如何将CustomScrollView中的SliverAppBar与SliverFixedExtentList集成在一起，以及如何使用可滚动标签的脚手架？

CustomScrollView(
  slivers: <Widget>[
    SliverAppBar(
      title: Text('My App'),
      backgroundColor: Colors.blue,
      floating: true,
    ),
    SliverFixedExtentList(
      itemExtent: 50.0,
      delegate: SliverChildBuilderDelegate(
        (BuildContext context, int index) {
          return ListTile(
            title: Text('Item $index'),
          );
        },
        childCount: 20,
      ),
    ),
  ],
)

import 'package:flutter_staggered_grid_view/flutter_staggered_grid_view.dart';

StaggeredGridView.count(
  crossAxisCount: 4,
  children: <Widget>[
    StaggeredTile.count(2, 2),
    StaggeredTile.count(2, 1),
    StaggeredTile.count(2, 1),
    StaggeredTile.count(4, 1),
    StaggeredTile.count(4, 2),
  ],
  children: <Widget>[
    Container(color: Colors.green),
    Container(color: Colors.blue),
    Container(color: Colors.red),
    Container(color: Colors.orange),
    Container(color: Colors.purple),
  ],
)