Animated custom layout in UICollectionView - ios

Question

I need to create a UICollectionView like the following picture.
I have been able to make horizontally scrollable, but unable to make the UI like the picture. Any help? Thanks.

Answer 1

Here is what you wanted,you just need to have a custom UICollectionViewFlowLayout,and override the method -(NSArray<UICollectionViewLayoutAttributes *> *)layoutAttributesForElementsInRect:(CGRect)rect to change the cell display attributes.
Here is the layout code with comment in each main operation
#implementation HorizonSclaeLayout
-(instancetype)init{
self = [super init];
if (self) {
self.scrollDirection = UICollectionViewScrollDirectionHorizontal;
}
return self;
}
static const CGFloat kMaxDistancePercentage = 0.3f;
static const CGFloat kMaxRotation = 0;//(CGFloat)(70.0 * (M_PI / 180.0));
static const CGFloat kMaxZoom = 0.6f;
-(NSArray<UICollectionViewLayoutAttributes *> *)layoutAttributesForElementsInRect:(CGRect)rect{
//1 the visible rectangle of the collection view, calculated using the content offset of the view and the bounds size.
CGRect visibleRect = (CGRect){
.origin = self.collectionView.contentOffset,
.size = self.collectionView.bounds.size
};
//2 the maximum distance away from the center, which defines the distance from the center at which each cell is fully rotated
CGFloat maxDistance = visibleRect.size.width/2;
NSArray *array = [super layoutAttributesForElementsInRect:rect];
for (UICollectionViewLayoutAttributes *attributes in array) {
//3 find the distance of the cell from the center of the current visible rectangle
CGFloat distance = CGRectGetMidX(visibleRect) - attributes.center.x;
//4 normalize this distance against the maximum distance to give a percentage of how far the view is along the line from the center to the maximum points in either direction
CGFloat normalizedDistance = distance / maxDistance;
normalizedDistance = MIN(normalizedDistance, 1.0f);
normalizedDistance = MAX(normalizedDistance, -1.0f);
//5 calculate the rotation and zoom
CGFloat rotation = normalizedDistance * kMaxRotation;
CGFloat zoom = 1.0f + ((1.0f - ABS(normalizedDistance))*kMaxZoom);
//6 create the required transform by first setting m34 so that when the rotation is done
// skew is applied to make it have the appearance of coming out of and going into the screen
CATransform3D transform = CATransform3DIdentity;
transform.m34 = - 1.0 / 550.0;
transform = CATransform3DRotate(transform, rotation, 0.0f, 1.0f, 0.0f);
transform = CATransform3DScale(transform, zoom, zoom, 0.0f);
attributes.transform3D = transform;
}
return array;
}
-(CGSize)itemSize{
return CGSizeMake(60, 60 * 1.2);
}
-(CGFloat)minimumLineSpacing{
return 30;
}
-(BOOL)shouldInvalidateLayoutForBoundsChange:(CGRect)newBounds{
return YES;
}
#end

Answer 2

Here in this sample LineLayout has already implemented the required custom layout (that's what I guessed from the image shown).