This question already has an answer here:
It seems all the current iOS devices maps to the new iOS 8 size classes nicely except iPad landscape? I seem not able to figure out how to use the size class feature to draw a different scene for iPad landscape (different from iPad portrait)?
Is that intended by design in Apple's mind or am I miss something about the iOS size classes?
It appears to be Apple's intent to treat both iPad orientations as the same -- but as a number of us are finding, there are very legitimate design reasons to want to vary the UI layout for iPad Portrait vs. iPad Landscape.
However, I believe I have an answer for adapting size classes to do just what you need.
Please see: https://stackoverflow.com/a/28268200/4517929
It seems to be by design (which I think we can all agree is lame). You'll probably have to resort to doing things in code for iPad landscape layout by checking something like
UIApplication.sharedApplication().statusBarOrientation.isLandscape
来源：https://stackoverflow.com/questions/24601468/ios-8-size-classes-for-ipad-landscape