为什么我的垂直编程滚动视图在 Swift 中不起作用

Question

I have created a test project to see if I can get a swift programmatic scroll view to work and I just cannot get the test data to scroll. Here is my test code.

import UIKit

class ViewController: UIViewController {

    private let viewLabel0: UILabel = {
        let label = UILabel()
        label.text = "Stephen 0"
        label.font = UIFont.systemFont(ofSize: 30)
        label.textColor = .white
        return label
    }()
    

    private let viewLabel1: UILabel = {
        let label = UILabel()
        label.text = "Stephen 1"
        label.font = UIFont.systemFont(ofSize: 30)
        label.textColor = .white
        return label
    }()

    private let viewLabel2: UILabel = {
        let label = UILabel()
        label.text = "Stephen 2"
        label.font = UIFont.systemFont(ofSize: 30)
        label.textColor = .white
        return label
    }()

    private let viewLabel3: UILabel = {
        let label = UILabel()
        label.text = "Stephen 3"
        label.font = UIFont.systemFont(ofSize: 30)
        label.textColor = .white
        return label
    }()

    private let viewLabel4: UILabel = {
        let label = UILabel()
        label.text = "Stephen 4"
        label.font = UIFont.systemFont(ofSize: 30)
        label.textColor = .white
        return label
    }()
    
    private let viewLabel5: UILabel = {
        let label = UILabel()
        label.text = "Stephen 5"
        label.font = UIFont.systemFont(ofSize: 30)
        label.textColor = .white
        return label
    }()

    private let viewLabel6: UILabel = {
        let label = UILabel()
        label.text = "Stephen 6"
        label.font = UIFont.systemFont(ofSize: 30)
        label.textColor = .white
        return label
    }()
    

    private let viewLabel7: UILabel = {
        let label = UILabel()
        label.text = "Stephen 7"
        label.font = UIFont.systemFont(ofSize: 30)
        label.textColor = .white
        return label
    }()

    private let viewLabel8: UILabel = {
        let label = UILabel()
        label.text = "Stephen 8"
        label.font = UIFont.systemFont(ofSize: 30)
        label.textColor = .white
        return label
    }()

    private let viewLabel9: UILabel = {
        let label = UILabel()
        label.text = "Stephen 9"
        label.font = UIFont.systemFont(ofSize: 30)
        label.textColor = .white
        return label
    }()

    private let viewLabel10: UILabel = {
        let label = UILabel()
        label.text = "Stephen 10"
        label.font = UIFont.systemFont(ofSize: 30)
        label.textColor = .white
        return label
    }()
    
    private let viewLabel11: UILabel = {
        let label = UILabel()
        label.text = "Stephen 11"
        label.font = UIFont.systemFont(ofSize: 30)
        label.textColor = .white
        return label
    }()

    private let viewLabel12: UILabel = {
        let label = UILabel()
        label.text = "Stephen 12"
        label.font = UIFont.systemFont(ofSize: 30)
        label.textColor = .white
        return label
    }()

    private let viewLabel13: UILabel = {
        let label = UILabel()
        label.text = "Stephen 13"
        label.font = UIFont.systemFont(ofSize: 30)
        label.textColor = .white
        return label
    }()
    
    private let viewLabel14: UILabel = {
        let label = UILabel()
        label.text = "Stephen 14"
        label.font = UIFont.systemFont(ofSize: 30)
        label.textColor = .white
        return label
    }()
    
    private lazy var scrollView: UIScrollView = {
        let sv = UIScrollView()
        sv.isScrollEnabled = true
        sv.contentSize = CGSize(width: self.view.frame.width, height: self.view.frame.height * 3.0)
        return sv
    }()
    
    private let contentView: UIView = {
        let cv = UIView()
        return cv
    }()
    
    override func viewDidLoad() {
        super.viewDidLoad()
        
        view.backgroundColor = UIColor.mainBackgroundColor
        
        view.addSubview(scrollView)
        scrollView.anchor(top: view.topAnchor,
                          left: view.leftAnchor,
                          bottom: view.bottomAnchor,
                          right: view.rightAnchor)
        
        scrollView.addSubview(contentView)
        contentView.anchor(top: scrollView.contentLayoutGuide.topAnchor,
                           left: scrollView.frameLayoutGuide.leftAnchor,
                           bottom: scrollView.contentLayoutGuide.bottomAnchor,
                           right: scrollView.frameLayoutGuide.rightAnchor,
                           paddingTop: 0,
                           paddingLeft: 0,
                           paddingBottom: 0,
                           paddingRight: 0)

        
        contentView.addSubview(viewLabel0)
        viewLabel0.anchor(top: view.safeAreaLayoutGuide.topAnchor, paddingTop: 40.0)
        viewLabel0.centerX(inView: contentView)

        contentView.addSubview(viewLabel1)
        viewLabel1.anchor(top: viewLabel0.bottomAnchor, paddingTop: 40.0)
        viewLabel1.centerX(inView: contentView)

        contentView.addSubview(viewLabel2)
        viewLabel2.anchor(top: viewLabel1.bottomAnchor, paddingTop: 40.0)
        viewLabel2.centerX(inView: contentView)

        contentView.addSubview(viewLabel3)
        viewLabel3.anchor(top: viewLabel2.bottomAnchor, paddingTop: 40.0)
        viewLabel3.centerX(inView: contentView)

        contentView.addSubview(viewLabel4)
        viewLabel4.anchor(top: viewLabel3.bottomAnchor, paddingTop: 40.0)
        viewLabel4.centerX(inView: contentView)

        contentView.addSubview(viewLabel5)
        viewLabel5.anchor(top: viewLabel4.bottomAnchor, paddingTop: 40.0)
        viewLabel5.centerX(inView: contentView)

        contentView.addSubview(viewLabel6)
        viewLabel6.anchor(top: viewLabel5.bottomAnchor, paddingTop: 40.0)
        viewLabel6.centerX(inView: contentView)

        contentView.addSubview(viewLabel7)
        viewLabel7.anchor(top: viewLabel6.bottomAnchor, paddingTop: 40.0)
        viewLabel7.centerX(inView: contentView)

        contentView.addSubview(viewLabel8)
        viewLabel8.anchor(top: viewLabel7.bottomAnchor, paddingTop: 40.0)
        viewLabel8.centerX(inView: contentView)

        contentView.addSubview(viewLabel9)
        viewLabel9.anchor(top: viewLabel8.bottomAnchor, paddingTop: 40.0)
        viewLabel9.centerX(inView: contentView)

        contentView.addSubview(viewLabel10)
        viewLabel10.anchor(top: viewLabel9.bottomAnchor, paddingTop: 40.0)
        viewLabel10.centerX(inView: contentView)

        contentView.addSubview(viewLabel11)
        viewLabel11.anchor(top: viewLabel10.bottomAnchor, paddingTop: 40.0)
        viewLabel11.centerX(inView: contentView)

        contentView.addSubview(viewLabel12)
        viewLabel12.anchor(top: viewLabel11.bottomAnchor, paddingTop: 40.0)
        viewLabel12.centerX(inView: contentView)

        contentView.addSubview(viewLabel13)
        viewLabel13.anchor(top: viewLabel12.bottomAnchor, paddingTop: 40.0)
        viewLabel13.centerX(inView: contentView)

        contentView.addSubview(viewLabel14)
        viewLabel14.anchor(top: viewLabel13.bottomAnchor, paddingTop: 40.0)
        viewLabel14.centerX(inView: contentView)

        
        
        
    }


}

I feel I have tried everything from looking in stack overflow to searching online but I simply cannot get it to scroll the list of labels I have created.

Answer 1

First of all you must not set your view properties in viewDidLoad, because in this method the view is loaded not appeared, try to put same code in viewDidAppear and also check content size property of you scroll view, it should match with your scroll content size and should be greater than you view size to scroll and also keep scrolling enable true for scroll view.

Second thing it would be better to take scroll from you storyboard.

Refer the link for implementation, I search on google you can also try other links.

https://medium.com/@pradeep_chauhan/how-to-configure-a-uiscrollview-with-auto-layout-in-interface-builder-218dcb4022d7

Answer 2

Needed the following code

       view.addSubview(scrollView)
        scrollView.anchor(top: self.view.topAnchor,
                          bottom: self.view.bottomAnchor,
                          paddingTop: 0,
                          paddingBottom: 0)
        scrollView.trail(left: self.view.leadingAnchor,
                         right: self.view.trailingAnchor,
                         leftT: 0,
                         rightT: 0)
        
        scrollView.addSubview(contentView)
        contentView.topAnchor.constraint(equalTo: scrollView.topAnchor).isActive = true;
        contentView.bottomAnchor.constraint(equalTo: scrollView.bottomAnchor).isActive = true;
        contentView.leadingAnchor.constraint(equalTo: scrollView.leadingAnchor).isActive = true;
        contentView.trailingAnchor.constraint(equalTo: scrollView.trailingAnchor).isActive = true;