When adding/removing/reloading cells in a UICollectionView using the FlowLayout the cells fade in/out. When doing things like updating a progress bar you get a lot of annoying flashing because of this, this category will prevent that. As an added benefit rotation animations will now show the cells moving into position.

UICollectionViewFlowLayout+NoFade.m

//
//  UICollectionViewFlowLayout+NoFade.m
//
//  Created by Rob Booth on 3/4/14.

#import "UICollectionViewFlowLayout+NoFade.h"
#import <objc/runtime.h>

@implementation UICollectionViewFlowLayout (NoFade)

+ (void) load
{
	Method original, swizzled;

	original = class_getInstanceMethod(self, @selector(initialLayoutAttributesForAppearingItemAtIndexPath:));
	swizzled = class_getInstanceMethod(self, @selector(noFadeInitialLayoutAttributesForAppearingItemAtIndexPath:));

	method_exchangeImplementations(original, swizzled);

	original = class_getInstanceMethod(self, @selector(finalLayoutAttributesForDisappearingItemAtIndexPath:));
	swizzled = class_getInstanceMethod(self, @selector(noFadeFinalLayoutAttributesForDisappearingItemAtIndexPath:));

	method_exchangeImplementations(original, swizzled);
}

- (UICollectionViewLayoutAttributes *)noFadeInitialLayoutAttributesForAppearingItemAtIndexPath:(NSIndexPath *)itemIndexPath
{
	// Not recursive, due to method exhange in load above
	// This is because we can't call super in a catagory
	UICollectionViewLayoutAttributes * attributes = [self noFadeInitialLayoutAttributesForAppearingItemAtIndexPath:itemIndexPath];

	attributes.alpha = 1.0;

	return attributes;
}

- (UICollectionViewLayoutAttributes *)noFadeFinalLayoutAttributesForDisappearingItemAtIndexPath:(NSIndexPath *)itemIndexPath
{
	// Not recursive, due to method exhange in load above
	// This is because we can't call super in a catagory
	UICollectionViewLayoutAttributes * attributes = [self noFadeFinalLayoutAttributesForDisappearingItemAtIndexPath:itemIndexPath];

	attributes.alpha = 1.0;

	return attributes;
}

@end

Thank you, @tooolbox!