如果在viewWillAppear中调用scrollToItemAtIndexPath，则不会在UICollectionView上更新contentOffset

I have a UICollectionView that is used to simulate the new calendar in iOS 7. This collection view is inside a controller that has a selectedDate property. Whenever the selectedDate property is set the collection view should scroll to the date in the collection view.I have a UICollectionView that is used to simul