SwiftUI ScrollView Прокрутка до относительной позиции

Question

У меня большой горизонтальный вид, который не помещается на экране, поэтому я помещаю его в горизонтальный ScrollView. Если 0 будет представлять полностью прокрученный влево, а 1 - полностью вправо - как я могу, например, прокрутить до относительной позиции 0,8?

Поскольку я не могу прикрепить идентификатор к дочернему элементу ScrollViewReader не работает.

      struct ContentView: View {

    var body: some View {
        ScrollView(.horizontal) {
            Text("Example for a long view without individual elements that you could use id on. Example for a long view without individual elements that you could use id on. Example for a long view without individual elements that you could use id on. Example for a long view without individual elements that you could use id on. Example for a long view without individual elements that you could use id on. Example for a long view without individual elements that you could use id on. Example for a long view without individual elements that you could use id on. Example for a long view without individual elements that you could use id on. Example for a long view without individual elements that you could use id on. Example for a long view without individual elements that you could use id on.")
        }
    }
}

Answer 1

Вы можете решить эту проблему в чистом SwiftUI, используя ZStack с невидимым фоном:

      struct ContentView: View {
    
    var body: some View {
        ScrollViewReader { reader in
            ScrollView(.horizontal) {
                ZStack {
                    HStack {
                        ForEach(0..<100) { i in
                            Spacer().id(i)
                        }
                    }
                    Text("Example for a long view without individual elements that you could use id on. Example for a long view without individual elements that you could use id on. Example for a long view without individual elements that you could use id on. Example for a long view without individual elements that you could use id on. Example for a long view without individual elements that you could use id on. Example for a long view without individual elements that you could use id on. Example for a long view without individual elements that you could use id on. Example for a long view without individual elements that you could use id on. Example for a long view without individual elements that you could use id on. Example for a long view without individual elements that you could use id on.")
                }
            }
            Button("Go to 0.8") {
                withAnimation {
                    reader.scrollTo(80)
                }
            }
        }
    }
}

Answer 2

С SwiftUI-Introspect, используемым для «изучения основных компонентов UIKit из SwiftUI», мы можем добиться этого.

Вот как это делается, в комплекте с Slider чтобы продемонстрировать его работу:

      struct ContentView: View {
    @State private var relativePosition: CGFloat = 0.5
    
    var body: some View {
        VStack {
            ScrollView(.horizontal) {
                Text("Example for a long view without individual elements that you could use id on. Example for a long view without individual elements that you could use id on. Example for a long view without individual elements that you could use id on. Example for a long view without individual elements that you could use id on. Example for a long view without individual elements that you could use id on. Example for a long view without individual elements that you could use id on. Example for a long view without individual elements that you could use id on. Example for a long view without individual elements that you could use id on. Example for a long view without individual elements that you could use id on. Example for a long view without individual elements that you could use id on.")
            }
            .introspectScrollView { scrollView in
                let width = scrollView.contentSize.width - scrollView.frame.width
                scrollView.contentOffset.x = relativePosition * width
            }
            
            let _ = relativePosition  // Needed to update view
            
            Slider(value: $relativePosition, in: 0 ... 1)
        }
    }
}