iOS：旋转iPad，什么时候可以改变视角？

Question

My app has very different UI structures for each orientation.

At what stage in the rotation lifecycle of an iPad should I remove, then add the orientation's UI to ensure the smoothest transition?

Answer 1

When handling autorotation, you have 4 main methods to care about:

shouldAutorotateToInterfaceOrientation:(UIInterfaceOrientation)interfaceOrientation

willAnimateRotationToInterfaceOrientation:(UIInterfaceOrientation)interfaceOrientation                                   duration:(NSTimeInterval)duration

willRotateToInterfaceOrientation:(UIInterfaceOrientation)toInterfaceOrientation
                            duration:(NSTimeInterval)duration

didRotateFromInterfaceOrientation:(UIInterfaceOrientation)fromInterfaceOrientation

Now, the way I handle the rotation is, eg:

1. adjust all the frames in willAnimateRotationToInterfaceOrientation ;

2. add/remove subviews (if needed) in willRotateToInterfaceOrientation ;

3. restore subviews (if needed) in didRotateFromInterfaceOrientation .

More in general, I modify all properties that are animatable in willAnimateRotationToInterfaceOrientation ; while I do all modifications that are not animatable in willRotateToInterfaceOrientation / didRotateFromInterfaceOrientation .

This is what the UIViewController reference says about willRotate / didRotate :

To temporarily turn off features that are not needed or might otherwise cause problems during the orientation change, you can override the willRotateToInterfaceOrientation:duration: method and perform the needed actions there. You can then override the didRotateFromInterfaceOrientation: method and use it to reenable those features once the orientation change is complete.