Animate UICollectionViewCell on Tap

Question

I would like to start some animation on a UICollectionViewCell when the user taps on a cell. My idea was to select the corresponding cell in didSelectItemAtIndexPath and trigger an animation. However, this doesn't work:

- (void)collectionView:(UICollectionView *)collectionView didSelectItemAtIndexPath:(NSIndexPath *)indexPath
{
    // animate the cell user tapped on
    ProductCollectionViewCell* cell = [collectionView dequeueReusableCellWithReuseIdentifier:@"ProductReuseID" forIndexPath:indexPath];
    
    [UIView animateWithDuration:5.0
                          delay:0
                        options:(UIViewAnimationOptionAllowUserInteraction)
                     animations:^{
                         NSLog(@"animation start");
                         [cell.layer setBackgroundColor:[UIColor colorWithRed: 180.0/255.0 green: 238.0/255.0 blue:180.0/255.0 alpha: 1.0].CGColor];
                     }
                     completion:^(BOOL finished){
                         NSLog(@"animation end");
                         [cell.layer setBackgroundColor:[UIColor whiteColor].CGColor];
                     }
    ];
}

Actually, the animation starts and ends at the same time (although animateWithDuration is set to 5). Next attempt was to skip the animation and simply set for instance a different border style:

- (void)collectionView:(UICollectionView *)collectionView didSelectItemAtIndexPath:(NSIndexPath *)indexPath
{
    // animate the cell user tapped on
    ProductCollectionViewCell* cell = [collectionView dequeueReusableCellWithReuseIdentifier:@"ProductReuseID" forIndexPath:indexPath];
    
    [cell.layer setBorderWidth:5.0f];
}

However, this doesn't change anything (probably because I have to redraw the cell manually?).

Do you have any ideas how to animate a UICollectionViewCell when the user tapped on it?

Kind regards, Christian

Answer 1

It would appear that you are obtaining the wrong Cell. Sending the dequeueReusableCellWithReuseIdentifier:forIndexPath: message does not obtain the cell in use in the view at the indexPath in the second parameter, but dequeues a previously used but reusable cell; if no reusable cell is available, a new one is created. See Reference 1 below.

Replacing:

ProductCollectionViewCell* cell = [collectionView dequeueReusableCellWithReuseIdentifier:@"ProductReuseID" forIndexPath:indexPath];

With:

ProductCollectionViewCell* cell = [collectionView cellForItemAtIndexPath:indexPath];

In your code above, should give you the proper cell to work with.

Here is your fist example, rewritten.

- (void)collectionView:(UICollectionView *)collectionView didSelectItemAtIndexPath(NSIndexPath *)indexPath
{
    // animate the cell user tapped on
    UICollectionViewCell  *cell = [collectionView cellForItemAtIndexPath:indexPath];    
    [UIView animateWithDuration:5.0
            delay:0
            options:(UIViewAnimationOptionAllowUserInteraction)
                animations:^{
                    NSLog(@"animation start");
                    [cell setBackgroundColor:[UIColor colorWithRed: 180.0/255.0 green: 238.0/255.0 blue:180.0/255.0 alpha: 1.0]];
                }
                completion:^(BOOL finished){
                    NSLog(@"animation end");
                    [cell setBackgroundColor:[UIColor whiteColor]];
                }
    ];
}

References:

• http://developer.apple.com/library/ios/#documentation/UIKit/Reference/UICollectionView_class/Reference/Reference.html#//apple_ref/occ/cl/UICollectionView

Answer 2

You can customize the animation while select/tap the UICollectionViewCell with custom animation duration by following the code. So, You don't need to change the background color of it.

With following options - UIViewAnimationOption

• UIViewAnimationOptionCurveEaseIn
• UIViewAnimationOptionCurveEaseOut

• UIViewAnimationOptionAllowUserInteraction

  UICollectionViewDelegate - didSelectItemAtIndexPath method

  UICollectionViewCell *uviCollectionCell =  [collectionView cellForItemAtIndexPath:indexPath];
  
  [UIView animateWithDuration:0.4 delay:0 options:(UIViewAnimationOptionCurveEaseIn) animations:^{
          NSLog(@"animation start");
          CALayer *layer = uviCollectionCell.layer;
          CATransform3D rotationAndPerspectiveTransform = CATransform3DIdentity;
          rotationAndPerspectiveTransform = CATransform3DRotate(rotationAndPerspectiveTransform, 15.0f * M_PI / 180.0f, 1.0f, 0.0f, 0.0f);
          layer.transform = rotationAndPerspectiveTransform;
  } completion:^(BOOL finished) {
          [UIView animateWithDuration:0.3 delay:0 options:(UIViewAnimationOptionCurveEaseOut) animations:^{
              NSLog(@"animation end");
              CALayer *layer = uviCollectionCell.layer;
              CATransform3D rotationAndPerspectiveTransform = CATransform3DIdentity;
              rotationAndPerspectiveTransform.m24 = 0;
              rotationAndPerspectiveTransform =CATransform3DRotate(rotationAndPerspectiveTransform, 0.0f * M_PI / 180.0f, 1.0f, 0.0f, 0.0f);
              layer.transform = rotationAndPerspectiveTransform;
          } completion:nil];
      }
  ];