Using ScrollView Programmatically in Swift 3

Question

I have searched other questions and seem to still have some trouble creating my scrollView programmatically with autolayout in swift 3. I am able to get my scrollview to show up as shown in the picture below, but when I scroll to the bottom my other label does not show up and the 'scroll top' label does not disappear.

Hoping someone can help review my code below!

import UIKit

class ViewController: UIViewController {

let labelOne: UILabel = {
    let label = UILabel()
    label.text = "Scroll Top"
    label.backgroundColor = .red
    label.translatesAutoresizingMaskIntoConstraints = false
    return label
}()

let labelTwo: UILabel = {
    let label = UILabel()
    label.text = "Scroll Bottom"
    label.backgroundColor = .green
    label.translatesAutoresizingMaskIntoConstraints = false
    return label
}()


override func viewDidLoad() {
    super.viewDidLoad()

    let screensize: CGRect = UIScreen.main.bounds
    let screenWidth = screensize.width
    let screenHeight = screensize.height
    var scrollView: UIScrollView!
    scrollView = UIScrollView(frame: CGRect(x: 0, y: 120, width: screenWidth, height: screenHeight))
    scrollView.contentSize = CGSize(width: screenWidth, height: 2000)
    scrollView.addSubview(labelOne)
    scrollView.addSubview(labelTwo)


    view.addSubview(labelOne)
    view.addSubview(labelTwo)
    view.addSubview(scrollView)

    // Visual Format Constraints
    view.addConstraints(NSLayoutConstraint.constraints(withVisualFormat: "H:|[v0]|", options: NSLayoutFormatOptions(), metrics: nil, views: ["v0": labelOne]))
    view.addConstraints(NSLayoutConstraint.constraints(withVisualFormat: "V:|-100-[v0]", options: NSLayoutFormatOptions(), metrics: nil, views: ["v0": labelOne]))

    // Using iOS 9 Constraints in order to place the label past the iPhone 7 view
    view.addConstraint(NSLayoutConstraint(item: labelTwo, attribute: .top, relatedBy: .equal, toItem: labelOne, attribute: .bottom, multiplier: 1, constant: screenHeight + 200))
    view.addConstraint(NSLayoutConstraint(item: labelTwo, attribute: .right, relatedBy: .equal, toItem: labelOne, attribute: .right, multiplier: 1, constant: 0))
    view.addConstraint(NSLayoutConstraint(item: labelTwo, attribute: .left, relatedBy: .equal, toItem: labelOne, attribute: .left, multiplier: 1, constant: 0)     

    }

}

Solution 1

It is easy to use constraints to define the scroll content size - so you don't have to do any manual calculations.

Just remember:

1. The content elements of your scroll view must have left / top / width / height values. In the case of objects such as labels, they have intrinsic sizes, so you only have to define the left & top.
2. The content elements of your scroll view also define the bounds of the scrollable area - the contentSize - but they do so with the bottom & right constraints.
3. Combining those two concepts, you see that you need a "continuous chain" with at least one element defining the top / left / bottom / right extents.

Here is a simple example, that will run directly in a Playground page:

import UIKit
import PlaygroundSupport

class TestViewController : UIViewController {

    let labelOne: UILabel = {
        let label = UILabel()
        label.text = "Scroll Top"
        label.backgroundColor = .red
        label.translatesAutoresizingMaskIntoConstraints = false
        return label
    }()

    let labelTwo: UILabel = {
        let label = UILabel()
        label.text = "Scroll Bottom"
        label.backgroundColor = .green
        label.translatesAutoresizingMaskIntoConstraints = false
        return label
    }()

    let scrollView: UIScrollView = {
        let v = UIScrollView()
        v.translatesAutoresizingMaskIntoConstraints = false
        v.backgroundColor = .cyan
        return v
    }()


    override func viewDidLoad() {
        super.viewDidLoad()

        // add the scroll view to self.view
        self.view.addSubview(scrollView)

        // constrain the scroll view to 8-pts on each side
        scrollView.leftAnchor.constraint(equalTo: view.leftAnchor, constant: 8.0).isActive = true
        scrollView.topAnchor.constraint(equalTo: view.topAnchor, constant: 8.0).isActive = true
        scrollView.rightAnchor.constraint(equalTo: view.rightAnchor, constant: -8.0).isActive = true
        scrollView.bottomAnchor.constraint(equalTo: view.bottomAnchor, constant: -8.0).isActive = true

        // add labelOne to the scroll view
        scrollView.addSubview(labelOne)

        // constrain labelOne to left & top with 16-pts padding
        // this also defines the left & top of the scroll content
        labelOne.leadingAnchor.constraint(equalTo: scrollView.leadingAnchor, constant: 16.0).isActive = true
        labelOne.topAnchor.constraint(equalTo: scrollView.topAnchor, constant: 16.0).isActive = true

        // add labelTwo to the scroll view
        scrollView.addSubview(labelTwo)

        // constrain labelTwo at 400-pts from the left
        labelTwo.leadingAnchor.constraint(equalTo: scrollView.leadingAnchor, constant: 400.0).isActive = true

        // constrain labelTwo at 1000-pts from the top
        labelTwo.topAnchor.constraint(equalTo: scrollView.topAnchor, constant: 1000).isActive = true

        // constrain labelTwo to right & bottom with 16-pts padding
        labelTwo.rightAnchor.constraint(equalTo: scrollView.rightAnchor, constant: -16.0).isActive = true
        labelTwo.bottomAnchor.constraint(equalTo: scrollView.bottomAnchor, constant: -16.0).isActive = true

    }

}


let vc = TestViewController()
vc.view.backgroundColor = .yellow
PlaygroundPage.current.liveView = vc

Solution 2

Two things.

1. Add the labels to scroll view, not your view

You want your label to scroll with scroll view, then you should not add it on your view. When running your code, you can scroll but the fixed label there is pinned to your view, not on your scroll view

2. Make sure you added your constraints correctly

Try it on your storyboard about what combination of constraint is enough for a view. At least 4 constraints are needed for a label.

Bottom line

Here is a modified version of your code. For constraint I added padding left, padding top, width and height and it works. My code is

let labelOne: UILabel = {
    let label = UILabel()
    label.text = "Scroll Top"
    label.backgroundColor = .red
    label.translatesAutoresizingMaskIntoConstraints = false
    return label
}()

let labelTwo: UILabel = {
    let label = UILabel()
    label.text = "Scroll Bottom"
    label.backgroundColor = .green
    label.translatesAutoresizingMaskIntoConstraints = false
    return label
}()


override func viewDidLoad() {
    super.viewDidLoad()

    let screensize: CGRect = UIScreen.main.bounds
    let screenWidth = screensize.width
    let screenHeight = screensize.height
    var scrollView: UIScrollView!
    scrollView = UIScrollView(frame: CGRect(x: 0, y: 120, width: screenWidth, height: screenHeight))

    scrollView.addSubview(labelTwo)

    NSLayoutConstraint(item: labelTwo, attribute: .leading, relatedBy: .equal, toItem: scrollView, attribute: .leadingMargin, multiplier: 1, constant: 10).isActive = true
    NSLayoutConstraint(item: labelTwo, attribute: .width, relatedBy: .equal, toItem: nil, attribute: .notAnAttribute, multiplier: 1, constant: 200).isActive = true
    NSLayoutConstraint(item: labelTwo, attribute: .top, relatedBy: .equal, toItem: scrollView, attribute: .topMargin, multiplier: 1, constant: 10).isActive = true
    NSLayoutConstraint(item: labelTwo, attribute: .height, relatedBy: .equal, toItem: nil, attribute: .notAnAttribute, multiplier: 1, constant: 30).isActive = true

    scrollView.contentSize = CGSize(width: screenWidth, height: 2000)
    view.addSubview(scrollView)

}

And the scroll view looks like this

Solution 3

For me this work like charm

class WithDrawConfirmationViewController: UIViewController, WithDrawConfirmationViewProtocol {

    var presenter: WithDrawConfirmationPresenterProtocol?
    private let viewbackgroundColor = UIColor(hexString: "#F5F5F8")
    // MARK:- View properties
    lazy var scrollView: UIScrollView = {
        let scrollView = UIScrollView()
        //view.backgroundColor = .red
        scrollView.translatesAutoresizingMaskIntoConstraints = false
        return scrollView
    }()
    
    lazy var contentView: UIView = {
        let view = UIView()
        //view.backgroundColor = .green
        view.translatesAutoresizingMaskIntoConstraints = false
        return view
    }()
    
    lazy var headerView: UIView = {
        let view = UIView()
        view.translatesAutoresizingMaskIntoConstraints = false
        return view
    }()
    
    private lazy var titleLabel:UILabel = {
        let label = UILabel()
        label.translatesAutoresizingMaskIntoConstraints = false
        label.textColor = UIColor.themeBlack
        label.text = "Withdraw Confirmation"//"Loading.."
        label.textAlignment = .center
        label.font = UIFont(name: "AvenirNext-DemiBold", size: 20)
        label.numberOfLines = 0
        label.lineBreakMode = .byWordWrapping
        return label
    }()
    
    
    private lazy var descriptionLabel:UILabel = {
        let label = UILabel()
        label.translatesAutoresizingMaskIntoConstraints = false
        label.textColor = UIColor.themeGray
        label.text = "Please confirm your fixed deposit details before withdrawing your deposit"// "Loading.."
        label.textAlignment = .center
        label.font = UIFont(name: "AvenirNext-Medium", size: 14)
        label.numberOfLines = 0
        label.lineBreakMode = .byWordWrapping
        label.setContentHuggingPriority(1000, for: .vertical)
        return label
    }()
    
    private lazy var instructionLabel: UILabel = {
        let label = UILabel()
        label.translatesAutoresizingMaskIntoConstraints = false
        label.textColor = UIColor.themeGray
        label.text = "Complete fixed deposit will be withdrawn and the money will be debited to your account within 1-2 working days."//"Loading.."
        label.textAlignment = .left
        label.font = UIFont(name: "AvenirNext-Medium", size: 14)
        label.numberOfLines = 0
        label.lineBreakMode = .byWordWrapping
        return label
    }()
    
    private lazy var warningLabel: UILabel = {
        let label = UILabel()
        label.translatesAutoresizingMaskIntoConstraints = false
        label.textColor = UIColor.themeBlue
        label.text = "Axis bank will levy a penalty of 1% - 2% for premature withdrawal"//"Loading.."
        label.textAlignment = .left
        label.font = UIFont(name: "AvenirNext-DemiBold", size: 13)
        label.numberOfLines = 0
        label.lineBreakMode = .byWordWrapping
        return label
    }()
    
    private lazy var warningView: UIView = {
        let view = UIView()
        view.cornerradius = 5
        view.backgroundColor = UIColor(hexFromString: "#E8F4FD")
        view.translatesAutoresizingMaskIntoConstraints = false
        return view
    }()
    private lazy var fdInformationDetailView: FDPurchaseDetailView = {
        let view = FDPurchaseDetailView(isPoweredByViewVisible: false)
        //view.backgroundColor = .red
        view.translatesAutoresizingMaskIntoConstraints = false
        return view
    }()
    
    private lazy var footerCTAView: FooterButtonViewView = {
        let view = FooterButtonViewView()
        view.translatesAutoresizingMaskIntoConstraints = false
        return view
    }()
    
    // MARK:- Life cycle
    override func viewDidLoad() {
        super.viewDidLoad()
        contentView.backgroundColor = viewbackgroundColor
        scrollView.backgroundColor = viewbackgroundColor
        setUpUI()
        presenter?.viewDidLoadTriggered()
    }

    override func viewDidLayoutSubviews() {
        super.viewDidLayoutSubviews()
    }
    
    private func setUpUI() {
        view.addSubview(scrollView)
        scrollView.addSubview(contentView)
        view.backgroundColor = viewbackgroundColor
        addFooter()
        setUpHeaderView()
        setUpFDDetailView()
        setUpInformationAndWarningView()
        //scrollView.backgroundColor = .lightGray
        scrollView.leadingAnchor.constraint(equalTo: view.leadingAnchor).isActive = true
        scrollView.trailingAnchor.constraint(equalTo: view.trailingAnchor).isActive = true
        scrollView.topAnchor.constraint(equalTo: view.safeAreaLayoutGuide.topAnchor).isActive = true
        scrollView.bottomAnchor.constraint(equalTo: footerCTAView.topAnchor).isActive = true
        scrollView.contentInset = UIEdgeInsets(top: 0, left: 0, bottom: 100, right: 0)
        
        contentView.leadingAnchor.constraint(equalTo: scrollView.leadingAnchor).isActive = true
        contentView.trailingAnchor.constraint(equalTo: scrollView.trailingAnchor).isActive = true
        contentView.topAnchor.constraint(equalTo: scrollView.topAnchor).isActive = true
        contentView.bottomAnchor.constraint(equalTo: scrollView.bottomAnchor).isActive = true
        contentView.widthAnchor.constraint(equalTo: view.widthAnchor).isActive = true
        //contentView.bottomAnchor.constraint(equalTo: footerCTAView.topAnchor).isActive = true
    }
    
    private func setUpHeaderView() {
        contentView.addSubview(headerView)
        headerView.addSubviews([titleLabel, descriptionLabel])
        
        headerView.leadingAnchor.constraint(equalTo: contentView.leadingAnchor, constant: 20).isActive = true
        headerView.trailingAnchor.constraint(equalTo: contentView.trailingAnchor, constant: -20).isActive = true
        headerView.topAnchor.constraint(equalTo: contentView.topAnchor, constant: 4).isActive = true
       
        titleLabel.leadingAnchor.constraint(equalTo: headerView.leadingAnchor, constant: 8).isActive = true
        titleLabel.trailingAnchor.constraint(equalTo: headerView.trailingAnchor).isActive = true
        titleLabel.topAnchor.constraint(equalTo: headerView.topAnchor, constant: 8).isActive = true
        
        descriptionLabel.topAnchor.constraint(equalTo: titleLabel.bottomAnchor, constant:  20).isActive = true
        descriptionLabel.leadingAnchor.constraint(equalTo: headerView.leadingAnchor, constant: 8).isActive = true
        descriptionLabel.trailingAnchor.constraint(equalTo: headerView.trailingAnchor).isActive = true
        descriptionLabel.bottomAnchor.constraint(equalTo: headerView.bottomAnchor, constant: -20).isActive = true
    }
    
    
    private func setUpFDDetailView() {
        contentView.addSubview(fdInformationDetailView)
        fdInformationDetailView.topAnchor.constraint(equalTo: headerView.bottomAnchor).isActive = true
        fdInformationDetailView.leadingAnchor.constraint(equalTo: contentView.leadingAnchor, constant: 20).isActive = true
        fdInformationDetailView.trailingAnchor.constraint(equalTo: contentView.trailingAnchor, constant: -20).isActive = true
       
    }
    
    private func setUpInformationAndWarningView() {
        contentView.addSubview(instructionLabel)
        
        instructionLabel.topAnchor.constraint(equalTo: fdInformationDetailView.bottomAnchor, constant: 20).isActive = true
        instructionLabel.leadingAnchor.constraint(equalTo: contentView.leadingAnchor, constant: 20).isActive = true
        instructionLabel.trailingAnchor.constraint(equalTo: contentView.trailingAnchor, constant: -20).isActive = true
        
        warningView.addSubview(warningLabel)
        warningLabel.topAnchor.constraint(equalTo: warningView.topAnchor, constant: 8).isActive = true
        warningLabel.leadingAnchor.constraint(equalTo: warningView.leadingAnchor, constant: 20).isActive = true
        warningLabel.trailingAnchor.constraint(equalTo: warningView.trailingAnchor, constant: -20).isActive = true
        warningLabel.bottomAnchor.constraint(equalTo: warningView.bottomAnchor, constant: -8).isActive = true
        
        contentView.addSubview(warningView)
        
        warningView.topAnchor.constraint(equalTo: instructionLabel.bottomAnchor, constant: 8).isActive = true
        warningView.leadingAnchor.constraint(equalTo: contentView.leadingAnchor, constant: 20).isActive = true
        warningView.trailingAnchor.constraint(equalTo: contentView.trailingAnchor, constant: -20).isActive = true
       //warningView.centerXAnchor.constraint(equalTo: contentView.centerXAnchor).isActive = true
        warningView.bottomAnchor.constraint(greaterThanOrEqualTo: contentView.bottomAnchor, constant: -20).isActive = true
        
    }
    
    private func addFooter() {
        view.addSubview(footerCTAView)
        footerCTAView.delegate = self
        footerCTAView.leadingAnchor.constraint(equalTo: view.leadingAnchor).isActive = true
        footerCTAView.trailingAnchor.constraint(equalTo: view.trailingAnchor).isActive = true
        footerCTAView.bottomAnchor.constraint(equalTo: view.safeAreaLayoutGuide.bottomAnchor).isActive = true
    }
}