iOS10 - ContentView Blocking Touches of UIButton in UITableView Header

Question

I am in the process of updating my app to iOS10 with Swift 2.3 and Xcode 8 Beta 1 and I have found that there is a UITableViewHeaderFooterContentView which is blocking touches to the UIButton on my subclass of UITableViewHeaderFooterView.

On the Xcode 8 Beta 1 simulator the UIButton works on iOS9.3 but not iOS10.

1) Is there any documentation for this?

2) How can I ensure my UI elements are on top of the new Content View in iOS10? (or allow touches through the UITableHeaderFooterContentView)

Thanks!

Table Header

import UIKit

class TableHeader: UITableViewHeaderFooterView {

    @IBOutlet weak var dayLabel: UILabel!

    @IBOutlet weak var dateLabel: UILabel!

    @IBOutlet weak var addNewEventButton: UIButton!

}

Code In View Controller dateCell.addNewEventButton is the UIButton that is no longer receiving touches in iOS10

func tableView(tableView: UITableView, viewForHeaderInSection section: Int) -> UIView? {


    let tintColor = TintManager().getTintColour()

    let dateCell:TableHeader = tableView.dequeueReusableHeaderFooterViewWithIdentifier("TableHeader") as! TableHeader

    //dateCell.bringSubviewToFront(dateCell.addNewEventButton)

    dateCell.dayLabel.text = Dates.day.uppercaseString

    dateCell.dateLabel.text = Dates.date

        dateCell.backgroundView = UIView(frame: dateCell.frame)
        dateCell.backgroundView!.backgroundColor = tintColor
        dateCell.dayLabel.textColor = UIColor.whiteColor()
        dateCell.dateLabel.textColor = UIColor.whiteColor()
        dateCell.addNewEventButton.backgroundColor = tintColor



    dateCell.addNewEventButton.tag = section
    dateCell.addNewEventButton.layer.cornerRadius = 20.0

    if (savedEventView.superview === self.view) {
        dateCell.addNewEventButton.removeTarget(nil, action: nil, forControlEvents: .AllEvents)
        dateCell.addNewEventButton.addTarget(self, action: #selector(ViewController.userPressedAddButtonToInsertSavedEvent(_:)), forControlEvents:.TouchUpInside)
    } else {
        dateCell.addNewEventButton.removeTarget(nil, action: nil, forControlEvents: .AllEvents)
        dateCell.addNewEventButton.addTarget(self, action: #selector(ViewController.userPressedAddNewEventOnTableViewHeader(_:)), forControlEvents:.TouchUpInside)
    }

    return dateCell
}

Answer 1

The offending view is in fact the contentView of the UITableViewHeaderFooterView (see the Apple Docs). So you should be able just to use sendSubview(toBack:) in order to stop it interfering with touches.

However, it seems that under iOS9 the UITableViewHeaderFooterView fails to correctly initialise the contentView if the view is loaded from a NIB. Although the contentView property is not optional, it is in fact nil, and you get a BAD ACCESS error if you try to access it. Nor can you set a value for contentView (either in code or as an outlet in IB) because it's a read only property (*). So the only solution I can think of is to use #available to conditionally include code to move the contentView to the back, if you are running on iOS 10 or newer. I would put the relevant code into your subclass:

override func awakeFromNib() {
    if #available(iOS 10, *) {
        self.sendSubview(toBack: contentView)
    }
}

(*) Indulging in wild speculation, my guess is that Apple based the UITableViewHeaderFooterView code heavily on UITableViewCell. Since IB has UITableViewCells in its object library (and notice these include the cell's contentView), it can ensure that the cell's contentView is correctly instantiated. But since there is no UITableViewHeaderFooterView in the object library, there's no way to get the contentView loaded correctly. Looks like they fixed it in iOS10 by instantiating an empty contentView. Pity they didn't also add UITableViewHeaderFooterView to the library.