iOS手势处理由UIGestureRecognizer控制，不同手势有这个类的不同子类处理，不同手势处理有不同的相关属性。

手势处理的步骤一般：

1. 初始化手势，并添加到需要手势的View中
2. 添加手势回调方法

UITapGestureRecognizer

属性numberOfTapsRequired表示点击次数，属性numberOfTouchesRequired表示点击手指数。

var isChange = false
...
let tap = UITapGestureRecognizer(target: self, action: #selector(ViewController.tap(tap:)))
tap.numberOfTapsRequired = 2
...
imageView.addGestureRecognizer(tap)
...

@objc func tap(tap: UITapGestureRecognizer) {
    let center = imageView.center
    if isChange {
        imageView.frame.size.width /= 2
        imageView.frame.size.height /= 2
        imageView.center = center
        isChange = false
    } else {
        imageView.frame.size.width *= 2
        imageView.frame.size.height *= 2
        imageView.center = center
        isChange = true
    }
}

UIPanGestureRecognizer

let pan = UIPanGestureRecognizer(target: self, action: #selector(ViewController.pan(pan:)))

    @objc func pan(pan: UIPanGestureRecognizer) {
        if pan.state == .began || pan.state == .changed {
            // 移动后的变化（变化值类似向量）
            let translation = pan.translation(in: imageView.superview)
            print(translation)
            imageView.center = CGPoint(x: imageView.center.x + translation.x, y: imageView.center.y  + translation.y)
            // view移动后，把上一步的移动值变为0，否则移动值为递增
            pan.setTranslation(CGPoint.zero, in: imageView.superview)
        }
    }

UIRotationGestureRecognizer

    let rotation = UIRotationGestureRecognizer(target: self, action: #selector(ViewController.rotation(rotation:)))

    @objc func rotation(rotation: UIRotationGestureRecognizer) {
        if rotation.state == .began || rotation.state == .changed {
            imageView.transform = CGAffineTransform(rotationAngle: rotation.rotation)
        }
    }

UISwipeGestureRecognizer

    let swipe = UISwipeGestureRecognizer(target: self, action: #selector(ViewController.swipe(swipe:)))
    swipe.direction = .up
    swipe.numberOfTouchesRequired = 3

    @objc func swipe(swipe: UISwipeGestureRecognizer) {
        print("扫的方向：\(swipe.direction),扫的手指数：\(swipe.numberOfTouchesRequired)")
    }

UILongPressGestureRecognizer

numberOfTouchesRequired 长按的指头数
minimumPressDuratio 长按最小时间（秒）

    let long = UILongPressGestureRecognizer(target: self, action: #selector(ViewController.long(long:)))
    long.numberOfTouchesRequired = 2
    long.minimumPressDuration = 1

    @objc func long(long: UILongPressGestureRecognizer) {
        print("长按手势，长按字头数为\(long.numberOfTouchesRequired)")
    }

UIScreenEdgePanGestureRecognizer

    let screenEdge = UIScreenEdgePanGestureRecognizer(target: self, action: #selector(ViewController.screenEdage(screenEdage:)))
    screenEdge.edges = .left

    @objc func screenEdage(screenEdage: UIScreenEdgePanGestureRecognizer) {
        print("屏幕边缘滑动手势：\(screenEdage.edges)")
    }

详细代码： GestureDemo