NestedScrollView.png

import 'package:flutter/material.dart';

void main() {
  runApp(const MaterialApp(
    debugShowCheckedModeBanner: false,
    home: NestedTabBarView(),
  ));
}

class NestedScrollViewWidget extends StatelessWidget {
  const NestedScrollViewWidget({Key? key}) : super(key: key);

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      body: NestedScrollView(
        headerSliverBuilder: (BuildContext context, bool innerBoxIsScrolled) {
          return [
            SliverOverlapAbsorber(
              handle: NestedScrollView.sliverOverlapAbsorberHandleFor(context),
              sliver: SliverAppBar(
                snap: true,
                floating: true,
                expandedHeight: 200,
                forceElevated: innerBoxIsScrolled,
                flexibleSpace: FlexibleSpaceBar(
                  background: Image.network(
                    "https://upload.jianshu.io/admin_banners/web_images/5055/348f9e194f4062a17f587e2963b7feb0b0a5a982.png?imageMogr2/auto-orient/strip|imageView2/1/w/1250/h/540",
                    fit: BoxFit.cover,
                  ),
                ),
              ),
            ),
          ];
        },
        body: Builder(builder: (BuildContext context) {
          return CustomScrollView(
            slivers: [
              SliverOverlapInjector(
                handle:
                    NestedScrollView.sliverOverlapAbsorberHandleFor(context),
              ),
              buildSliverList(100)
            ],
          );
        }),
      ),
    );
  }

  Widget buildSliverList([int count = 5]) {
    return SliverFixedExtentList(
      delegate: SliverChildBuilderDelegate(
        (ctx, index) {
          return ListTile(
            leading: Text("Item $index"),
          );
        },
        childCount: count,
      ),
      itemExtent: 50,
    );
  }
}

class NestedTabBarView extends StatelessWidget {
  const NestedTabBarView({Key? key}) : super(key: key);

  @override
  Widget build(BuildContext context) {
    final _tabs = <String>['猜你喜欢', '今日特价', '发现更多'];

    return DefaultTabController(
      length: _tabs.length,
      child: Scaffold(
        body: NestedScrollView(
          headerSliverBuilder: (BuildContext context, bool innerBoxIsScrolled) {
            return [
              SliverOverlapAbsorber(
                handle:
                    NestedScrollView.sliverOverlapAbsorberHandleFor(context),
                sliver: SliverAppBar(
                  title: const Text('商城'),
                  floating: true,
                  snap: true,
                  forceElevated: innerBoxIsScrolled,
                  bottom: TabBar(
                    tabs: _tabs.map((String name) => Tab(text: name)).toList(),
                  ),
                ),
              ),
            ];
          },
          body: TabBarView(
            children: _tabs.map((String name) {
              return Builder(
                builder: (BuildContext context) {
                  return CustomScrollView(
                    key: PageStorageKey<String>(name),
                    slivers: [
                      SliverOverlapInjector(
                        handle: NestedScrollView.sliverOverlapAbsorberHandleFor(
                            context),
                      ),
                      SliverPadding(
                        padding: const EdgeInsets.all(8.0),
                        sliver: buildSliverList(50),
                      ),
                    ],
                  );
                },
              );
            }).toList(),
          ),
        ),
      ),
    );
  }

  Widget buildSliverList([int count = 5]) {
    return SliverFixedExtentList(
      delegate: SliverChildBuilderDelegate(
        (ctx, index) {
          return ListTile(
            leading: Text("Item $index"),
          );
        },
        childCount: count,
      ),
      itemExtent: 50,
    );
  }
}