I have this arrangement in Interface Builder, All properties are set to zero.
However, when I run it on both device and simulator it appears like this
Where is the space above the cells come from?
So I try to set these properties for UICollectionViewFlowLayout in code like this
UICollectionViewFlowLayout *layout = [[UICollectionViewFlowLayout alloc] init];
layout.headerReferenceSize = CGSizeZero;
layout.footerReferenceSize = CGSizeZero;
layout.sectionInset = UIEdgeInsetsMake(0, 0, 0, 0);
layout.minimumInteritemSpacing = 0;
layout.minimumLineSpacing = 0;
layout.itemSize = CGSizeMake(103, 119);
self.calendarView.collectionViewLayout = layout;
UICollectionView is descendant of UIScrollView class which has
contentInset property, setting -20 top inset fixes the problem
[self.calendarView setContentInset:UIEdgeInsetsMake(-20, 0, 0, 0)];
However, the problem comes from UIViewController's
Default value is YES, which allows the view controller to adjust its scroll view insets in response to the screen areas consumed by the status bar, navigation bar, and toolbar or tab bar. Set to NO if you want to manage scroll view inset adjustments yourself.
That's why we get adjusted content insets for status bar. It's better to disable automatically adjusting than manually set value which doesn't match in result picture.