Animation Duration for UICollectionView selectItemAtIndexPath:animated:scrollPosition:

Question

I have tried to set the duration (with the normal methods that I would try) for setting the animation duration for UICollectionView's selectItemAtIndexPath:animated:scrollPosition: method (or the scrollToItemAtIndexPath:atScrollPosition:animated: method). I've tried [UIView setAnimationDuration], and I've tried wrapping it in a CATransaction. I've been unsuccessful up to this point at changing that animation duration (although I admit that I could have made a mistake in this logic).

Thoughts?

UPDATE:

I have tried a good number of approaches here. The closest solution is to do what we would normally do for UIScrollView animation (by setting the animated: argument to NO and wrapping it in a UIView animation block). This works perfectly fine for the scrollview. However, this screws with the UICollectionView creation process for some reason.

I have included an example below using two approaches. Each approach assumes that you have 4 sections with 4 items in each section. In addition, the animation assumes you are moving from 0,0 to 3,3.

Using Default Animation

Part of the issue here certainly seems tied to UICollectionView. If you take the following approach (using the default animation option) - all works fine:

[self.collectionView scrollToItemAtIndexPath:[NSIndexPath indexPathForItem:3 inSection:3]                                 atScrollPosition:UICollectionViewScrollPositionCenteredHorizontally                                         animated:YES]; 

When this is being executed, each cell in-between the current visible cells and the destination cell is created. I have included logging on the collectionView:cellForItemAtIndexPath: method:

2013-05-18 09:33:24.366 DEF-CV-Testing[75463:c07] Transition Cell Created for Index Path: <NSIndexPath 0x8913f40> 2 indexes [0, 1] Cell Created for Index Path: <NSIndexPath 0x75112e0> 2 indexes [0, 2] Cell Created for Index Path: <NSIndexPath 0xfe1a6c0> 2 indexes [0, 3] Cell Created for Index Path: <NSIndexPath 0x89159e0> 2 indexes [1, 0] Cell Created for Index Path: <NSIndexPath 0x8a10e70> 2 indexes [1, 1] Cell Created for Index Path: <NSIndexPath 0x7510d90> 2 indexes [1, 2] Cell Created for Index Path: <NSIndexPath 0x75112a0> 2 indexes [1, 3] Cell Created for Index Path: <NSIndexPath 0x8915a00> 2 indexes [2, 0] Cell Created for Index Path: <NSIndexPath 0x75111c0> 2 indexes [2, 1] Cell Created for Index Path: <NSIndexPath 0xfe17f30> 2 indexes [2, 2] Cell Created for Index Path: <NSIndexPath 0xfe190c0> 2 indexes [2, 3] Cell Created for Index Path: <NSIndexPath 0xfe16920> 2 indexes [3, 0] Cell Created for Index Path: <NSIndexPath 0x75112a0> 2 indexes [3, 1] Cell Created for Index Path: <NSIndexPath 0xfe1a4f0> 2 indexes [3, 2] Cell Created for Index Path: <NSIndexPath 0x75142d0> 2 indexes [3, 3] 

Using Custom Animation

When wrapping the scrollToItemAtIndexPath: method in a UIView animation block, items are not created correctly. See code sample here:

[UIView animateWithDuration:5.0 delay:0.0 options:0 animations:^{     [self.collectionView scrollToItemAtIndexPath:[NSIndexPath indexPathForItem:3 inSection:3]                                 atScrollPosition:UICollectionViewScrollPositionCenteredHorizontally                                         animated:NO]; } completion:^(BOOL finished) {     NSLog(@"Completed"); }]; 

The currently visible cells disappear and only the destination one is created. I have included the same logging on the collectionView:cellForItemAtIndexPath: method:

Transition Cell Created for Index Path: <NSIndexPath 0x71702f0> 2 indexes [3, 3] Completed 

Answer 1

I had similar problems with UITableView which I solved by the following code:

[CATransaction begin]; [CATransaction setCompletionBlock:onCompletion]; [CATransaction setAnimationDuration:duration];  [self.collectionView scrollToItemAtIndexPath:[NSIndexPath indexPathForItem:3 inSection:3]                             atScrollPosition:UICollectionViewScrollPositionCenteredHorizontally                                     animated:YES];  [CATransaction commit]; 

Obviously, you can't call it with animated:NO because the animation code inside the method is important. Using a CATransaction to wrap the animation worked for me.