A very simple (50 lines of code, see Git rep) flutter package for animating a counter that decrements or increments an integer.
The package can be tweaked with duration.
To use this plugin, add counter_animation as dependency to pubspec.yaml file.
The code below shows an integer that counts up to 50, while easing out.
import 'package:flutter/material.dart';
import 'package:counter_animation/counter_animation.dart';
CounterAnimation(
begin: 0,
end: 50,
duration: 5,
curve: Curves.easeOut,
textStyle: textStyle
),