[flutter] How to run code after some delay in Flutter?

Trigger actions after countdown

Timer(Duration(seconds: 3), () {
  print("Yeah, this line is printed after 3 seconds");
});

Repeat actions

Timer.periodic(Duration(seconds: 5), (timer) {
  print(DateTime.now());
});

Trigger timer immediately

Timer(Duration(seconds: 0), () {
  print("Yeah, this line is printed immediately");
});