class GesturesConflictScrollView: UIScrollView {
  override func gestureRecognizerShouldBegin(_ gestureRecognizer: UIGestureRecognizer) -> Bool {
    back(by: gestureRecognizer)
  }

  private final func back(by gestureRecognizer: UIGestureRecognizer) -> Bool {
    
    guard gestureRecognizer == panGestureRecognizer else { return true }
    // point.x < 0 代表左滑即手指從屏幕右向左移動 反之一樣
    let point: CGPoint = panGestureRecognizer.translation(in: self)
    let state: UIGestureRecognizer.State = gestureRecognizer.state
    let locDistance: CGFloat = UIScreen.main.bounds.size.width
    
    if state == .began || state == .possible {
      let locationPoint = gestureRecognizer.location(in: self)
      if point.x > 0 && locationPoint.x < locDistance && contentOffset.x <= 0 {
        return false
      }
      let pageCount = contentSize.width / UIScreen.main.bounds.size.width
      let criticalPoint = pageCount < 2 ? locDistance : locDistance * (pageCount - 1)
      if point.x < 0 && contentOffset.x == criticalPoint {
        return false
      }
    }
    return true
  }
}