Cross-fade certain UIViews on device orientation change

Question

I've got a bit of a query on how certain views rotate when an iOS device changes orientation.

I'm developing an app right now, and it basically consists of 2 view controllers: the first being a UITableViewController embedded in a UINavigationController, the second being a completely custom one being built on a stock standard UIViewController.

I've noticed that on my UINavigationController view, when the device rotates, the UINavigationBar and the UIToolbar both perform a cross-fade animation when transitioning to their landscape dimensions.

For technical reasons, I didn't use a UINavigationController for my custom view controller, but I manually added a UINavigationBar and a UIToolbar in the same places to it (Basically because I need those elements to be able to be overlaid on top of the background view, as they can optionally be hidden and I wanted direct control to do that).

However, when I rotate my device when my custom view controller is visible, the two bars do NOT perform a cross-fade transition. Instead, all of the subviews slide around (looking a bit chaotic), and the background image distorts as it immediately gets swapped over to the iPhone landscape version before the animation actually starts (ie, so it starts off tiling the 32pt high artwork inside a 44pt high UIToolbar).

I was just wondering, does anyone now how Apple actually goes about creating this cross-fade blending effect for certain UIViews when the device orientation changes?

Answer 1

Don't use native auto-rotation rotate your view. Rotate them manually. Look the second answer here:http://stackoverflow.com/questions/1220580/iphone-dev-manually-rotate-view . Essentially you sign up for device rotation notification and do the view rotations yourself.

If you want to crossfade the two views in addition to the UIView animate block specified in the link above go:

[UIView transitionWithView:superViewOfButtonView duration:2.0 options:UIViewAnimationOptionTransitionCrossDissolve animations:^{
    [thebuttonViewIWantToCrossFade setFrame:newPositionRect];
}completion:^(BOOL finished){
    //any completion code   
}];

Let me know if this works for you!

Answer 2

I actually came back and re-explored this. While the UIView and CAAnimation transition methods do indeed work, their respective framerates on different iOS devices vary so wildly that I didn't think implementing them was the best solution.

I finally bit the bullet and contacted Apple Developer Relations and asked them directly (If you didn't know, each Mac/iOS developer may ask 2 questions to these guys for free each year!).

They replied promptly, and informed me that several Apple engineers actually presented a talk on that exact topic at WWDC 2012.

The talk was recorded, and is available to registered Apple developers on iTunes under the title "Polishing Your Interface Rotations". It covers many different methods on handling interface orientation and is really worth watching. :)

Hope this also helps!