How to read and write a text file in Flutter

问题:

How do you read text from a file and write text to a file?

I've been learning about how to read and write text to and from a file. I found another question about reading from assets, but that is not the same. I will add my answer below from what I learned from the documentation.

回答1:

Setup

Add the following plugin in pubspec.yaml:

dependencies:
  path_provider: ^0.4.1

Update the version number to whatever is current.

And import it in your code.

import 'package:path_provider/path_provider.dart';

You also have to import dart:io to use the File class.

import 'dart:io';

Writing to a text file

_write(String text) async {
  final Directory directory = await getApplicationDocumentsDirectory();
  final File file = File('${directory.path}/my_file.txt');
  await file.writeAsString(text);
}

Reading from a text file

Future<String> _read() async {
  String text;
  try {
    final Directory directory = await getApplicationDocumentsDirectory();
    final File file = File('${directory.path}/my_file.txt');
    text = await file.readAsString();
  } catch (e) {
    print("Couldn't read file");
  }
  return text;
}

Notes

• You can also get the path string with join(directory.path, 'my_file.txt') but you need to import 'package:path/path.dart'.
• Flutter's Official Documentation of Reading and Writing Files