ios - 翻译时仅运行一次 swift 条件

Question

我创建了一个UIView和一个UIImageView，它位于UIView内部作为 subview ，然后我向添加了一个平移手势>UIImageView 在 UIView 内滑动，图像现在滑动，但我现在遇到的问题是当 slider 到达 View 末尾时if movex > xMax，我只想打印一次 print("SWIPPERD movex")。只要用户不将他/她的手从用于滑动的 UIImageView 上移开，我当前的代码就会继续打印 print("SWIPPERD movex")

private func swipeFunc() {

    let swipeGesture = UIPanGestureRecognizer(target: self, action: #selector(acknowledgeSwiped(sender:)))
    sliderImage.addGestureRecognizer(swipeGesture)
    swipeGesture.delegate = self as? UIGestureRecognizerDelegate
}

@objc func acknowledgeSwiped(sender: UIPanGestureRecognizer) {
    if let sliderView = sender.view {
        let translation = sender.translation(in: self.baseView) //self.sliderView
        switch sender.state {
        case .began:
            startingFrame = sliderImage.frame
            viewCenter = baseView.center
            fallthrough
        case .changed:
            if let startFrame = startingFrame  {

                var movex = translation.x
                if movex < -startFrame.origin.x {
                    movex = -startFrame.origin.x
                    print("SWIPPERD minmax")
                }

                let xMax = self.baseView.frame.width - startFrame.origin.x - startFrame.width - 15 //self.sliderView
                if movex > xMax {
                    movex = xMax
                    print("SWIPPERD movex")
                }

                var movey = translation.y
                if movey < -startFrame.origin.y { movey = -startFrame.origin.y }

                let yMax = self.baseView.frame.height - startFrame.origin.y - startFrame.height //self.sliderView
                if movey > yMax {
                    movey = yMax
                    //                        print("SWIPPERD min")
                }

                sliderView.transform = CGAffineTransform(translationX: movex, y: movey)
            }
        default: // .ended and others:
            UIView.animate(withDuration: 0.1, animations: {
                sliderView.transform = CGAffineTransform.identity
            })
        }
    }
}


override func point(inside point: CGPoint, with event: UIEvent?) -> Bool {
    return sliderImage.frame.contains(point)
}

Answer 1

根据您的要求，您可能希望使用 .ending 状态而不是 .changed 状态。你也提到过你只想得到正确的方向。您可以尝试以下方法来确定滑动是否从右向左，反之亦然，根据您的意愿进行更改:

let velocity = sender.velocity(in: sender.view)
let rightToLeftSwipe = velocity.x < 0