How can I customize the selection state of my UICollectionViewCell subclass?

Question

I have a custom UICollectionViewCell subclass that overwrites initWithFrame: and layoutSubviews to setup its views. However, I\'m now trying to do two

Answer 1

Add a public method performSelectionAnimations to the definition of MyCollectionViewCell that changes the desired UIImageView and performs the desired animation. Then call it from collectionView:didSelectItemAtIndexPath:.

So in MyCollectionViewCell.m:

- (void)performSelectionAnimations {
    // Swap the UIImageView
    ...

    // Light bounce animation
    ...
}

And in your UICollectionViewController:

- (void)collectionView:(UICollectionView *)collectionView didSelectItemAtIndexPath:(NSIndexPath *)indexPath {
    MyCollectionViewCell *cell = (MyCollectionViewCell *)[collectionView cellForItemAtIndexPath:indexPath];
    [cell performSelectionAnimations];
}

Notice I've taken out the call to [cell setSelected:YES], since that should already be taken care of by the UICollectionView. From the documentation:

The preferred way to select the cell and highlight it is to use the selection methods of the collection view object.

Answer 2

In your custom UICollectionViewCell subclass, you can implement didSet on the isSelected property.

Swift 3:

override var isSelected: Bool {
    didSet {
        if isSelected {
            // animate selection
        } else {
            // animate deselection
        }
    }
}

Swift 2:

override var selected: Bool {
    didSet {
        if self.selected {
            // animate selection
        } else {
            // animate deselection
        }
    }
}

Answer 3

If you want to show animation on selection then following method might helpful to you :

 - (void)collectionView:(UICollectionView *)collectionView didSelectItemAtIndexPath:(NSIndexPath *)indexPath {
     NSLog(@"cell #%d was selected", indexPath.row);


     // animate the cell user tapped on
     UICollectionViewCell  *cell = [collectionView cellForItemAtIndexPath:indexPath];

     [UIView animateWithDuration:0.8
                           delay:0
                         options:(UIViewAnimationOptionAllowUserInteraction)
                      animations:^{
                          [cell setBackgroundColor:UIColorFromRGB(0x05668d)];
                      }
                      completion:^(BOOL finished){
                          [cell setBackgroundColor:[UIColor clearColor]];
                      }
      ];


 }

Answer 4

In your custom UICollectionViewCell subclass you could override the setSelected: as so:

- (void)setSelected:(BOOL)selected {
    [super setSelected:selected];

    if (selected) {
        [self animateSelection];
    } else {
        [self animateDeselection];
    }
}

I have found that on repeated touches this method is called on a cell even if it's already selected so you may want to just check that you are really changing state before firing unwanted animations.

Answer 5

Should not mess with state when overridden in this way:

override var isSelected: Bool {

    get {
        return super.isSelected
    }

    set {
        super.isSelected = newValue
        .
        .
        .
    }
}