how to have UITableView's pinned headers hide after scrolling - swift

Question

I want to have my tableViewHeaders visible as the user scrolls by pinning to the top which is the current behaviour in my tableView. However, when the tableView stops scrolling, I want to remove these 'pinned' headers. I am achieving this in my collectionView project using the following in my scrollView delegate methods:
if let cvl = chatCollectionView.collectionViewLayout as? UICollectionViewFlowLayout {
cvl.sectionHeadersPinToVisibleBounds = false
cvl.invalidateLayout()
}
Is there a similar way to hide a tableView's 'pinned' (sticky) headers? I am using a tableViewController.

Answer 1

This is my solution to this issue. I wonder if there is a simpler way to do this though.
Please note, this will only work if your header is a UITableViewHeaderFooterView. Not if you are using a UITableViewCell for a header. If you are using a UITableViewCell, tableView.headerView(forSection: indexPathForVisibleRow.section) will return nil.
In order to hide the pinned headers when the tableView stops scrolling and have them re-appear when the tableView starts scrolling again, override these four scrollView delegate methods.
In the first two (scrollViewWillBeginDragging and scrollViewWillBeginDecelerating), get the section header for the first section of the visible rows and make sure it is not hidden.
In the second two delegate methods, do a check to see that for each of the visible rows, the header frame for that row is not overlapping the frame for the row cell. If it is, then this is a pinned header and we hide it after a delay. We need to ensure that the scrollView is not still dragging before removing the pinned header as will be the case when the user lifts their finger but the scroll view continues to scroll. Also because of the time delay, we check that the scrollView is not dragging before removing it in case the user starts scrolling again less than 0.5 seconds after the scroll stops.
override func scrollViewWillBeginDragging(_ scrollView: UIScrollView) {
showPinnedHeaders()
}
override func scrollViewWillBeginDecelerating(_ scrollView: UIScrollView) {
showPinnedHeaders()
}
override func scrollViewDidEndDecelerating(_ scrollView: UIScrollView) {
removePinnedHeaders()
}
override func scrollViewDidEndDragging(_ scrollView: UIScrollView, willDecelerate decelerate: Bool) {
removePinnedHeaders()
}
private func showPinnedHeaders() {
for section in 0..<totalNumberOfSectionsInYourTableView {
tableView.headerView(forSection: section)?.isHidden = false
}
}
private func removePinnedHeaders() {
if let indexPathsForVisibleRows = tableView.indexPathsForVisibleRows {
if indexPathsForVisibleRows.count > 0 {
for indexPathForVisibleRow in indexPathsForVisibleRows {
if let header = tableView.headerView(forSection: indexPathForVisibleRow.section) {
if let cell = tableView.cellForRow(at: indexPathForVisibleRow) {
if header.frame.intersects(cell.frame) {
let seconds = 0.5
let delay = seconds * Double(NSEC_PER_SEC)
let dispatchTime = DispatchTime.now() + Double(Int64(delay)) / Double(NSEC_PER_SEC)
DispatchQueue.main.asyncAfter(deadline: dispatchTime, execute: {
if !self.tableView.isDragging && header.frame.intersects(cell.frame) {
header.isHidden = true
}
})
}
}
}
}
}
}
}
Additionally add removePinnedHeaders() to viewDidAppear() and any other rotation or keyboard frame change methods that will scroll your tableView.