formatDuration method
Implementation
String formatDuration(int timeCount) {
int hour = timeCount ~/ 3600;
String hourShow = hour <= 9 ? "0$hour" : "$hour";
int minute = (timeCount % 3600) ~/ 60;
String minuteShow = minute <= 9 ? "0$minute" : "$minute";
int second = timeCount % 60;
String secondShow = second <= 9 ? "0$second" : "$second";
return '$hourShow:$minuteShow:$secondShow';
}