How to scroll a list horizontally in SwiftUI?

Question

In iOS 14 you can use ScrollViewReader to automatically scroll your view up or down as the content in the scrollview changes.

I'm in a situation where I have to support iOS 13. Is there a way, even a hacky way, to programmatically scroll the scrollview in iOS 13?

For that, I write the following code it works with vertical scrolling but I need horizontal scroll and it needs to move the selected Index.

    struct ListScrollingHelper: UIViewRepresentable {
        let proxy: ListScrollingProxy // reference type
    
        func makeUIView(context: Context) -> UIView {
            return UIView() // managed by SwiftUI, no overloads
        }
    
        func updateUIView(_ uiView: UIView, context: Context) {
            proxy.catchScrollView(for: uiView) // here UIView is in view hierarchy
        }
    }

class ListScrollingProxy {
    enum Action {
        case end
        case top
        case point(point: CGPoint)     // << bonus !!
    }

    private var scrollView: UIScrollView?

    func catchScrollView(for view: UIView) {
        if nil == scrollView {
            scrollView = view.enclosingScrollView()
        }
    }

    func scrollTo(_ action: Action) {
        if let scroller = scrollView {
            var rect = CGRect(origin: .zero, size: CGSize(width: 1, height: 1))
            switch action {
                case .end:
                    rect.origin.y = scroller.contentSize.height +
                        scroller.contentInset.bottom + scroller.contentInset.top - 1
                case .point(let point):
                    rect.origin.y = point.y
                default: {
                    // default goes to top
                }()
            }
            scroller.scrollRectToVisible(rect, animated: true)
        }
    }
}

extension UIView {
    func enclosingScrollView() -> UIScrollView? {
        var next: UIView? = self
        repeat {
            next = next?.superview
            if let scrollview = next as? UIScrollView {
                return scrollview
            }
        } while next != nil
        return nil
    }
}

i use my code as follows:

struct ContentView: View {
    private let scrollingProxy = ListScrollingProxy() // proxy helper

    var body: some View {
        VStack {
            HStack {
                Button(action: { self.scrollingProxy.scrollTo(.top) }) { // < here
                    Image(systemName: "arrow.up.to.line")
                      .padding(.horizontal)
                }
                Button(action: { self.scrollingProxy.scrollTo(.end) }) { // << here
                    Image(systemName: "arrow.down.to.line")
                      .padding(.horizontal)
                }
            }
            Divider()
            List {
                ForEach(0 ..< 200) { i in
                    Text("Item \(i)")
                        .background(
                           ListScrollingHelper(proxy: self.scrollingProxy) // injection
                        )
                }
            }
        }
    }
}

Andy Jazz · Accepted Answer · 2021-07-06 10:57:45Z

1

Use the following approach:

import SwiftUI

struct ContentView: View {    
    
    var body: some View {            
        ScrollView(.horizontal, showsIndicators: false) {
            HStack(spacing: 10) {
                ForEach(1..<11) {
                    Text("ITEM \($0)")
                        .frame(width: 70, height: 70)
                }
            }
        }
    }
}

Scrolling a whole table looks like this:

struct ContentView: View {
        
    var body: some View {
        List {
            ScrollView(.horizontal, showsIndicators: false) {       
                Text("First List Item in a first cell")
                Text("Second List Item in a second cell")
                Text("Third List Item in a third cell")
            }
        }
    }
}

You can combine both methodologies.

edited Jul 6, 2021 at 10:57

answered Jul 6, 2021 at 10:17

Andy Jazz

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1 Comment

Anisetty Mounika Over a year ago

Here where we can use the scroll view scroll property

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