copy.dart

import 'package:flutter/material.dart';

class DemoPage extends StatefulWidget {
  DemoPage({Key key}) : super(key: key);

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

class _DemoPageState extends State<DemoPage> {
  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: Text('Material App Bar'),
      ),
      body: Center(
        child: Container(
          child: customWidget(),
        ),
      ),
    );
  }

  customWidget() => CustomScrollView(
        slivers: <Widget>[
          const SliverAppBar(
            pinned: true,
            expandedHeight: 250.0,
            flexibleSpace: FlexibleSpaceBar(
              title: Text('Demo'),
            ),
          ),
          SliverGrid(
            gridDelegate: SliverGridDelegateWithMaxCrossAxisExtent(
              maxCrossAxisExtent: 200.0,
              mainAxisSpacing: 10.0,
              crossAxisSpacing: 10.0,
              childAspectRatio: 4.0,
            ),
            delegate: SliverChildBuilderDelegate(
              (BuildContext context, int index) {
                return Container(
                  alignment: Alignment.center,
                  color: Colors.teal[100 * (index % 9)],
                  child: Text('Grid Item $index'),
                );
              },
              childCount: 20,
            ),
          ),
          SliverFixedExtentList(
            itemExtent: 50.0,
            delegate: SliverChildBuilderDelegate(
              (BuildContext context, int index) {
                return Container(
                  alignment: Alignment.center,
                  color: Colors.lightBlue[100 * (index % 9)],
                  child: Text('List Item $index'),
                );
              },
            ),
          ),
        ],
      );
}