下拉关闭 + velocity 接力

拖卡片下滑——松手时根据 translation 与 velocity 决定回弹还是关闭。velocity 直接喂给 spring 让动画'接住'手势。

ch. 4

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调参

distance150ptvelocity800pt/s

drag down ↓

对照 SwiftUI

// SwiftUI 17+ — DragGesture.velocity 接力 spring
.gesture(
    DragGesture(minimumDistance: 8)
        .onChanged { dragY = $0.translation.height }
        .onEnded { v in
            let dy = v.translation.height
            let vy = v.velocity.height                  // iOS 17+ pt/s
            let dismiss = dy > 150 || vy > 800
            withAnimation(.interactiveSpring(
                response: 0.42,
                dampingFraction: 0.86)) {
                dragY = dismiss ? 900 : 0
            }
        }
)

左侧是 Web 复刻（Motion / React），右侧是等价的 SwiftUI 写法。两边 spring 数学一致。