Handling interface rotation in iOS 7

Question

Very simple question, but I'm asking as there seems to be a lot of conflicting views and I've been completely unable to find a definitive answer, let alone a modern one.

I use Auto Layout for 99% of my handling of the user changing from portrait to landscape or vice-versa in a UIViewController. Works great. But sometimes, I have to rely on frames still for one reason or another.

How would I best handle this?

You have willAnimateRotationToInterfaceOrientation, willRotateToInterfaceOrientation, the NSNotification methods with checking status bar, and I'm sure there's some others.

If I want to change the position of a view when the user rotates, which method should I be changing the frame in? And is it best to do it with a simple setFrame: or should I be using autoresizing masks?

Answer 1

Since iOS6, you should not be using willRotateToInterfaceOrientation: and didRotateFromInterfaceOrientation:. These are only called on the front-most presented view controller, and will not be called on others. This means if you have a pushed view controller or a presented view controller, all others will not layout correctly.

Instead, you should always use viewWillLayout and viewDidLayout to handle rotation. They are both called inside an animation block, so anything you do which is animatable, will be animated.

For positioning views, you can either set the frames yourself, or use auto-layout constraints and adjust the constraints in viewDidLayout. If you go the auto-layout route, never remove and add constraints. Use the same constraints as much as possible and just adjust their constant values.

Answer 2

When I'm changing the main view frame, I typically adjust the frame in willRotateToInterfaceOrientation if I need to. Then I adjust any subviews by overriding layoutSubviews for my main view.

I don't know that this is a definitive answer, though - I don't think there really is a definitive answer - it depends on how your application is structured.

wilLRotateToInterfaceOrientation and didRotateFromInterfaceOrientation are best used for stuff you need to do before and after rotation, respectively (for example, disabling user interaction before the rotation begins, and reenabling it after). Everything else should be done in layoutSubviews if possible.

Autoresizing masks are useful sometimes, but I usually lay everything out manually to avoid any surprises when things change between iOS releases (as they often do).