SwiftUI - ScrollViewReader's scrollTo does not scroll

Question

Created Nov ’20

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I have a simple SwiftUI list that I want to scroll to a row when a user click on a button. This is my code that it suppose to work, but it does not do.

Code Block struct ContentView: View {
		var body: some View {
				ScrollViewReader { proxy in
						VStack {
								Button("Jump to #50") {
										proxy.scrollTo(5, anchor: .top)
								}
								List(0..<100) { i in
										Text("Example \(i)")
										.id(i)
								}
						}
				}
		}
}
struct ContentView_Previews: PreviewProvider {
		static var previews: some View {
				ContentView()
		}
}

I tested it on iOS 14.2 both on simulator and a physical device.

I read srollTo's documentation) but there is not much info.

So how to scroll to a row, for example, row 50?

Answered by OOPer in 648994022

Seems your link to the document is sort of broken (not your fault, the markdown-like processor of this site is broken),
but it is true the documentation of scrollTo(_:anchor:) is quite unkind.

As far as I tried, ScrollViewReader works only with:

Explicit use of ScrollView
List of identifiable collection

And it does not work with List of Range<Int>.

Please try this:

Code Block struct ContentView: View {
    var body: some View {
        ScrollViewReader { proxy in
            VStack {
                Button("Jump to #50") {
                    proxy.scrollTo(50, anchor: .top)
                }
                List(0..<100, id: \.self) { i in //<-
                    Text("Example \(i)")
                        .id(i)
                }
            }
        }
    }
}

(Please do not forget id: \.self on line 8, which makes List treat 0..<100 as an identifiable collection.)

I have found almost the same code on the web, so it may have once worked in a certain version of SwiftUI.

Boost

Answer 1

OOPer OP

Nov ’20

Accepted Answer

Seems your link to the document is sort of broken (not your fault, the markdown-like processor of this site is broken),
but it is true the documentation of scrollTo(_:anchor:) is quite unkind.

As far as I tried, ScrollViewReader works only with:

Explicit use of ScrollView
List of identifiable collection

And it does not work with List of Range<Int>.

Please try this:

Code Block struct ContentView: View {
    var body: some View {
        ScrollViewReader { proxy in
            VStack {
                Button("Jump to #50") {
                    proxy.scrollTo(50, anchor: .top)
                }
                List(0..<100, id: \.self) { i in //<-
                    Text("Example \(i)")
                        .id(i)
                }
            }
        }
    }
}

(Please do not forget id: \.self on line 8, which makes List treat 0..<100 as an identifiable collection.)

I have found almost the same code on the web, so it may have once worked in a certain version of SwiftUI.

2

Answer 2

mahan.no OP

Nov ’20

Thanks. It works after I added id: \.self

That is a bug in Apple's Editor. Link is broken If it ends with )

0