insertItem method
Implementation
@override
void insertItem(int index, {Duration duration = animationDuration}) {
if (_listKey.currentState == null) throw Exception(_errorMsg);
_listKey.currentState!.insertItem(index, duration: duration);
}
@override
void insertItem(int index, {Duration duration = animationDuration}) {
if (_listKey.currentState == null) throw Exception(_errorMsg);
_listKey.currentState!.insertItem(index, duration: duration);
}