why this flutter staggered grid view is not working

i experiemented with flutter staggered gridview to add header tile at the top of grid view but this code is not working

Please help me solve this mess.

FIRST ERROR SAYS - the constructor return type 'dynamic' that is not of expected type widget

SECOND ERROR SAYS:- THe declaration _ImageTile is not referenced

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

List<StaggeredTile> _staggeredTiles = const <StaggeredTile>[
  const StaggeredTile.count(2, 2),
  const StaggeredTile.count(2, 2),
  const StaggeredTile.count(2, 2),
  const StaggeredTile.count(2, 2),
  const StaggeredTile.count(2, 2),
  const StaggeredTile.count(2, 2),
  const StaggeredTile.count(2, 2),
  const StaggeredTile.count(2, 2),
  const StaggeredTile.count(2, 2),
  const StaggeredTile.count(2, 2),
];


List<Widget> _tiles = <Widget>[
  const HomeHeaderTile('Heading of app', Colors.indigo),
  const HomeTile('GRID1', Colors.indigo, 'https://picsum.photos/200/300/?random'),
  const HomeTile('GRID2', Colors.indigo, 'https://picsum.photos/200/300/?random'),
  const HomeTile('GRID3', Colors.indigo, 'https://picsum.photos/200/300/?random'),
  const HomeTile('GRID4', Colors.indigo, 'https://picsum.photos/200/300/?random'),
  const HomeTile('GRID5', Colors.indigo, 'https://picsum.photos/200/300/?random'),
  const HomeTile('GRID6', Colors.indigo, 'https://picsum.photos/200/300/?random'),
  const HomeTile('GRID7', Colors.indigo, 'https://picsum.photos/200/300/?random'),
  const HomeTile('GRID8', Colors.indigo, 'https://picsum.photos/200/300/?random'),
  const HomeTile('GRID9', Colors.indigo, 'https://picsum.photos/200/300/?random'),
  const HomeTile('GRID10', Colors.indigo, 'https://picsum.photos/200/300/?random'),



];








//List<Widget> _tiles = const <Widget>[
//  const _ImageTile('https://picsum.photos/200/300/?random'),
//  const _ImageTile('https://picsum.photos/201/300/?random'),
//  const _ImageTile('https://picsum.photos/202/300/?random'),
//  const _ImageTile('https://picsum.photos/203/300/?random'),
//  const _ImageTile('https://picsum.photos/204/300/?random'),
//  const _ImageTile('https://picsum.photos/205/300/?random'),
//  const _ImageTile('https://picsum.photos/206/300/?random'),
//  const _ImageTile('https://picsum.photos/207/300/?random'),
//  const _ImageTile('https://picsum.photos/208/300/?random'),
//  const _ImageTile('https://picsum.photos/209/300/?random'),
//];

class ImageTile extends StatelessWidget {
  @override

  Widget build(BuildContext context) {
    return   Scaffold(

        body:Padding(
            padding: const EdgeInsets.only(top: 12.0),
            child:   StaggeredGridView.count(
              crossAxisCount: 4,
              staggeredTiles: _staggeredTiles,
              children: _tiles,

              mainAxisSpacing: 4.0,
              crossAxisSpacing: 4.0,
            )));
  }
}

class _ImageTile extends StatelessWidget {
  const _ImageTile(this.gridImage);

  final gridImage;

  @override
  Widget build(BuildContext context) {
    return   Card(
      color: const Color(0x00000000),
      elevation: 3.0,
      child:   InkWell(
       // onTap: ()=>


        child:   Container(
            decoration:   BoxDecoration(
              image: DecorationImage(
                image:NetworkImage(gridImage),
                fit: BoxFit.cover,
              ),
              borderRadius:   BorderRadius.all(const Radius.circular(10.0)),
            )
        ),
      ),
    );
  }}

If you need more info then please comment.Thank you