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布吉网站的建设,免费建设个人网站,网络营销推广岗位,公司网站域名注册费用可以用ScrollController组件来实现这样列表上拉加载更多的功能: 1. 定义变量在StatefulWidget 的组件内，添加三个属性： // 滚动视图的控制器final ScrollController _scrollController ScrollController();// 是否已显示了上拉加载中bool _isShowM…

可以用ScrollController组件来实现这样列表上拉加载更多的功能:
请添加图片描述

1. 定义变量

在StatefulWidget 的组件内，添加三个属性：

// 滚动视图的控制器final ScrollController _scrollController = ScrollController();// 是否已显示了上拉加载中bool _isShowMore = false;// 是否有更多的数据bool _isHaveMoreData = true;

2. 在初始化的方法中，添加对`ScrollController`的监听

重写initState的方法，并在initState方法中，添加ScrollController的监听，代码如下：

@overridevoid initState() {super.initState();// 对 _scrollController 添加监听_scrollController.addListener((){// 内容视图最大的高度double maxScrollExtent = _scrollController.position.maxScrollExtent;// 视图滚动的大小double scrollContentOffY = _scrollController.position.pixels;if (scrollContentOffY > maxScrollExtent + Screenadapter.height(40)) {// 超出了内容视图高度的20，就重新上拉加载更多if (_isShowMore == false && _isHaveMoreData == true) {// 未显示, print("上拉加载更多");// 添加网络请求_getProductListDataRequest();}}});

3. 在`ListView`中，关联`ScrollController`

代码如下：

ListView.builder(// 关联 ScrollControllercontroller: _scrollController,itemBuilder: (BuildContext context, int index) {return Column();}
)

4. 写一个简易的`Loading`的加载视图

代码如下：

import 'package:fangjd/Services/ScreenAdapter.dart';
import 'package:flutter/material.dart';class Loadingwidget extends StatelessWidget {const Loadingwidget({super.key});@overrideWidget build(BuildContext context) {return Center(child: Container(padding: EdgeInsets.all(Screenadapter.width(20)),child: Row(mainAxisAlignment: MainAxisAlignment.center,children: [CircularProgressIndicator(strokeWidth: 1.0),SizedBox(width: Screenadapter.width(20)),Text("加载中....")],),),);}
}

5. 在列表的底部视图，添加`加载中`的视图或者添加`我是我底线`的视图

代码如下：

// 商品列表底部的视图Widget _productBottomWiget(int index) {if (_isHaveMoreData == true) {// 如果有更多的数据，上拉，就显示“加载中”， 其中_productList 是数据源if (_isShowMore && (index == _productList.length -1)) {// 只有最后一个数据，才添加 “加载中”的loading视图return Loadingwidget();} else {// 其他数据 就什么都不显示return SizedBox(height: 1);}} else {// 如果没有更多的数据，if (index == _productList.length -1) {// 在最后一个数据，添加 “--我也是有底线的--”的视图return Padding(padding:EdgeInsets.only(top: Screenadapter.height(30)), child: Text("--我也是有底线的--", textAlign: TextAlign.center,));} else {// 其他数据 就什么都不显示return SizedBox(height: 1);}}}

6. 模拟网络数据的请求

代码如下:

// -----网络请求--------void _getProductListDataRequest() async {setState(() {// 当调用网络请求的时候，设置_isShowMore 为 true， 表示需要展示“加载中”的底部视图_isShowMore = true;});// 模拟网络延迟await Future.delayed(Duration(seconds: 2)); List<ProductItemModel> mockDataList = _mockData();setState(() {_productList.addAll(mockDataList);// 等网路请求成功后，设置 _isShowMore 为 false， 表示 隐藏 “加载中”的底部视图_isShowMore = false;if (_productList.length > 20) {// 模拟没有更多数据了，就展示“我是有底线的”的视图 _isHaveMoreData = false;}});}// 模拟数据List<ProductItemModel> _mockData() {// returnList<ProductItemModel> mockList = [];for (var index in [1,2,3,4,5,6,7,8,9,0]) {var model = ProductItemModel(iId: 1, title: '笔记本电脑$index', price: "￥3980", oldPrice: "￥4999", pic: "https://www.itying.com/images/flutter/hot${index+1}.jpg");mockList.add(model);}return mockList;}

7. 完整的代码实例

import 'package:fangjd/CommonWidget/LoadingWidget.dart';
import 'package:fangjd/Models/ProductModel.dart';
import 'package:fangjd/Services/ScreenAdapter.dart';
import 'package:flutter/material.dart';class ProductlistPage extends StatefulWidget {const ProductlistPage({super.key});@overrideState<ProductlistPage> createState() => _ProductlistPageState();
}class _ProductlistPageState extends State<ProductlistPage> {// ScaffoldState, 控制侧边栏的显示final GlobalKey<ScaffoldState> _scaffoldKey = GlobalKey<ScaffoldState>();// 筛选导航栏的索引int _selectIndex = 1;// 商品列表的数据List<ProductItemModel> _productList = [];// 滚动视图的控制器final ScrollController _scrollController = ScrollController();// 是否已显示了上拉加载中bool _isShowMore = false;// 是否有更多的数据bool _isHaveMoreData = true;@overridevoid initState() {super.initState();_scrollController.addListener((){// 内容视图最大的高度double maxScrollExtent = _scrollController.position.maxScrollExtent;// 视图滚动的大小double scrollContentOffY = _scrollController.position.pixels;if (scrollContentOffY > maxScrollExtent + Screenadapter.height(40)) {// 超出了内容视图高度的20，就重新上拉加载更多if (_isShowMore == false && _isHaveMoreData == true) {// 未显示_getProductListDataRequest();}}});// -----网络请求--------_getProductListDataRequest();}// -----网络请求--------void _getProductListDataRequest() async {setState(() {_isShowMore = true;});// 模拟网络延迟await Future.delayed(Duration(seconds: 2)); List<ProductItemModel> mockDataList = _mockData();setState(() {_productList.addAll(mockDataList);_isShowMore = false;if (_productList.length > 20) {_isHaveMoreData = false;}});}// 模拟数据List<ProductItemModel> _mockData() {// returnList<ProductItemModel> mockList = [];for (var index in [1,2,3,4,5,6,7,8,9,0]) {var model = ProductItemModel(iId: 1, title: '笔记本电脑$index', price: "￥3980", oldPrice: "￥4999", pic: "https://www.itying.com/images/flutter/hot${index+1}.jpg");mockList.add(model);}return mockList;}// -----视图设置--------// 设置 筛选透视图的底部选中的线Border _selectHeaderBoder() {return Border(bottom: BorderSide(width: 1,color: Colors.red));}// 筛选导航栏Widget _subHeaderWidget() {return Positioned(top: 0.0,child: Container(height: Screenadapter.height(80),width: Screenadapter.screenWidth(),decoration: BoxDecoration(border: Border(bottom: BorderSide(width: 1,color: Colors.black12),),),child: Row(children: [Expanded(child: InkWell(onTap: () {setState(() {_selectIndex = 1;});},child: Container(decoration: BoxDecoration(border: _selectIndex == 1 ? _selectHeaderBoder() : null),child: Center(child: Text("综合", style: TextStyle(color: _selectIndex == 1 ? Colors.red : Colors.black))),),)),Expanded(child: InkWell(onTap: () {setState(() {_selectIndex = 2;});},child: Container(decoration: BoxDecoration(border: _selectIndex == 2 ? _selectHeaderBoder() : null),child: Center(child: Text("销量", style: TextStyle(color: _selectIndex == 2 ? Colors.red : Colors.black))),),)),Expanded(child: InkWell(onTap: () {setState(() {_selectIndex = 3;});},child: Container(decoration: BoxDecoration(border: _selectIndex == 3 ? _selectHeaderBoder() : null),child: Center(child: Text("价格", style: TextStyle(color: _selectIndex == 3 ? Colors.red : Colors.black))),),)),Expanded(child: InkWell(onTap: () {setState(() {_selectIndex = 4;});_scaffoldKey.currentState?.openEndDrawer();},child: Container(decoration: BoxDecoration(border: _selectIndex == 4 ? _selectHeaderBoder() : null),child: Center(child: Text("筛选", style: TextStyle(color: _selectIndex == 4 ? Colors.red : Colors.black))),),)),],),));}// 商品列表底部的视图Widget _productBottomWiget(int index) {if (_isHaveMoreData == true) {if (_isShowMore && (index == _productList.length -1)) {return Loadingwidget();} else {return Text("");}} else {if (index == _productList.length -1) {return Padding(padding:EdgeInsets.only(top: Screenadapter.height(30)), child: Text("--我也是有底线的--", textAlign: TextAlign.center,));} else {return SizedBox(height: 1);}}}// 商品列表Widget _productListWidget() {if (_productList.isNotEmpty) {return  Container(padding: EdgeInsets.all(Screenadapter.width(10)),margin: EdgeInsets.only(top: Screenadapter.height(80)),child: ListView.builder(controller: _scrollController,itemBuilder: (BuildContext context, int index) {ProductItemModel itemModel = _productList[index];return Column(children: [Row(children: [Container(padding: EdgeInsets.all(Screenadapter.width(20)),width: Screenadapter.width(220),height: Screenadapter.height(220),child: AspectRatio(aspectRatio: 1,child: Image.network(itemModel.pic, fit: BoxFit.cover)),),Expanded(child: Container(height: Screenadapter.height(220),padding: EdgeInsets.only(top: Screenadapter.height(10)),child: Column(mainAxisAlignment: MainAxisAlignment.start,crossAxisAlignment: CrossAxisAlignment.start,children: [Text(itemModel.title,maxLines: 2,overflow: TextOverflow.ellipsis,),SizedBox(height: Screenadapter.height(20)),Container(height: Screenadapter.height(36),width: double.infinity,child: Row(children: [Container(height: Screenadapter.height(40),width: Screenadapter.width(80),decoration: BoxDecoration(borderRadius: BorderRadius.circular(Screenadapter.height(18)),color: Colors.black12),child: Center(child: Text(' 4G ', style: TextStyle(color: Colors.black87))),),SizedBox(width: Screenadapter.width(20)),Container(height: Screenadapter.height(40),width: Screenadapter.width(80),decoration: BoxDecoration(borderRadius: BorderRadius.circular(Screenadapter.height(18)),color: Colors.black12),child: Center(child: Text(' 126 ', style: TextStyle(color: Colors.black87))),),],),),SizedBox(height: Screenadapter.width(20)),Text(itemModel.price, style: TextStyle(color: Colors.red, fontSize: 18))])))],),Divider(height: Screenadapter.height(2)),// 添加列表底部视图：显示“加载中”还是显示“我是有底线的”_productBottomWiget(index)],);},itemCount: _productList.length),);} else {return Loadingwidget();}}@overrideWidget build(BuildContext context) {return Scaffold(key: _scaffoldKey,appBar: AppBar(title: Text("商品分类"),actions: [// 去掉’endDrawer‘默认设置的图标Text("")],),endDrawer: Drawer(child: Center(child: Text("我是侧边栏")),),body: Stack(children: [// 筛选导航栏_subHeaderWidget(),// 商品列表_productListWidget()],),);}
}