Flutter模板方法模式在多Tab列表中的应用 项目背景与需求在Flutter开发中，我们经常遇到需要实现多Tab栏列表的场景，每个Tab具有相似的结构（下拉刷新、上拉加载、列表展示），但数据类型和UI展示各不相同。本文将介绍如何使用模板方法模式来优雅地解决这个问题。模板方法模式简介模板方法模式是一种行为设计模式，它在超类中定义了一个算法的框架，允许子类在不修改结构的情况下重写特定步骤。在我们的场景中，每个Tab的加载流程（初始化→刷新→加载更多）是相同的，但具体的数据加载和UI展示是不同的。代码实现解析1. 抽象基类定义const int defaultPageSize = 10; abstract class TabData<T> { final String name; // tab名称 int total; // 数据数量 bool isSelected; // 选中状态 bool hasMore; // 是否有更多数据 List<T> items; // 数据列表 bool _isInited = false; // 是否初始化完成 final RefreshController controller; final Widget Function(BuildContext context,T item) itemBuilder; TabData({ required this.name, required this.itemBuilder, this.total = 0, this.isSelected = false, this.hasMore = true, this.items = const [] }) : controller = RefreshController(); int get pageSize => defaultPageSize; Future<List<T>> loadData(int page); void updateItems(List<T> newItems, bool isRefresh); Future<bool> init() async{ if (_isInited) { return true; } _isInited = true; await onRefresh(); return false; } Future<void> onRefresh() async { try { final data = await loadData(1); updateItems(data, true); hasMore = data.length >= pageSize; controller.refreshCompleted(); } catch (e) { controller.refreshFailed(); rethrow; } } Future<void> onLoadMore() async { if (!hasMore) { controller.loadNoData(); return; } try { final currentPage = (items.length / pageSize).ceil() + 1; final data = await loadData(currentPage); updateItems(data, false); hasMore = data.length >= pageSize; controller.loadComplete(); } catch (e) { controller.refreshFailed(); rethrow; } } void dispose() { controller.dispose(); } }设计要点：定义了完整的生命周期方法（init、onRefresh、onLoadMore）使用泛型T支持不同的数据类型封装了刷新控制器和分页逻辑提供itemBuilder回调实现UI定制化2. 具体子类实现点赞Tab实现：class LikeTabData extends TabData<LikeTabDataEntity>{ LikeTabData():super(name: "点赞",itemBuilder: (context,item){ return Text(item.name); }); @override Future<List<LikeTabDataEntity>> loadData(int page) async{ await Future.delayed(const Duration(seconds: 1)); return List.generate(pageSize, (index)=> LikeTabDataEntity(name: "$name 数据 ${page * pageSize + index}")); } @override void updateItems(List<LikeTabDataEntity> newItems, bool isRefresh) { items = isRefresh ? newItems : [...items, ...newItems]; total = items.length; } }评论Tab实现：class CommentTabData extends TabData<CommentTabDataEntity>{ CommentTabData():super(name: "评论",itemBuilder: (context,item) { Widget text () => Text(item.text,style: const TextStyle(color: Colors.white)); return Container( margin: const EdgeInsets.all(8), padding: const EdgeInsets.all(10), decoration: BoxDecoration( color: Colors.blueAccent, borderRadius: BorderRadius.circular(8), ), child: text(), ); }); @override Future<List<CommentTabDataEntity>> loadData(int page) async{ await Future.delayed(const Duration(seconds: 1)); return List.generate(pageSize, (index)=> CommentTabDataEntity(text: "$name 数据 ${page * pageSize + index}")); } @override void updateItems(List<CommentTabDataEntity> newItems, bool isRefresh) { items = isRefresh ? newItems : [...items, ...newItems]; total = items.length; } }子类只需实现：loadData：具体的数据加载逻辑updateItems：数据合并策略itemBuilder：列表项UI构建3. 状态管理class DialogState extends BaseViewState { List<TabData> tabDataList = [ LikeTabData(), CommentTabData(), LikeTabData(), CommentTabData(), ]; }4. 逻辑控制器class DialogLogic extends BaseGetXLifeCycleController{ late final PageController tabController; final state = DialogState(); @override void onInit() { super.onInit(); tabController = PageController(); state.viewState = TYPE_LOAD; update(); state.tabDataList.first.init().then((_)=> update()); Future.delayed(const Duration(seconds: 1),(){ state.tabDataList.first.isSelected = true; state.viewState = TYPE_NORMAL; update(); }); } @override void onClose() { tabController.dispose(); for(final item in state.tabDataList) { item.dispose(); } super.onClose(); } void onTabChange(int index) async{ for(int i = 0; i < state.tabDataList.length; i++) { state.tabDataList[i].isSelected = index == i; } update(); final isInited = await state.tabDataList[index].init(); if(!isInited) update(); } void changeTab(int index,BuildContext context){ final screenWidth = MediaQuery.of(context).size.width; tabController.animateTo(index * screenWidth,duration: const Duration(milliseconds: 300), curve: Curves.easeInOut); } void onRefresh(Future<void> Function() refresh) async{ await refresh(); update(); } void onLoadMore(Future<void> Function() loadMore) async{ await loadMore(); update(); } }5. UI界面实现class Dialog extends BaseTitleBottomSheet with GetXControllerMixin<DialogLogic>{ Dialog({super.key}); final logic = Get.put(DialogLogic()); final state = Get.find<DialogLogic>().state; @override String getTitle() => "Dialog"; @override Widget buildContent() { return buildPartBaseView( state.viewState,context, _buildContentWidget() ); } Widget _buildContentWidget() { return Expanded( child: Column( children: [ SingleChildScrollView( child: Row( mainAxisAlignment: MainAxisAlignment.spaceEvenly, children: [ for(int i = 0;i<state.tabDataList.length;i++) GestureDetector(onTap: ()=> logic.changeTab(i,context),child: _buildTabWidget(state.tabDataList[i])) ], ), ), Expanded( child: PageView.builder( controller: logic.tabController, onPageChanged: logic.onTabChange, itemCount: state.tabDataList.length, itemBuilder: (_,index){ final data = state.tabDataList[index]; if(data.items.isEmpty){ return const Center(child: Text("无数据"),); } return _KeepAliveList( data, keepAlive: true, onLoading: ()=> logic.onLoadMore(data.onLoadMore), onRefresh: ()=> logic.onRefresh(data.onRefresh), controller: data.controller ); }, ), ), ], ), ); } Widget _buildTabWidget(TabData entity){ final noSelectedStyle = TextStyle(color: Colors.black,fontSize: 23.w); final selectedStyle = TextStyle(color: Colors.blueAccent,fontSize: 23.w); final style = entity.isSelected ? selectedStyle : noSelectedStyle; return Row( mainAxisSize: MainAxisSize.min, children: [ Text(entity.name,style: style), Text("（${entity.total}）",style: style), ], ); } } class _KeepAliveList extends StatefulWidget { final TabData tabData; final bool keepAlive; final VoidCallback? onRefresh; final VoidCallback? onLoading; final RefreshController controller; const _KeepAliveList(this.tabData,{super.key,this.keepAlive = true,required this.controller,this.onRefresh,this.onLoading}); @override State<_KeepAliveList> createState() => _KeepAliveListState(); } class _KeepAliveListState extends State<_KeepAliveList> with AutomaticKeepAliveClientMixin{ @override Widget build(BuildContext context) { super.build(context); return SmartRefresher( controller: widget.controller, enablePullDown: true, enablePullUp: true, header: const ClassicHeader(), onRefresh: widget.onRefresh, onLoading: widget.onLoading, child: ListView.builder( itemCount: widget.tabData.items.length, itemBuilder: (context,index){ // 新版本dart可以使用switch匹配模式，可以穷举完全部密封类的子类 // 为了兼容只能使用if了 final tabData = widget.tabData; if(tabData is LikeTabData){ return tabData.itemBuilder(context,tabData.items[index]); }else if(tabData is CommentTabData){ return tabData.itemBuilder(context,tabData.items[index]); } throw "未知的TabData类型"; }, ), ); } @override bool get wantKeepAlive => widget.keepAlive; }设计优势1. 代码复用性公共的刷新、加载、分页逻辑在基类中实现新增Tab只需继承TabData并实现三个抽象方法2. 可维护性算法框架稳定，修改基类即可影响所有子类业务逻辑与UI展示分离3. 扩展性支持任意类型的列表数据可轻松添加新的Tab类型4. 一致性所有Tab保持相同的交互逻辑统一的错误处理和加载状态使用建议添加新Tab：只需创建新的TabData子类，实现loadData、updateItems和itemBuilder修改公共逻辑：在TabData基类中修改，所有子类自动生效自定义分页大小：在子类中重写pageSize getter特殊处理：子类可重写onRefresh或onLoadMore方法进行个性化处理总结通过模板方法模式，我们成功地将多Tab列表中的公共逻辑提取到基类中，同时保留了子类的灵活性。这种设计模式特别适用于具有相似流程但不同实现的场景，能够显著减少代码重复，提高项目的可维护性和扩展性。