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- typedef void EventCallback(arg);
- class EventBus {
-
- EventBus._internal();
-
- static EventBus _singleton = EventBus._internal();
-
- factory EventBus() => _singleton;
-
- var _emap = Map<Object, List<EventCallback>?>();
-
- void on(eventName, EventCallback f) {
- if (eventName == null) return;
- _emap[eventName] ??= [];
- _emap[eventName]!.add(f);
- }
-
- void off(eventName, [EventCallback? f]) {
- var list = _emap[eventName];
- if (eventName == null || list == null) return;
- if (f == null) {
- _emap[eventName] = null;
- } else {
- list.remove(f);
- }
- }
-
- void emit(eventName, [arg]) {
- var list = _emap[eventName];
- if (list == null) return;
- int len = list.length - 1;
-
- for (var i = len; i > -1; --i) {
- list[i](arg);
- }
- }
- }
- var eventBus = EventBus();
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