可以在其内部嵌套其他滚动视图的滚动视图，其滚动位置是固有链接的。

在普通的[ScrollView]中， 如果有一个Sliver组件容纳了一个[TabBarView]，它沿相反的方向滚动（例如，允许用户在标签所代表的页面之间水平滑动，而列表则垂直滚动），则该[TabBarView]内部的任何列表都不会相互作用 与外部[ScrollView]。 例如，浏览内部列表以滚动到顶部不会导致外部[ScrollView]中的[SliverAppBar]折叠以展开。

定义

const NestedScrollView({
  Key key,
  this.controller,    //滚动控制器，可以监听滚到的位置，设置滚动的位置等
  this.scrollDirection = Axis.vertical,    //滚动方向，分为垂直和水平方向。
  this.reverse = false,    //表示反转滚动方向，并不是有垂直转为水平，而是垂直方向滚动时，默认向下滚动，
  this.physics,    //表示可滚动组件的物理滚动特性
  @required this.headerSliverBuilder,
  @required this.body,
  this.dragStartBehavior = DragStartBehavior.start,
  this.floatHeaderSlivers = false,
  this.clipBehavior = Clip.hardEdge,
  this.restorationId,
})

示例：滚动隐藏AppBar

import 'package:flutter/material.dart';
class ScrollDemo3 extends StatefulWidget {
  @override
  _ScrollDemo3State createState() => _ScrollDemo3State();
}
class _ScrollDemo3State extends State<ScrollDemo3> {
  @override
  Widget build(BuildContext context) {
    return NestedScrollView(
      headerSliverBuilder: (BuildContext context, bool innerBoxIsScrolled) {
        return [
          SliverAppBar(
            title: Text('hello flutter'),
          ),
        ];
      },
      body: Container(
        child: ListView.builder(
          itemCount: 20,
          itemBuilder: (context, index) {
            return Container(
              height: 80,
              color: Colors.primaries[index % Colors.primaries.length],
              alignment: Alignment.center,
              child: Text('文本 $index', style: TextStyle(color: Colors.white, fontSize: 20)),
            );
          },
        ),
      ),
    );
  }
}

示例：SliverAppBar 展开折叠

headerSliverBuilder: (BuildContext context, bool innerBoxIsScrolled) {
  return [
    SliverAppBar(
      expandedHeight: 230.0,
      // title: Text('hello flutter'),
      pinned: true,
      flexibleSpace: FlexibleSpaceBar(
        title: Text('复仇者联盟'),
        background: Image.network(
          'http://img.haote.com/upload/20180918/2018091815372344164.jpg',
          fit: BoxFit.fill,
        ),
      ),
    ),
  ];
},

示例：与TabBar配合使用

import 'package:flutter/material.dart';
class ScrollDemo3 extends StatefulWidget {
  @override
  _ScrollDemo3State createState() => _ScrollDemo3State();
}
class _ScrollDemo3State extends State<ScrollDemo3> with SingleTickerProviderStateMixin {
  TabController _tabController; //tab控制器
  @override
  void initState() {
    super.initState();
    _tabController = TabController(length: 2, vsync: this);
  }
  @override
  Widget build(BuildContext context) {
    return NestedScrollView(
      headerSliverBuilder: (BuildContext context, bool innerBoxIsScrolled) {
        return [
          SliverAppBar(
            expandedHeight: 230.0,
            pinned: true,
            flexibleSpace: FlexibleSpaceBar(
              title: Text('复仇者联盟'),
              background: Image.network(
                'http://img.haote.com/upload/20180918/2018091815372344164.jpg',
                fit: BoxFit.fill,
              ),
            ),
          ),
          SliverList(
            delegate: SliverChildListDelegate([
              Text('fsdfs'),
            ]),
          ),
          SliverPersistentHeader(
            pinned: true,
            // floating: true,
            delegate: StickySliverPersistentHeader(
              child: TabBar(
                controller: _tabController,
                tabs: [
                  Tab(text: '咨询'),
                  Tab(text: '技术'),
                ],
              ),
            ),
          ),
        ];
      },
      body: Container(
        child: TabBarView(
          controller: _tabController,
          children: [
            ListView.builder(
              itemCount: 20,
              itemBuilder: (context, index) {
                return Container(
                  height: 80,
                  color: Colors.primaries[index % Colors.primaries.length],
                  alignment: Alignment.center,
                  child: Text('咨询 $index', style: TextStyle(color: Colors.white, fontSize: 20)),
                );
              },
            ),
            ListView.builder(
              itemCount: 20,
              itemBuilder: (context, index) {
                return Container(
                  height: 80,
                  color: Colors.primaries[index % Colors.primaries.length],
                  alignment: Alignment.center,
                  child: Text('技术 $index', style: TextStyle(color: Colors.white, fontSize: 20)),
                );
              },
            ),
          ],
        ),
      ),
    );
  }
}
class StickySliverPersistentHeader extends SliverPersistentHeaderDelegate {
  final child;
  StickySliverPersistentHeader({@required this.child});
  @override
  Widget build(BuildContext context, double shrinkOffset, bool overlapsContent) {
    return Container(
      color: Colors.green,
      child: this.child,
    );
  }
  @override
  double get minExtent => this.child.preferredSize.height;
  double get maxExtent => this.child.preferredSize.height;
  @override
  bool shouldRebuild(covariant SliverPersistentHeaderDelegate oldDelegate) {
    return true;
  }
}