UICollectionView animate individual items during transition

Question

Is it possible to animate each item individually in a UICollectionView when I transition to a child View Controller? I have a UICollectionViewController and when an item is selected I want all items surrounding that item to bounce away from the selected item.

Answer 1

What you describe sounds like a layoutTransition in your UICollectionView. My suggestion would be to create a new layout by subclassing UICollectionViewLayout and override

- (UICollectionViewLayoutAttributes *)layoutAttributesForItemAtIndexPath:(NSIndexPath *)indexPath

There you can modify the frames of your items to create the effect you are looking for. In particular, you could keep track of the indexPath that was selected and remain that item unaffected. For the rest you could do something like this:

CGRect selectedItemFrame = [[super layoutAttributesForItemAtIndexPath:self.selectedIndexPath] frame];

CGFloat xOffset = attributes.frame.origin.x <= selectedItemFrame.origin.x ? -400.0 : 400.0;
CGFloat yOffset = attributes.frame.origin.y <= selectedItemFrame.origin.y ? -600.0 : 600.0;
CGRect newFrame = CGRectOffset(attributes.frame, xOffset, yOffset);
attributes.frame = newFrame;

Then, just trigger the transition from one layout to the other.