问题
I am trying to replace didRotateFromInterfaceOrientation with willTransitionToTraitCollection - in a UIViewController subclass - as doc says, but method is not get called when I am rotating device. Why?
回答1:
If you're testing this on iPad it has regular trait collections for vertical and horizontal class for both orientations, thus it will not call this method when orientation changed.
来源：https://stackoverflow.com/questions/25634085/willtransitiontotraitcollection-not-get-called-why