A SwiftUI & Combine powered scroll-offset sampling component that lets you monitor ScrollView offsets smoothly and efficiently by sampling at intervals and filtering out insignificant changes.

• Timed Sampling Sample the latest offset at regular intervals (default 0.25s), avoiding excessive updates every frame.
• Minimum-Difference Filtering Only trigger updates when offset changes exceed a threshold (default 2.0pt), cutting down jitter noise.
• Background ↔ Main Dispatch Perform sampling on a background queue and publish on the main thread for safe, smooth UI updates.
• Configurable Customize sampling interval (sampleInterval) and minimum-difference threshold (minDifference).
• Axes & Indicators Monitor horizontal, vertical, or both axes, and choose whether to show scroll indicators.

1. In Xcode, select File → Swift Packages → Add Package Dependency...

2. Enter the repository URL, for example:

   https://github.com/asyncawaited/ScrollOffsetReader.git
   

3. Specify a version range (e.g. from: "1.0.0").

import SwiftUI
import ScrollOffsetReader

struct ContentView: View {
    @State private var offset: CGSize = .zero

    var body: some View {
        VStack {
            Text("Offset: x=\(offset.width, specifier: "%.1f"), y=\(offset.height, specifier: "%.1f")")
                .padding()

            ScrollOffsetReader(
                scrollOffset: $offset,
                axes: .vertical,
                showsIndicators: false,
                sampleInterval: 0.2,   // Default 0.25
                minDifference: 1.0     // Default 2.0
            ) {
                LazyVStack {
                    ForEach(0..<100) { i in
                        Text("Item \(i)")
                            .frame(height: 50)
                    }
                }
            }
        }
    }
}

1. OffsetSampler

   • Uses a CurrentValueSubject<CGSize, Never> to accept raw offsets.
   • Applies a custom sample(with:) extension to combine offsets with a timer, taking only the latest value when the timer fires.
   • Removes duplicate values and publishes on the main thread via @Published var sampledOffset.

2. ScrollOffsetModifier

   • Holds OffsetSampler as a @StateObject.
   • Captures per-frame offsets via a PreferenceKey and forwards them to sampler.update(offset:).
   • Listens to sampler.$sampledOffset and writes sampled values back to the bound scrollOffset.

3. ScrollOffsetReader

   • Wraps a ScrollView, ZStack, ScrollOffsetProxy, and ScrollOffsetModifier into one reusable component for one-line integration.

• Swift: 5.9+
• iOS: 13.0+
• macOS: 11.0+
• Xcode: 15.0+

MIT © Royal

基于 SwiftUI & Combine 的滚动偏移采样组件，帮助你在 ScrollView 中高效、平滑地监听滚动位置，并自动过滤无意义的小幅度抖动。

• 定时采样 每隔指定时间间隔（默认 0.25s）采样最新偏移，避免在每帧都更新导致的性能问题。
• 最小差值过滤 仅当偏移变化超过阈值（默认 2.0pt）时才触发，减少抖动噪声。
• 后台 ↔ 主线程调度 在后台队列中采样，主线程上发布，确保 UI 更新安全且不卡顿。
• 可定制 自定义采样间隔（sampleInterval）和最小差值阈值（minDifference）。
• 多轴 & 滚动条 支持监测水平、垂直或双轴滚动，并可选择性显示或隐藏滚动条。

1. 在 Xcode 中选择 File → Swift Packages → Add Package Dependency...

2. 输入仓库地址，例如：

   https://github.com/asyncawaited/ScrollOffsetReader.git
   

3. 指定版本区间（例如 from: "1.0.0"）。

import SwiftUI
import ScrollOffsetReader

struct ContentView: View {
    @State private var offset: CGSize = .zero

    var body: some View {
        VStack {
            Text("偏移: x=\(offset.width, specifier: "%.1f"), y=\(offset.height, specifier: "%.1f")")
                .padding()

            ScrollOffsetReader(
                scrollOffset: $offset,
                axes: .vertical,
                showsIndicators: false,
                sampleInterval: 0.2,   // 默认 0.25
                minDifference: 1.0     // 默认 2.0
            ) {
                LazyVStack {
                    ForEach(0..<100) { i in
                        Text("Item \(i)")
                            .frame(height: 50)
                    }
                }
            }
        }
    }
}

1. OffsetSampler

   • 使用 CurrentValueSubject<CGSize, Never> 接收原始偏移；
   • 自定义 sample(with:) 将偏移与定时器结合，仅在定时器触发时取最新值；
   • 去重并在主线程通过 @Published var sampledOffset 发布。

2. ScrollOffsetModifier

   • 将 OffsetSampler 以 @StateObject 持有；
   • 通过 PreferenceKey 捕获每帧偏移并调用 update(offset:)；
   • 监听 sampler.$sampledOffset，将采样结果写回绑定的 scrollOffset。

3. ScrollOffsetReader

   • 封装 ScrollView + ZStack + ScrollOffsetProxy + ScrollOffsetModifier，一行代码即可使用。

• Swift: 5.9+
• iOS: 13.0+
• macOS: 11.0+
• Xcode: 15.0+

MIT © Royal