gist for flutter/flutter#34354

main.dart

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

void main() => runApp(MyApp());

class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      title: 'Flutter Demo',
      theme: ThemeData(
        primarySwatch: Colors.blue,
      ),
      home: MyHomePage()
    );
  }
}

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

  final String title;

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      body: Stack(
        children: <Widget>[

          ListView(
            children: <Widget>[
              Container(
                        height: 4000,
                        decoration: BoxDecoration(
                          gradient: LinearGradient(
                            colors: [const Color (0xFF8E78FF) , const Color (0xFFBA7AC9), const Color (0xFF9D79ED), const Color (0xFFE97C91)],
                            begin: Alignment.topCenter,
                            end: Alignment(1,0),
                            stops: [1,0.3,0.7,0],
                          )
                        ),
                      ),
            ],
          ),
          CustomScrollView(
            slivers: <Widget>[
              SliverAppBar(
                expandedHeight: 400,
                floating: true,
                centerTitle: true,
                title: Text("lasagna"),
                elevation: 0,
                forceElevated: true,
                backgroundColor: Colors.transparent,
              ),
              SliverList(
                delegate: SliverChildListDelegate(
                  [
                    Material(
                      elevation: 4,
                      color: Colors.transparent,
                      child: Container(
                        height: 900,
                        color:Colors.white12,
                        
                      ),
                    ),
                    Container(
                      height: 1000,
                      color:Colors.transparent
                    )
                  ]
                ),
              )
            ],
          )
        ],
      )
      
    );
  }
}