void main() {
String test = "10:12:23.24";
String hr = test.split(":")[0];
// print(hr);
String minutes = test.split(":")[1];
// print(minutes);
String seconds = test.split(":")[2].split(".")[0];
// print(seconds);
String milliseconds = test.split(":")[2].split(".")[1];
// print(milliseconds);

Duration duration = Duration(
  hours: int.tryParse(hr) ?? 0,
  minutes: int.tryParse(minutes) ?? 0,
  seconds: int.tryParse(seconds) ?? 0,
  milliseconds: int.tryParse(milliseconds) ?? 0);
  print(duration.inMilliseconds);
}