How to use Swift UIScrollView

Implement UIScrollView in code

I'm self-taught to make an app, but by the way, I thought I had never used scrollView, so I studied! First, I tried using scrollView without looking at it at all. Here is the code

class ViewController: UIViewController {
    
    private let label = UILabel()
    
    override func viewDidLoad() {
        super.viewDidLoad()
        
        let scrollView = UIScrollView()
        
        scrollView.frame = .init(x: 0, y: 0, 
            width: view.frame.size.width, height: view.frame.size.height)
        
        view.addSubview(scrollView)
        scrollView.addSubview(label)
        
        label.text = "hello world"
        label.frame = .init(x: 0, y: 0, width: 100, height: 50)
        label.center = scrollView.center
    }
    
}

The result could not be scrolled. label is added to make sure that scrollView is displayed properly.

why! ?? It seems that you have to specify something called contentSize. contentSize seems to determine the scroll area. Here is the corrected one

class ViewController: UIViewController {
    
    private let label = UILabel()
    
    override func viewDidLoad() {
        super.viewDidLoad()
        
        let scrollView = UIScrollView()
        
        //Set the size of scrollView.
        scrollView.frame = .init(x: 0, y: 0, 
            width: view.frame.size.width * 2, height: view.frame.size.height * 2)
        
        //Scroll area settings
        scrollView.contentSize = CGSize(width:view.frame.size.width * 2, height:view.frame.size.height * 2)
        
        //Add scrollView as SubView of view
        view.addSubview(scrollView)
        scrollView.addSubview(label)
        
        label.text = "hello world"
        label.frame = .init(x: 0, y: 0, width: 100, height: 50)
        label.center = scrollView.center
    }
    
}

How about this! I built it, but I couldn't scroll.

Upon further investigation, it seems that frame must be smaller than contentSize.

class ViewController: UIViewController {
    
    private let label = UILabel()
    
    override func viewDidLoad() {
        super.viewDidLoad()
        
        let scrollView = UIScrollView()
        
        //Set the size of scrollView.
        scrollView.frame = .init(x: 0, y: 0, 
            width: view.frame.size.width, height: view.frame.size.height)
        
        //Scroll area settings
        scrollView.contentSize = CGSize(width:view.frame.size.width * 2, height:view.frame.size.height * 2)
        
        //Add scrollView as SubView of view
        view.addSubview(scrollView)
        scrollView.addSubview(label)
        
        label.text = "hello world"
        label.frame = .init(x: 0, y: 0, width: 100, height: 50)
        label.center = scrollView.center
    }
    
}

The result is ... I got it! !! !!

Summary

When using UIScrollView

contentSize must be specified contentSize must be larger than frame

Please note that and implement it!

Quote

[Swift4] How to use scroll view