SwiftUI_Horizontal_Infinity_ScrollView

gistfile1.txt

import SwiftUI

struct ContentView: View {
    
    @State private var text = ""

    @State  private var evnent = HorizontalEvent(forEachCount: 1)
    var body: some View {
        ZStack {
            HorizontalScrollView(event: self.evnent, action: { tex in
                self.evnent.forEachCount += Int(tex) ?? 0
                self.text = self.evnent.forEachCount.description
            })
            Text(self.text)
        }
    }
}

class HorizontalEvent: ObservableObject {

    var forEachCount: Int

    init(forEachCount: Int) {
        self.forEachCount = forEachCount
    }
}


struct HorizontalScrollView: View {

    var rect = CGRect()
    var evnents: HorizontalEvent
    let action: (_ tex: String) -> Void

    private var scText = "無限スクロール"
    @State private var index: Int = 0
    @State private var offset: CGFloat = 0

    init(event :HorizontalEvent, action: @escaping (String) -> Void) {
        rect = UIScreen.main.bounds
        self.evnents = event
        self.action = action
    }

    var body: some View {
        ScrollView(.horizontal,showsIndicators: false) {
            HStack {
                ForEach(0..<self.evnents.forEachCount, id: \.self) { i in
                        Text("\(self.scText)").offset(y: -20)
                        .frame(minWidth: 0, maxWidth: .infinity,  minHeight: 0, maxHeight: .infinity)
                }
            }
        }
        .content.offset(x: self.offset/2)
        .frame(width: rect.width * CGFloat(self.evnents.forEachCount), alignment: .center)
        .gesture(DragGesture()
        .onChanged({ value in
            self.offset = value.translation.width - self.rect.width * CGFloat(self.index)
        })
            .onEnded({ value in
                let scrollThreshold = self.rect.width / 2
                if value.predictedEndTranslation.width < -scrollThreshold {
                    self.index = min(self.index+1, self.evnents.forEachCount)
                    self.action("\(1)")
                } else if value.predictedEndTranslation.width > scrollThreshold {
                    self.index = max(self.index-1, -self.evnents.forEachCount)
                }

                withAnimation {
                    self.offset = -self.rect.width * CGFloat(self.index)
                }
            })
        )
    }
}

struct ContentView_Previews: PreviewProvider {
    static var previews: some View {
        ContentView()
    }
}