Swiftui -计时器在一段时间内漂移

import SwiftUI

struct DriftingView: View {
    @State private var position: CGPoint = .zero
    @State private var timer: Timer?
    
    let driftDuration: TimeInterval = 5.0
    let driftSpeed: CGFloat = 100.0
    
    var body: some View {
        GeometryReader { geometry in
            Circle()
                .frame(width: 50, height: 50)
                .position(self.position)
                .onAppear {
                    self.startDrifting(in: geometry.size)
                }
        }
    }
    
    private func startDrifting(in size: CGSize) {
        self.timer = Timer.scheduledTimer(withTimeInterval: 0.1, repeats: true) { _ in
            let maxX = size.width - 25
            let maxY = size.height - 25
            
            let newX = self.position.x + self.driftSpeed
            let newY = self.position.y + self.driftSpeed
            
            if newX > maxX || newY > maxY {
                self.timer?.invalidate()
                self.timer = nil
            } else {
                withAnimation {
                    self.position = CGPoint(x: newX, y: newY)
                }
            }
        }
    }
}

struct ContentView: View {
    var body: some View {
        DriftingView()
    }
}

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