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Dart Timed Event Display
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| class HypotheticalService { | |
| final _stack = <Event>[]; | |
| Event? _lastDisplayed; | |
| void reportEvent(Event event) { | |
| print("${DateTime.now()} Adding ${event.runtimeType} to stack"); | |
| _stack.add(event); | |
| _outputLatest(); | |
| } | |
| void _outputLatest() { | |
| // Remove items that have reached their max display time | |
| _stack.removeWhere((e) => e.maxPassed); | |
| // If no pending events are left, output null | |
| if (_stack.isEmpty) return _display(null); | |
| // Display first from bottom of stack that hasn't been | |
| // displayed for its minimum display time yet. | |
| for (final item in _stack) { | |
| if (!item.minPassed) { | |
| _display(item); | |
| return; | |
| } | |
| } | |
| // If all have been displayed for their minimum time, just show newest | |
| _display(_stack[_stack.length - 1]); | |
| } | |
| void _display(Event? event) { | |
| if (_lastDisplayed == event) return; | |
| _lastDisplayed = event; | |
| if (event == null) { | |
| print("${DateTime.now()} DISPLAY: nothing"); | |
| return; | |
| } | |
| // We only start the timers once an item is displayed for the first time! | |
| if (!event.timersRunning) event.startTimers(_outputLatest); | |
| print("${DateTime.now()} DISPLAY: ${event.runtimeType}"); | |
| } | |
| } | |
| abstract class Event { | |
| get minTime; | |
| get maxTime; | |
| bool minPassed = false; | |
| bool maxPassed = false; | |
| bool timersRunning = false; | |
| Function? _callback; | |
| startTimers(Function callback) { | |
| timersRunning = true; | |
| _callback = callback; | |
| Future.delayed(Duration(seconds: minTime)).then(_onMinTimePassed); | |
| Future.delayed(Duration(seconds: maxTime)).then(_onMaxTimePassed); | |
| } | |
| void _onMinTimePassed(_) { | |
| print("${DateTime.now()} $runtimeType min time $minTime passed"); | |
| minPassed = true; | |
| if (_callback != null) _callback!(); | |
| } | |
| void _onMaxTimePassed(_) { | |
| print("${DateTime.now()} $runtimeType max time $maxTime passed"); | |
| maxPassed = true; | |
| if (_callback != null) _callback!(); | |
| } | |
| } | |
| class EventA extends Event { | |
| @override | |
| final minTime = 1; | |
| @override | |
| final maxTime = 3; | |
| } | |
| class EventB extends Event { | |
| @override | |
| final minTime = 2; | |
| @override | |
| final maxTime = 5; | |
| } | |
| class EventC extends Event { | |
| @override | |
| final minTime = 3; | |
| @override | |
| final maxTime = 7; | |
| } | |
| class EventD extends EventA {} | |
| void main() async { | |
| // Hypothetical service | |
| final service = HypotheticalService(); | |
| // Hypothetical UI reporting events | |
| service.reportEvent(EventA()); | |
| service.reportEvent(EventB()); | |
| service.reportEvent(EventC()); | |
| await Future.delayed(const Duration(seconds: 1)); | |
| service.reportEvent(EventD()); | |
| await Future.delayed(const Duration(minutes: 1)); | |
| } |
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