How to fix undefined File() class and its methods in Dart? - dart

Question

I want to save files in local storage of Android/iOS. I followed the Flutter cookbook to save files but it didn't work. There are examples everywhere using the File class, but it's undefined when I use it. I'm using Dart 2.2.0 and Flutter 1.2.1
I've tried example code snippets from a few websites. Nothing worked. File class, readAsString, and writeAsString are undefined in my Dart file.
Here's the code. Checked it in DartPad. Where am I wrong?
//packages
import 'dart:io';
import 'dart:async';
import 'package:path_provider/path_provider.dart';
//start
class File {
/// Directory Path
/// Local Directory Path
Future<String> get _localPath async {
final directory = await getApplicationDocumentsDirectory();
// For your reference print the AppDoc directory
print(directory.path);
return directory.path;
}
/// Reference for file Location
Future<File> get _localFile async {
final path = await _localPath;
final address = '$path/data.txt';
return File(address);
}
/// Presenting different Data as 1 String
String convertingtoString(String title, String author, String content) {
return '$title\n$author\n\n$content';
}
/// Write to file
/// Writing as String
Future<File> writeContent(String matter) async {
/// Get matter converted to string as matter
final file = await _localFile;
// Write the file
return file.writeAsString(matter);
}
/// Read from file
Future<String> readcontent() async {
try {
final file = await _localFile;
// Read the file
String contents = await file.readAsString();
return contents;
} catch (e) {
// If there is an error reading, return a default String
return 'Error, Couldn\'t read file';
}
}
}
This is code from my android flutter project. I get the same errors like DartPad in VScode

Answer 1

You've created your own class named File, so that hides the File class from dart:io. Name your custom class something else, or do:
import 'dart:io' as io;
and use io.File where you intend to use dart:io's File class. (I recommend renaming your custom class to avoid confusion.)
Original answer
Since you have import 'dart:io';, the File class should be available to you.
If you're trying this solely with DartPad, then it (among other things) won't work there because dart:io is meant to be used with a Dart VM. dart:io won't work in a browser, which has a sandboxed environment and generally prevents filesystem access:
Important: Browser-based applications can't use this library. Only servers, command-line scripts, and Flutter mobile apps can import and use dart:io.