mapEventToState仅触发一次

基本上，而不是屈服* _counterStream你需要得到这个IE中的状态

Active

Inactive

改变这个

    if (event is ActiveEvent) {      _counter.add(Active(active: true, count: currentState.count));      yield* _counterStream;    } else if (event is InactiveEvent) {      _counter.add(Inactive(active: false, count: currentState.count));      yield* _counterStream;    }

对此

    if (event is ActiveEvent) {      yield Inactive(active: false, count: currentState.count);    } else if (event is InactiveEvent) {      yield Active(active: true, count: currentState.count);    }