Animations during pushing view controllers to nav. controller sometimes stop working - iphone

Question

I use this standard code many times in my app to push VCs to nav. controller.
[self.navigationController pushViewController:detailController animated:YES];
But sometimes they stop working- view controller is pushed correcty but without animation (just as i would use "animated:NO") , and i cant figure out why.
Any suggestion what to observe or try?

Answer 1

Whenever you use ...animated:YES/NO the Cocoa framework will determine if it can/can not do it and more often than not it just fails. Like Michael said, you might not be on the main thread or who knows what. If you look at the latest Lion API's for fullscreen animation on an NSWindow you will find various delegates for the animation failing providing details. So I wouldn't expect Apple to go back with an animator and add such functionality.
To answer your question, primarily I would use my own custom animations using Core Animations. They really are not that bad. To get you started, you can create a Category or Class Method for convenience like this:
+ (void) animateWithDuration:(NSTimeInterval)duration
animation:(void(^)())animationBlock
completion:(void(^)())completionBlock {
[NSAnimationContext runAnimationGroup:^( NSAnimationContext *context ) {
if ( duration > 0 ) [context setDuration:duration];
[context setTimingFunction:[CAMediaTimingFunction functionWithName:kCAMediaTimingFunctionDefault]];
if ( animationBlock ) animationBlock();
} completionHandler:^ {
if ( completionBlock ) completionBlock();
}];
}
You can then use it like so for several animations. Like so...
[AnimationContext animateWithDuration:myDuration animation:^{
// You can use whatever animation you want here or even nest
CABasicAnimation *fade = /* opacity animation */;
[view.layer addAnimation:fade forKey:nil];
} completion:^{
// Do some completion here.
}];
One note, you have more control over your animations this way.
Hope this answers what you are looking for.
(Huge Note, my example is for Mac OS X. On iOS the equivalent to NSAnimationContext is to wrap using CATransaction)