Flutter NetworkImage memory issue

main.dart

import 'dart:math';

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

void main() {
  runApp(MyApp());
}

class MyApp extends StatelessWidget {
  // This widget is the root of your application.
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      title: 'Flutter Memory Issue',
      theme: ThemeData(
        primarySwatch: Colors.blue,
      ),
      home: MyHomePage(
        title: 'Flutter Demo Home Page',
        imageUrl: "https://picsum.photos/",
      ),
    );
  }
}

class GalleryImage extends StatelessWidget {
  final String url;
  final int height;
  final int width;
  GalleryImage(this.url, this.height, this.width);

  @override
  Widget build(BuildContext context) {
    return Container(
      width: (MediaQuery.of(context).size.width / 3),
      height: height * (MediaQuery.of(context).size.width / 3) / width,
      decoration: BoxDecoration(
        image: DecorationImage(
          image: NetworkImage(
            url,
          ),
          fit: BoxFit.cover,
        ),
      ),
    );
  }
}

class MyHomePage extends StatefulWidget {
  MyHomePage(
      {Key key, this.title, this.imageUrl})
      : super(key: key);
  final String imageUrl;

  final String title;

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

class _MyHomePageState extends State<MyHomePage> {
  static var _random = new Random();
  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: Text(widget.title),
      ),
      body: Center(
        child: Column(
          mainAxisAlignment: MainAxisAlignment.center,
          children: <Widget>[
            Expanded(
              child: CustomScrollView(
                slivers: <Widget>[
                  SliverStaggeredGrid.countBuilder(
                    crossAxisCount: 3,
                    itemCount: 100,
                    itemBuilder: (BuildContext context, int index) {
                      int width = 100 + _random.nextInt(1800);
                      return GestureDetector(
                        onTap: () {
                          Navigator.push(
                              context,
                              MaterialPageRoute(
                                  builder: (BuildContext context) => MyHomePage(
                                        title: 'Flutter Demo Home Page',
                                        imageUrl: widget.imageUrl,
                                      )));
                        },
                        child: GalleryImage(widget.imageUrl + width.toString(), width,
                            width),
                      );
                    },
                    staggeredTileBuilder: (int index) => StaggeredTile.fit(1),
                    mainAxisSpacing: 0,
                    crossAxisSpacing: 0,
                  ),
                ],
              ),
            ),
          ],
        ),
      ),
    );
  }
}