Read and Write a Text File or Multiple Files in Flutter

With certain types of data, a text file can be preferred to other solution such as Shared Preferences, SQLite.

The file we are going to read and write needs to be in a sub-folder of assets folder and defined in pubspec.

Read data from a text file

Future<String> loadEmojiString(String fileName) async {
  return await rootBundle.loadString('assets/$fileName.txt');
}

Read multiple files

Future<Map<String, String>> loadAllFiles(List<Category> categories) async {
  final Map<String, String> map = Map<String, String>();
  for (var category in categories){
    String str = await rootBundle.loadString('assets/${category.id}.txt');
    map[category.id] = str;
  }
  return map;
}

Write data to a text file

To write data to a file, we need the help of path_provider package. Install the library and import it with:

import 'package:path_provider/path_provider.dart';

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