Image does not show on leading part of list tile when using Circle Avatar and back ground image - flutter

Question

I am building this app and just have a small UI problem. I am using a ListView builder. On the leading part of the tile, I want a circular icon to display with the desired image.
I believe my implementation is correct but when I run my code the circle avatar does come out on the leading part of the tile but it does not display the desired image. Instead, it just shows a blue circle on the leading end of each tile.
I am also getting an exception from the terminal. I will attach my code and the exception that I am getting. I would really appreciate suggestions from anyone. Thank you all!
import 'package:flutter/material.dart';
import 'package:url_launcher/url_launcher.dart';
void main() => runApp(MyApp());
class MyApp extends StatelessWidget {
List<String> titles = ["Covid-19 Cases", "Covid-19 Vaccine Tracker",
"Dr. John Campbell Youtube Channel", "Medcram YouTube Channel"];
List<String> files = ["cases.png", "vaccineIMG.png", "dr.johncampbell.png",
"Medcram.png"];
#override
Widget build(BuildContext context) {
return MaterialApp(
home: Scaffold(
backgroundColor: Colors.black54,
appBar: AppBar(
backgroundColor: Colors.redAccent,
title: Text("Your Covid-19 Briefing"),
),
body: ListView.builder(
itemCount: titles.length,
itemBuilder: (context, index) {
return Card(
child: ListTile(
onTap: () {
_launchUrl(index);
},
title: Text(
titles[index],
style: TextStyle(
fontSize: 20.0,
fontWeight: FontWeight.bold,
letterSpacing: 1.0,
color: Colors.black,
),
),
leading: CircleAvatar(
backgroundImage: AssetImage('assets/${files[index]}'),
),
),
);
}
),
),
);
}
_launchUrl(index) async {
List<String> _urlsToLaunch = [
"https://www.worldometers.info/coronavirus/",
"https://www.nytimes.com/interactive/2020/science/coronavirus-vaccine-tracker.html",
"https://www.youtube.com/c/Campbellteaching/videos/",
"https://www.youtube.com/c/Medcram/videos"
];
if (await canLaunch(_urlsToLaunch[index])) {
await launch(_urlsToLaunch[index]);
} else {
throw "Could not open $_urlsToLaunch";
}
}
}
Error:
════════ Exception caught by image resource service ════════════════════════════════════════════════
The following assertion was thrown resolving an image codec:
Unable to load asset: assets/cases.png
When the exception was thrown, this was the stack:
#0 PlatformAssetBundle.load (package:flutter/src/services/asset_bundle.dart:221:7)
<asynchronous suspension>
#1 AssetBundleImageProvider._loadAsync (package:flutter/src/painting/image_provider.dart:664:31)
#2 AssetBundleImageProvider.load (package:flutter/src/painting/image_provider.dart:648:14)
#3 ImageProvider.resolveStreamForKey.<anonymous closure> (package:flutter/src/painting/image_provider.dart:501:13)
...
Image provider: AssetImage(bundle: null, name: "assets/cases.png")
Image key: AssetBundleImageKey(bundle: PlatformAssetBundle#e7274(), name: "assets/cases.png", scale: 1.0)
════════════════════════════════════════════════════════════════════════════════════════════════════
════════ Exception caught by image resource service ════════════════════════════════════════════════
Unable to load asset: assets/vaccineIMG.png
════════════════════════════════════════════════════════════════════════════════════════════════════
════════ Exception caught by image resource service ════════════════════════════════════════════════
Unable to load asset: assets/dr.johncampbell.png
════════════════════════════════════════════════════════════════════════════════════════════════════
════════ Exception caught by image resource service ════════════════════════════════════════════════
Unable to load asset: assets/Medcram.png
════════════════════════════════════════════════════════════════════════════════════════════════════
pubspec.yaml file:
name: coronavirus_news_updates
description: A new Flutter application.
# The following line prevents the package from being accidentally published to
# pub.dev using `pub publish`. This is preferred for private packages.
publish_to: 'none' # Remove this line if you wish to publish to pub.dev
version: 1.0.0+1
environment:
sdk: ">=2.7.0 <3.0.0"
dependencies:
flutter:
sdk: flutter
url_launcher: ^5.4.11
# The following adds the Cupertino Icons font to your application.
# Use with the CupertinoIcons class for iOS style icons.
cupertino_icons: ^0.1.3
dev_dependencies:
flutter_test:
sdk: flutter
# For information on the generic Dart part of this file, see the
# following page: https://dart.dev/tools/pub/pubspec
# The following section is specific to Flutter.
flutter:
# The following line ensures that the Material Icons font is
# included with your application, so that you can use the icons in
# the material Icons class.
uses-material-design: true

Answer 1

Have you included your assets in your pubspec.yaml file?
flutter:
assets:
- assets/your_image_name.png
or to incude the entire folder:
flutter:
assets:
- assets/