uicollectionview decoration broken frame?

Question

I have a UICollectionView with custom layout and try to display a decoration view.

The problem illustrated with some code:

attributeDecorationTime.frame = CGRectMake(0.0f,
                                           0.0f,
                                           [self getXOffset],
                                           (epgCollectionView.bounds.size.height+epgCollectionView.contentOffset.y));

This code is supposed to display a decoration view that split the screen in two part if [self getXOffest] value is on the center of the screen. The left part is the decoration view and on the right side we can see the half collectionview that is not hidden by the decoration view.

On iphone simulator, at start, it's working as expected but when i begin to scroll down a bit, i can see the bottom of the decoration view. I don't want to ee the bottom of the decoration view, the decoration view must always cover the screen height.

It looks like if i make the epgCollectionView.contentOffset.y*2, it works, maybe retina screen related ? But why does it cover the screen at that if it's a retina @2x pixels problem ???

Now if i use this code:

attributeDecorationTime.frame = CGRectMake(0.0f,
                                           epgCollectionView.contentOffset.y,
                                           [self getNowXOffset],
                                           (epgCollectionView.bounds.size.height+epgCollectionView.contentOffset.y));

The decoration view scroll down when i scroll the collection view down.

When i understand correctly what it means, decoration view don't use the same x y as regular cells or header cells.

Now, when i run the first code on ipad simulator, the decoration view that should be on y=0 start at y=74 which is the collection view y position in the main view controller.

Can someone explain me what i'm doing wrong ???

I just want a decoration view that cover the full height of the screen on iphone/ipad.

On a side not, i don't have any problem with the x value which is the width of the decoration view. This make me think, should i invalidate the view when i change the attributes ? The custom layout recalculate the attributes on every scroll. And [self invalidateLayout] in the custom layout doesn't seem to change anything.

Answer 1

Have you tried

attributeDecorationTime.frame = CGRectMake(0.0f,
                                       0.0f,
                                       [self getXOffset],
                                       (epgCollectionView.contentSize.height));

I think you should use contentSize.height to cover full content height instead of screen height. In a scrollable view like UICollectionView the contentSize is usually larger than screen size