如何创建一个与颤振中的小部件滚动同步的标签栏？

Question

基本上我想要在这里完成的是有一个水平的类别列表（可以是 TabBar）和一个垂直的类别列表，每个类别中都有项目列表。

当你点击一个类别时，它应该滚动到类别垂直列表中的一个位置。并且当你滚动垂直列表时，顶部的活动类别也应该更新当前活动类别。

我在 FoodPanda 应用程序中看到过此功能，但我无法复制它。

关于如何实现此功能有什么建议吗？

这是 UI 的屏幕截图。

Answer 1

您可以复制粘贴运行下面的完整代码
您可以使用包 https://pub.dev/packages/scrollable_list_tabview
代码片段

body: ScrollableListTabView(
        tabHeight: 48,
        bodyAnimationDuration: const Duration(milliseconds: 150),
        tabAnimationCurve: Curves.easeOut,
        tabAnimationDuration: const Duration(milliseconds: 200),
        tabs: [
          ScrollableListTab(
              tab: ListTab(
                  label: Text('Vegetables'),
                  icon: Icon(Icons.group),
                  showIconOnList: false),
              body: ListView.builder(
                shrinkWrap: true,
                physics: NeverScrollableScrollPhysics(),
                itemCount: 10,
                itemBuilder: (_, index) => ListTile(
                  leading: Container(
                    height: 40,
                    width: 40,
                    decoration: BoxDecoration(
                        shape: BoxShape.circle, color: Colors.grey),
                    alignment: Alignment.center,
                    child: Text(index.toString()),
                  ),
                  title: Text('Vegetables element $index'),
                ),
              )),
          ScrollableListTab(
              tab: ListTab(label: Text('Fruits'), icon: Icon(Icons.add)),
              body: ListView.builder(
                shrinkWrap: true,
                physics: NeverScrollableScrollPhysics(),

工作演示

完整代码

import 'package:flutter/material.dart';
import 'package:scrollable_list_tabview/scrollable_list_tabview.dart';

void main() {
  runApp(MyApp());
}

class MyApp extends StatelessWidget {
  // This widget is the root of your application.
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      title: 'Flutter Demo',
      debugShowCheckedModeBanner: false,
      theme: ThemeData(
        primarySwatch: Colors.blue,
        visualDensity: VisualDensity.adaptivePlatformDensity,
      ),
      home: MyHomePage(title: 'Flutter ScrollableListTabView Example'),
    );
  }
}

class MyHomePage extends StatefulWidget {
  MyHomePage({Key key, this.title}) : super(key: key);

  final String title;

  @override
  _MyHomePageState createState() => _MyHomePageState();
}

class _MyHomePageState extends State<MyHomePage> {
  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: Text(widget.title),
      ),
      body: ScrollableListTabView(
        tabHeight: 48,
        bodyAnimationDuration: const Duration(milliseconds: 150),
        tabAnimationCurve: Curves.easeOut,
        tabAnimationDuration: const Duration(milliseconds: 200),
        tabs: [
          ScrollableListTab(
              tab: ListTab(
                  label: Text('Vegetables'),
                  icon: Icon(Icons.group),
                  showIconOnList: false),
              body: ListView.builder(
                shrinkWrap: true,
                physics: NeverScrollableScrollPhysics(),
                itemCount: 10,
                itemBuilder: (_, index) => ListTile(
                  leading: Container(
                    height: 40,
                    width: 40,
                    decoration: BoxDecoration(
                        shape: BoxShape.circle, color: Colors.grey),
                    alignment: Alignment.center,
                    child: Text(index.toString()),
                  ),
                  title: Text('Vegetables element $index'),
                ),
              )),
          ScrollableListTab(
              tab: ListTab(label: Text('Fruits'), icon: Icon(Icons.add)),
              body: ListView.builder(
                shrinkWrap: true,
                physics: NeverScrollableScrollPhysics(),
                itemCount: 10,
                itemBuilder: (_, index) => ListTile(
                  leading: Container(
                    height: 40,
                    width: 40,
                    decoration: BoxDecoration(
                        shape: BoxShape.circle, color: Colors.grey),
                    alignment: Alignment.center,
                    child: Text(index.toString()),
                  ),
                  title: Text('Fruits element $index'),
                ),
              )),
          ScrollableListTab(
              tab: ListTab(label: Text('Meat'), icon: Icon(Icons.group)),
              body: ListView.builder(
                shrinkWrap: true,
                physics: NeverScrollableScrollPhysics(),
                itemCount: 10,
                itemBuilder: (_, index) => ListTile(
                  leading: Container(
                    height: 40,
                    width: 40,
                    decoration: BoxDecoration(
                        shape: BoxShape.circle, color: Colors.grey),
                    alignment: Alignment.center,
                    child: Text(index.toString()),
                  ),
                  title: Text('Meat element $index'),
                ),
              )),
          ScrollableListTab(
              tab: ListTab(
                  label: Text('Herbs&Spices'), icon: Icon(Icons.subject)),
              body: GridView.builder(
                shrinkWrap: true,
                gridDelegate: SliverGridDelegateWithFixedCrossAxisCount(
                    crossAxisCount: 2),
                physics: NeverScrollableScrollPhysics(),
                itemCount: 10,
                itemBuilder: (_, index) => Card(
                  child: Center(child: Text('Herbs&Spices element $index')),
                ),
              )),
          ScrollableListTab(
              tab: ListTab(
                  label: Text('Egg'),
                  icon: Icon(Icons.subject),
                  showIconOnList: true),
              body: GridView.builder(
                shrinkWrap: true,
                gridDelegate: SliverGridDelegateWithFixedCrossAxisCount(
                    crossAxisCount: 2),
                physics: NeverScrollableScrollPhysics(),
                itemCount: 10,
                itemBuilder: (_, index) => Card(
                  child: Center(child: Text('Egg element $index')),
                ),
              )),
        ],
      ),
    );
  }
}

Answer 2

我尝试了几种方法，但这似乎最适合我。

包：

scroll_to_index: ^2.0.0 
rect_getter: ^1.0.0

rect_getter 的用法灵感来自：https://gist.github.com/debuggerx01/49f108d68ed903458e9478b4f0c186f4

代码（食物熊猫克隆）：

import 'package:flutter/material.dart';
import 'package:scroll_to_index/scroll_to_index.dart';
import 'package:food_panda_sticky_header/colors.dart';
import 'package:food_panda_sticky_header/example_data.dart';
import 'package:food_panda_sticky_header/widgets/widgets.dart';
import 'package:rect_getter/rect_getter.dart';

class HomeScreen extends StatefulWidget {
  @override
  _HomeScreenState createState() => _HomeScreenState();
}

class _HomeScreenState extends State<HomeScreen> with SingleTickerProviderStateMixin {
  bool isCollapsed = false;
  late AutoScrollController scrollController;
  late TabController tabController;

  final double expandedHeight = 500.0;
  final PageData data = ExampleData.data;
  final double collapsedHeight = kToolbarHeight;

  final listViewKey = RectGetter.createGlobalKey();
  Map<int, dynamic> itemKeys = {};

  // prevent animate when press on tab bar
  bool pauseRectGetterIndex = false;

  @override
  void initState() {
    tabController = TabController(length: data.categories.length, vsync: this);
    scrollController = AutoScrollController();
    super.initState();
  }

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

  List<int> getVisibleItemsIndex() {
    Rect? rect = RectGetter.getRectFromKey(listViewKey);
    List<int> items = [];
    if (rect == null) return items;
    itemKeys.forEach((index, key) {
      Rect? itemRect = RectGetter.getRectFromKey(key);
      if (itemRect == null) return;
      if (itemRect.top > rect.bottom) return;
      if (itemRect.bottom < rect.top) return;
      items.add(index);
    });
    return items;
  }

  void onCollapsed(bool value) {
    if (this.isCollapsed == value) return;
    setState(() => this.isCollapsed = value);
  }

  bool onScrollNotification(ScrollNotification notification) {
    if (pauseRectGetterIndex) return false;
    int lastTabIndex = tabController.length - 1;
    List<int> visibleItems = getVisibleItemsIndex();

    bool reachLastTabIndex = visibleItems.length <= 2 && visibleItems.last == lastTabIndex;
    if (reachLastTabIndex) {
      tabController.animateTo(lastTabIndex);
    } else {
      int sumIndex = visibleItems.reduce((value, element) => value + element);
      int middleIndex = sumIndex ~/ visibleItems.length;
      if (tabController.index != middleIndex) tabController.animateTo(middleIndex);
    }

    return false;
  }

  void animateAndScrollTo(int index) {
    pauseRectGetterIndex = true;
    tabController.animateTo(index);
    scrollController
        .scrollToIndex(index, preferPosition: AutoScrollPosition.begin)
        .then((value) => pauseRectGetterIndex = false);
  }

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      extendBodyBehindAppBar: true,
      backgroundColor: scheme.background,
      body: RectGetter(
        key: listViewKey,
        child: NotificationListener<ScrollNotification>(
          child: buildSliverScrollView(),
          onNotification: onScrollNotification,
        ),
      ),
    );
  }

  Widget buildSliverScrollView() {
    return CustomScrollView(
      physics: const ClampingScrollPhysics(),
      controller: scrollController,
      slivers: [
        buildAppBar(),
        buildBody(),
      ],
    );
  }

  SliverAppBar buildAppBar() {
    return FAppBar(
      data: data,
      context: context,
      scrollController: scrollController,
      expandedHeight: expandedHeight,
      collapsedHeight: collapsedHeight,
      isCollapsed: isCollapsed,
      onCollapsed: onCollapsed,
      tabController: tabController,
      onTap: (index) => animateAndScrollTo(index),
    );
  }

  SliverList buildBody() {
    return SliverList(
      delegate: SliverChildListDelegate(
        List.generate(data.categories.length, (index) {
          itemKeys[index] = RectGetter.createGlobalKey();
          return buildCategoryItem(index);
        }),
      ),
    );
  }

  Widget buildCategoryItem(int index) {
    Category category = data.categories[index];
    return RectGetter(
      key: itemKeys[index],
      child: AutoScrollTag(
        key: ValueKey(index),
        index: index,
        controller: scrollController,
        child: CategorySection(category: category),
      ),
    );
  }
}

演示： https://github.com/theacheng/food_panda_sticky_header/pull/4

如何创建一个与颤振中的小部件滚动同步的标签栏？

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