SliverGrid 和 SliverPadding 简单样例

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

class SliverGridAndSliverPaddingDemo extends StatefulWidget{
  @override
  _SliverGridAndSliverPaddingDemoState createState()=>_SliverGridAndSliverPaddingDemoState();
}
class _SliverGridAndSliverPaddingDemoState extends State{
  @override
  void initState() {
    // TODO: implement initState
    super.initState();
  }
  @override
  void dispose() {
    // TODO: implement dispose
    super.dispose();
  }
  @override
  Widget build(BuildContext context) {
    // TODO: implement build
    return Scaffold(
      appBar: null,
      body: CustomScrollView(
        slivers: [
          SliverAppBar(
            expandedHeight: 250.0,
            title: Text('SliverGrid和SliverPadding简单样例',),
            flexibleSpace: FlexibleSpaceBar(
              //标题
              title: Text('flexibleSpaceBar',style: Text