How to convert ascii value in integer to its character equivalent in flutter?

In Dart, use these 2 functions to convert from int (byte) to String (char) and vice versa.

int value = ';'.codeUnitAt(0); //get unicode for semicolon

String char = String.fromCharCode(value); //get the semicolon string ;

This ia exactly what you need to generate your alphabet:

import 'dart:core';

void RandomString() {
  List<int> a = new List<int>.generate(26, (int index) => index + 65);
  String f = String.fromCharCodes(a);
  print(f);
}

void main() {
  RandomString();
}

Also You can copy, paste and test it here https://dartpad.dartlang.org/

You don't need dart:convert, you can just use String.fromCharCode

 print(String.fromCharCode(i));

More info: https://api.dartlang.org/stable/2.0.0/dart-core/String/String.fromCharCode.html