无需触摸手动启动 UIPanGestureRecognizer

Question

我有一个不覆盖整个屏幕的表格视图（它有点像屏幕底部的抽屉）。当用户向下滚动到内容的末尾时，我想停止滚动，然后添加一个平移手势识别器。我是这样做的：

// MARK: UIScrollViewDelegate Methods

extension TutorProfileVC: UIScrollViewDelegate {

    func scrollViewDidScroll(_ scrollView: UIScrollView) {
        // Limit top vert bounce
        guard mode == .drawer else { return }
        if scrollView.contentOffset.y < -80.0 {
            scrollView.contentOffset = CGPoint(x: 0, y: -80.0)
            tableView.addGestureRecognizer(tablePanGR)
        }
    }

}

手势已添加，但在用户再次触摸屏幕之前不会注册。他们的手指已经在桌面视图上。是否可以在无需再次触摸屏幕的情况下启动手势？

Answer 1

我认为您对this question 有同样的问题。如果您想查看代码示例，请查看它。

要解决问题，您应该从头开始添加手势，但仅在用户滚动到底部时处理手势动作。因此，您无需再次触摸屏幕，因为手势在您开始滚动时就开始了。处理手势的方法如下所示

@objc func handlePanGestureRecognizer(_ gestureRecognizer: UIPanGestureRecognizer) {
  switch gestureRecognizer.state {
  case .began:
    // Do nothing
    break
  case .changed:
    let translation    = gestureRecognizer.translation(in: gestureRecognizer.view!.superview!)
    let velocity    = gestureRecognizer.velocity(in: gestureRecognizer.view!.superview)
    let state      = gestureRecognizer.state

    // Don't do anything until |scrollView| reached bottom
    if scrollView.contentOffset.y >= -80.0 {
      return;
    }

    // Do whatever you want with |scrollView|
    }
    break;
  case .cancelled:
  case .ended:
  case .failed:
  default:
    break;
  }
}

同时实现gestureRecognizer:shouldRecognizeSimultaneouslyWithGestureRecognizer: 以使手势和滚动视图协同工作

func gestureRecognizer(_ gestureRecognizer: UIGestureRecognizer, shouldRecognizeSimultaneouslyWith otherGestureRecognizer: UIGestureRecognizer) -> Bool {
  return true
}