iosswiftuitableviewuiviewuikit

How to add UIView above a tableView Swift(iOS)

I'm trying to add a UIview above the tableView but my view is hiding behind the cells. The view should half on footer of section 0 and half on header of section 1, The empty space is tha padding for header.

enter image description here

I have used bringSubviewToFront method but it's not working. Everything that I had tried are commented below.

    func setupMyRankView(){
//        tableView.addSubview(myRankView)

//      tableView.footerView(forSection: 0)?.insertSubview(myRankView, aboveSubview: self.view)
//        tableView.footerView(forSection: 0)?.bringSubviewToFront(myRankView)
                self.view.bringSubviewToFront(myRankView)
//        tableView.cellForRow(at: indexPath)?.insertSubview(myRankView, aboveSubview: self.view)
//        tableView.cellForRow(at: indexPath)?.bringSubviewToFront(myRankView)
        
       myRankView.myRankLabel.text = "Hello"
       
    }
Solution

  • As the table view manages its cells and section headers/footers, it is constantly rearranging the z-orders.

    What you need to do is bring the "rank" views to the front every time the table updates itself.

    One way to do that is by implementing the table view's scrollViewDidScroll -- this gives you the added advantage of being a good place to calculate the frame(s) for the "rank" view(s).

    It will go something like this:

    and the code will look like this:

        // for each of the "rank" views
    for (i, v) in rankViews.enumerated() {
        // get the rect for the section footer
        var r1 = tableView.rectForFooter(inSection: i)
        // get the rect for the NEXT section header
        let r2 = tableView.rectForHeader(inSection: i + 1)
        
        // set the full rect size to the
        //  Bottom of the Header minus the Top of the Footer
        r1.size.height = r2.maxY - r1.minY
        
        // start with setting the frame of the "rank" view to 50x50
        v.frame = CGRect(x: 0.0, y: 0.0, width: 50.0, height: 50.0)
        // center it horizontonally and vertically
        v.center = CGPoint(x: r1.midX, y: r1.midY)
        
        // bring it to the front
        tableView.bringSubviewToFront(v)
    }

    Here's a complete example you can try out...

    Sample "Rank" view

    class MyRankView: UIView {
    
    let myRankLabel = UILabel()
    override init(frame: CGRect) {
        super.init(frame: frame)
        commonInit()
    }
    required init?(coder: NSCoder) {
        super.init(coder: coder)
        commonInit()
    }
    func commonInit() {
        myRankLabel.textAlignment = .center
        myRankLabel.translatesAutoresizingMaskIntoConstraints = false
        addSubview(myRankLabel)
        let g = self
        NSLayoutConstraint.activate([
            myRankLabel.topAnchor.constraint(equalTo: g.topAnchor, constant: 0.0),
            myRankLabel.leadingAnchor.constraint(equalTo: g.leadingAnchor, constant: 0.0),
            myRankLabel.trailingAnchor.constraint(equalTo: g.trailingAnchor, constant: 0.0),
            myRankLabel.bottomAnchor.constraint(equalTo: g.bottomAnchor, constant: 0.0),
        ])
        layer.borderColor = UIColor.systemGreen.cgColor
        layer.borderWidth = 2
        myRankLabel.textColor = .systemGreen
        backgroundColor = .white
    }

    override func layoutSubviews() {
        super.layoutSubviews()
        layer.cornerRadius = min(bounds.width, bounds.height) * 0.5
    }
}

    Simple multi-line label cell

    class MyTestCell: UITableViewCell {
    
    let theLabel: UILabel = {
        let v = UILabel()
        v.numberOfLines = 0
        return v
    }()
    
    override init(style: UITableViewCell.CellStyle, reuseIdentifier: String?) {
        super.init(style: style, reuseIdentifier: reuseIdentifier)
        commonInit()
    }
    required init?(coder: NSCoder) {
        super.init(coder: coder)
        commonInit()
    }
    func commonInit() -> Void {
        theLabel.translatesAutoresizingMaskIntoConstraints = false
        contentView.addSubview(theLabel)
        let g = contentView.layoutMarginsGuide
        NSLayoutConstraint.activate([
            theLabel.topAnchor.constraint(equalTo: g.topAnchor),
            theLabel.leadingAnchor.constraint(equalTo: g.leadingAnchor),
            theLabel.trailingAnchor.constraint(equalTo: g.trailingAnchor),
            theLabel.bottomAnchor.constraint(equalTo: g.bottomAnchor),
        ])
        theLabel.backgroundColor = .yellow
    }
    
}

    Reusable section header/footer views

    class MyHeaderFooterBaseView: UITableViewHeaderFooterView {
    
    let label = UILabel()
    override init(reuseIdentifier: String?) {
        super.init(reuseIdentifier: reuseIdentifier)
        commonInit()
    }
    required init?(coder: NSCoder) {
        super.init(coder: coder)
        commonInit()
    }
    func commonInit() {
        label.translatesAutoresizingMaskIntoConstraints = false
        addSubview(label)
        let g = self.layoutMarginsGuide
        NSLayoutConstraint.activate([
            label.topAnchor.constraint(equalTo: g.topAnchor, constant: 8.0),
            label.leadingAnchor.constraint(equalTo: g.leadingAnchor, constant: 0.0),
            label.trailingAnchor.constraint(equalTo: g.trailingAnchor, constant: 0.0),
            label.bottomAnchor.constraint(equalTo: g.bottomAnchor, constant: -8.0),
        ])
        backgroundView = UIView()
    }
}

class MyHeaderView: MyHeaderFooterBaseView {
    override func commonInit() {
        super.commonInit()
        label.textAlignment = .center
        backgroundView?.backgroundColor = .cyan
    }
}

class MyFooterView: MyHeaderFooterBaseView {
    override func commonInit() {
        super.commonInit()
        label.textAlignment = .left
        backgroundView?.backgroundColor = UIColor(white: 0.9, alpha: 1.0)
    }
}

    Sample controller

    class ViewController: UIViewController, UITableViewDataSource, UITableViewDelegate {

    let tableView = UITableView(frame: .zero, style: .grouped)
    
    // we'll use varying
    //  number of rows per section and
    //  number of lines per row
    let myData: [[Int]] = [
        [1, 2, 3, 4],
        [3, 2, 1],
        [2, 1, 4, 3, 1],
        [2, 2, 2, 3],
        [1, 1, 5, 1],
        [2, 2, 2],
    ]
    
    var rankViews: [MyRankView] = []
    
    override func viewDidLoad() {
        super.viewDidLoad()

        view.backgroundColor = .systemYellow
        
        tableView.translatesAutoresizingMaskIntoConstraints = false
        view.addSubview(tableView)
        
        let g = view.safeAreaLayoutGuide
        
        NSLayoutConstraint.activate([
            
            tableView.topAnchor.constraint(equalTo: g.topAnchor, constant: 20.0),
            tableView.leadingAnchor.constraint(equalTo: g.leadingAnchor, constant: 20.0),
            tableView.trailingAnchor.constraint(equalTo: g.trailingAnchor, constant: -20.0),
            tableView.bottomAnchor.constraint(equalTo: g.bottomAnchor, constant: -20.0),
            
        ])
        
        tableView.register(MyTestCell.self, forCellReuseIdentifier: "c")
        tableView.register(MyHeaderView.self, forHeaderFooterViewReuseIdentifier: "h")
        tableView.register(MyFooterView.self, forHeaderFooterViewReuseIdentifier: "f")
        
        tableView.dataSource = self
        tableView.delegate = self
        
        tableView.sectionHeaderTopPadding = 20.0
        tableView.estimatedSectionHeaderHeight = 60.0
        tableView.estimatedSectionFooterHeight = 60.0
        
        for i in 0..<myData.count - 1 {
            let v = MyRankView()
            v.myRankLabel.text = "\(i)"
            tableView.addSubview(v)
            rankViews.append(v)
        }

    }

    override func viewDidAppear(_ animated: Bool) {
        super.viewDidAppear(animated)
        updateRankViews()
    }
    func numberOfSections(in tableView: UITableView) -> Int {
        return myData.count
    }
    func tableView(_ tableView: UITableView, numberOfRowsInSection section: Int) -> Int {
        return myData[section].count
    }
    func tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell {
        let c = tableView.dequeueReusableCell(withIdentifier: "c", for: indexPath) as! MyTestCell
        var s: String = "\(indexPath)"
        for i in 2..<(myData[indexPath.section][indexPath.row] + 1) {
            s += "\nLine \(i)"
        }
        c.theLabel.text = s
        return c
    }
    func tableView(_ tableView: UITableView, viewForHeaderInSection section: Int) -> UIView? {
        let v = tableView.dequeueReusableHeaderFooterView(withIdentifier: "h") as! MyHeaderView
        v.label.text = "Section Header: \(section)"
        return v
    }
    func tableView(_ tableView: UITableView, viewForFooterInSection section: Int) -> UIView? {
        let v = tableView.dequeueReusableHeaderFooterView(withIdentifier: "f") as! MyFooterView
        v.label.text = "Section Footer: \(section)"
        return v
    }
    
    func scrollViewDidScroll(_ scrollView: UIScrollView) {
        updateRankViews()
    }
    func updateRankViews() {
        
        // for each of the "rank" views
        for (i, v) in rankViews.enumerated() {
            // get the rect for the section footer
            var r1 = tableView.rectForFooter(inSection: i)
            // get the rect for the NEXT section header
            let r2 = tableView.rectForHeader(inSection: i + 1)
            
            // set the full rect size to the
            //  Bottom of the Header minus the Top of the Footer
            r1.size.height = r2.maxY - r1.minY
            
            // start with setting the frame of the "rank" view to 50x50
            v.frame = CGRect(x: 0.0, y: 0.0, width: 50.0, height: 50.0)
            // center it horizontonally and vertically
            v.center = CGPoint(x: r1.midX, y: r1.midY)
            
            // bring it to the front
            tableView.bringSubviewToFront(v)
        }
        
    }
}

    and it looks like this when running:

    enter image description here enter image description here