}",
                            textAlign: TextAlign.center),
                        color: _selectIndex == index
                            ? Color.fromRGBO(240, 246, 246, 0.9)
                            : Colors.white,
                      ),
                    ),
                    Divider(height: 1),
                  ],
                );
              },
            ),
          );
        } else {
          return Container(
            width: leftWidth,
            height: double.infinity,
          );
        }
      }
    
      //右侧组件：
      Widget _rightCateWidget(rightItemWidth, rightItemHeigth) {
        if (this._rightCateList.length > 0) {
          return Expanded(
            flex: 1,
            child: Container(
              padding: EdgeInsets.all(10),
              height: double.infinity,
              color: Color.fromRGBO(240, 246, 246, 0.9),
              // color: Colors.blue,
              child: GridView.builder(
                gridDelegate: SliverGridDelegateWithFixedCrossAxisCount(
                    crossAxisCount: 3,
                    childAspectRatio: rightItemWidth / rightItemHeigth,
                    crossAxisSpacing: 10,
                    mainAxisSpacing: 10),
                itemCount: this._rightCateList.length,
                itemBuilder: (context, index) {
                  //处理图片：
                  String pic=this._rightCateList[index].pic;
                  pic=Config.domain+pic.replaceAll('\\','/');
                  return Container(
                    // padding: EdgeInsets.all(ScreenAdaper.width(20)),
                    child: Column(
                      children: <Widget>[
                        AspectRatio(
                          aspectRatio: 1 / 1,
                          child: Image.network(
                              "${pic}",
                              fit: BoxFit.cover),
                        ),
                        Container(
                          height: ScreenAdaper.height(32),
                          child: Text("${this._rightCateList[index].title}"),
                        )
                      ],
                    ),
                  );
                },
              ),
            ),
          );
        } else {
          return Expanded(
              flex: 1,
              child: Container(
                padding: EdgeInsets.all(10),
                height: double.infinity,
                color: Color.fromRGBO(240, 246, 246, 0.9),
                child: Text('加载中...'),
              ));
        }
      }
    
      Widget build(BuildContext context) {
        ScreenAdaper.init(context);
    
        //计算右侧GridView宽高比：
        var leftWidth = ScreenAdaper.getScreenWidth() / 4;
        //右侧宽高=总宽度-左侧宽度-Gridview外层元素左右的Padding值-GridView中间的间距
        var rightItemWidth =
            (ScreenAdaper.getScreenWidth() - leftWidth - 20 - 20) / 3;
        rightItemWidth = ScreenAdaper.width(rightItemWidth);
        var rightItemHeigth = rightItemWidth + ScreenAdaper.height(32);
    
        return Row(
          children: <Widget>[
            _leftCateWidget(leftWidth),
            _rightCateWidget(rightItemWidth, rightItemHeigth)
          ],
        );
      }
    }

转载于:https://www.cnblogs.com/yiweiyihang/p/11410269.html

[1057166-20190826113327106-1694147510.png]: /images/20230810/bc3574228045467f98eb4a4e9ce78bea.png
[1057166-20190826113340670-567814466.png]: /images/20230810/e3dc9390a0d24a0fa869ac138f1d2da0.png