Ios 有没有办法观察滚动的SwiftUI图表的内容偏移量

按照你的方法， 我增加了一些改进，我增加了左边距和右边距，允许在滚动时进行适当的 Select ，还定义了一个ScrollPosition，它是Int来跟踪您的数据所选的索引.

如果要更改顶部显示的值，只需根据需要将selectionText函数修改为返回.value

希望这就是你想要的.

import SwiftUI
import Charts

struct SampleModel: Identifiable {
    var id = UUID()
    var date: String
    var value: Double
    var animate: Bool = false
}

struct ContentView: View {
    @State private var data = [
        SampleModel(date: "26\nFr", value: 9.2),
        SampleModel(date: "27\nSa", value: 12.5),
        SampleModel(date: "28\nSu", value: 15.0),
        SampleModel(date: "29\nMo", value: 20.0),
        SampleModel(date: "30\nTu", value: 5.0),
        SampleModel(date: "31\nWe", value: 7.0),
        SampleModel(date: "01\nTh", value: 3.0),
        SampleModel(date: "02\nFr", value: 20.0),
        SampleModel(date: "03\nSa", value: 5.0),
        SampleModel(date: "04\nSu", value: 7.0),
        SampleModel(date: "05\nMo", value: 3.0),
        SampleModel(date: "06\nTu", value: 10.0),
        SampleModel(date: "07\nWe", value: 21.0),
        SampleModel(date: "08\nTh", value: 14.0),
        SampleModel(date: "09\nFr", value: 10.0),
        SampleModel(date: "10\nSt", value: 7.0),
        SampleModel(date: "11\nSu", value: 15.0),
        SampleModel(date: "12\nMo", value: 17.0),
        SampleModel(date: "13\nTu", value: 29.0)
    ]
    @State private var scrollPosition: Int = 0
    @State var priceText: String? = nil
    @State var selectedIndex: Int = 0

    var body: some View {
        GeometryReader { geometry in
            VStack {
                if let price = priceText {
                    Text(price)
                        .padding()
                }

                    Text(selectionText())
                        .padding()

                Chart(Array(zip(data.indices, data)), id: \.0) { index, flight in
                    BarMark(x: .value("Index", index),
                            y: .value("Price", flight.value), width: .fixed(10))
                    .foregroundStyle(
                        Gradient(
                            colors: [
                                .blue,
                                .green
                            ]
                        )
                    )
                    .clipShape(RoundedRectangle(cornerRadius: 16))
                }
                .frame(height: 180)
                .background(content: {
                    VStack {
                        Color.gray.frame(width: 1)
                        Color.clear.frame(height: 40)
                    }
                })
                .chartXAxis(content: {
                    AxisMarks(preset: .aligned, position: .bottom, values: .stride(by: 1)) { value in
                        let label = data[value.index].date
                        AxisValueLabel(label)
                            .foregroundStyle(.gray)
                    }
                })
                .chartXVisibleDomain(length: 10)
                .chartYAxis(.hidden)
                .chartScrollTargetBehavior(
                    .valueAligned(unit: 1)
                )
                .chartScrollableAxes(.horizontal)
                .chartScrollPosition(x: $scrollPosition)
                .contentMargins(Edge.Set(arrayLiteral: [.leading, .trailing]), geometry.size.width/2)
            }
        }
    }

    private func selectionText() -> String {
        guard scrollPosition >= .zero else {
            return data[.zero].date
        }

        guard scrollPosition < data.count else {
            return data[data.count - 1].date
        }

        return data[scrollPosition].date
    }
}