Flutter/Dart: How to sleep for X seconds/milliseconds

As a brief note, these are two different ways to do a “sleep” call in Flutter/Dart, depending on your needs:

// inside an async method
await Future.delayed(const Duration(milliseconds: 250));

// not in an async method
sleep(const Duration(milliseconds: 250));

As shown, the first approach is for when you want an async/await approach, and the second sleep method is for when you are doing things in serial order (as opposed to a parallel/concurrent approach).