How to mask UITableViewCells underneath a UITableView Transparent Header

Question

I want the header to mask the cells, but not the background.

I have a UITableView with transparent headers and cells similar to Apple\'s Notification Center (when yo

Answer 1

The Swift 3 version didn't work for me because I added the UITableViewController as a subview. So I had to make some changes in the extension of the scrollview.

This should also work with UITableViewController that have been pushed from another ViewController (Note: not tested)

extension NavNotitionTableViewController {
override func scrollViewDidScroll(_ scrollView: UIScrollView) {
    for cell in tableView.visibleCells {

        let calculatedY = cell.frame.origin.y - scrollView.contentOffset.y;
        if let customCell = cell as? NavNotitionTableViewCell {

            if(calculatedY < 44 && calculatedY > 0){
                let hideAmount = 44 - calculatedY;

                if let customCell = cell as? NavNotitionTableViewCell {
                    customCell.maskCell(fromTop: hideAmount)
                }
            }else if (calculatedY > 0){
                //All other cells
                customCell.maskCell(fromTop: 0)
            }else if (calculatedY < 0){
                customCell.maskCell(fromTop: cell.frame.height);
            }
        }
    }
}
}

In this example, I first get the frame Y origin of the cell and distract the scollViews contentOffsetY.

The height of my custom section is 44. So I define the hideAmount value for the mask.

The Cell functions are untouched:

public func maskCell(fromTop margin: CGFloat) {
    layer.mask = visibilityMask(withLocation: margin / frame.size.height)
    layer.masksToBounds = true
}

private func visibilityMask(withLocation location: CGFloat) -> CAGradientLayer {
    let mask = CAGradientLayer()
    mask.frame = bounds
    mask.colors = [UIColor.white.withAlphaComponent(0).cgColor, UIColor.white.cgColor]
    let num = location as NSNumber
    mask.locations = [num, num]
    return mask
}