OS Error: No such file or directory, errno = 2

please use rootBundle to load assetshttps://flutter.dev/docs/development/ui/assets-and-images

import 'dart:async' show Future;import 'package:flutter/services.dart' show rootBundle;Future<String> loadAsset() async {  return await rootBundle.loadString('assets/config.json');}

If you are trying load html file for webview, please reference this https://inducesmile.com/google-flutter/how-load-a-local-html-file-in-flutter-webview/

Future<String> _loadLocalHTML() async {  return await rootBundle.loadString('assets/html_code.html');}

code from reference document

import 'package:flutter/material.dart';import 'package:flutter/services.dart';import 'package:flutter_webview_plugin/flutter_webview_plugin.dart';import 'dart:async';class LoadHTMLFileToWEbView extends StatefulWidget {  @override  _LoadHTMLFileToWEbViewState createState() => _LoadHTMLFileToWEbViewState();}class _LoadHTMLFileToWEbViewState extends State<LoadHTMLFileToWEbView> {  @override  Widget build(BuildContext context) {    return FutureBuilder<String>(      future: _loadLocalHTML(),      builder: (context, snapshot) {        if (snapshot.hasData) {          return WebviewScaffold(            appBar: AppBar(title: Text("Load HTM file in WebView")),            withJavascript: true,            appCacheEnabled: true,            url: new Uri.dataFromString(snapshot.data, mimeType: 'text/html')                .toString(),          );        } else if (snapshot.hasError) {          return Scaffold(            body: Center(              child: Text("${snapshot.error}"),            ),          );        }        return Scaffold(          body: Center(child: CircularProgressIndicator()),        );      },    );  }}Future<String> _loadLocalHTML() async {  return await rootBundle.loadString('assets/html_code.html');}