一 、UIGestureRecognizer 介绍

手势识别在 iOS 中非常重要，他极大地提高了移动设备的使用便捷性。iOS 系统在 3.2 以后，他提供了一些常用的手势（UIGestureRecognizer 的子类），开发者可以直接使用他们进行手势操作。
UIGestureRecognizer 的子类如下：
UIPanGestureRecognizer（拖动） 、 UIPinchGestureRecognizer（捏合） 、UIRotationGestureRecognizer（旋转）、UITapGestureRecognizer（点按） 、 UILongPressGestureRecognizer（长按）、 ​UISwipeGestureRecognizer（轻扫）

二、上述各个手势的介绍

1、UITapGestureRecognizer 的介绍

// MARK :UITapGestureRecognizer 的介绍
func introduceTapGestureRecognizer() {
    // 初始化
    let NwTapGestureRecongnizer = UITapGestureRecognizer.init(target: self, action: #selector(tapGestureClick))
    // 点击几次触发事件
    NwTapGestureRecongnizer.numberOfTapsRequired = 2
    // 几根手指点击触发事件
    NwTapGestureRecongnizer.numberOfTouchesRequired = 2
    // 手势的添加
    NwImageView.addGestureRecognizer(NwTapGestureRecongnizer)
}
// TODO : tapGestureClick 的事件
func tapGestureClick() -> Void {
    print("被点击了")
}

2 、UIPinchGestureRecognizer 捏合手势的介绍

// MARK : UIPinchGestureRecognizer 捏合手势的介绍
func introducePinchGestureRecognizer() -> Void {
     // 初始化
    let NwPinchGestureRecognizer = UIPinchGestureRecognizer.init(target: self, action: #selector(pinchGestureClick(_ :)))
    // 设置缩放比值
    NwPinchGestureRecognizer.scale = 2
    // 手势添加
    NwImageView.addGestureRecognizer(NwPinchGestureRecognizer)
}
// TODO : pinchGestureClick 的事件
func pinchGestureClick(_ pinchGesture : UIPinchGestureRecognizer) -> Void {
    // 获取缩放比率
    let velocityValue = pinchGesture.velocity
    print("我的捏合速率是" + "\(velocityValue)")
}

3 、 UILongPressGestureRecognizer 长按手势的介绍

// MARK : UILongPressGestureRecognizer 长按手势的介绍
func introduceLongPressGestureRecognizer() -> Void {
    // 初始化
    let NwLongPressGestureRecognizer = UILongPressGestureRecognizer.init(target: self, action: #selector(longPressGestureClick))
    // 设置几次长按触发事件
    NwLongPressGestureRecognizer.numberOfTapsRequired = 2
    // 设置几个手指长按
    NwLongPressGestureRecognizer.numberOfTouchesRequired = 2
    // 设置长按的时间间隔
    NwLongPressGestureRecognizer.minimumPressDuration = 0.4
    // 设置长按期间可移动的距离
    NwLongPressGestureRecognizer.allowableMovement = 20
    // 添加手势
    NwImageView.addGestureRecognizer(NwLongPressGestureRecognizer)
}
// TODO : longPressGestureClick 
func longPressGestureClick() -> Void {
    print("长按手势点击")
}

4 、UISwipeGestureRecognizer 清扫手势

// MARK : UISwipeGestureRecognizer  清扫手势
func introduceSwipeGestureRecognizer() -> Void {
    // 初始化
    let NwSwipeGestureRecognizer = UISwipeGestureRecognizer.init(target: self, action: #selector(swipeGestureClick))
    // 设置几个手指轻扫触发
    NwSwipeGestureRecognizer.numberOfTouchesRequired = 2
    /**
     设置轻扫的方向
     UISwipeGestureRecognizerDirection 方向
     left : 向左
     right :向右
     up : 向上
     down : 向下
     */
    NwSwipeGestureRecognizer.direction = .left
    // 添加手势
    NwImageView.addGestureRecognizer(NwSwipeGestureRecognizer)
}
func swipeGestureClick() -> Void {
    print("轻扫触发")
    
}

5、UIPanGestureRecognizer 拖拽手势

    // MARK : UIPanGestureRecognizer 拖拽手势
    
    func introducePanGestureRecognizer() -> Void {
         // 初始化
        let NwPanGestureRecognizer = UIPanGestureRecognizer.init(target: self, action: #selector(panGestureClick(_ :)))
        // 设置最多几个手指和最少几个手指触发
        NwPanGestureRecognizer.maximumNumberOfTouches = 2
        NwPanGestureRecognizer.minimumNumberOfTouches = 1
        // 设置将某个对象拖拽到那个点
        NwPanGestureRecognizer.setTranslation(CGPoint.init(x: 100, y: 100), in: NwImageView)
        // 添加手势
        NwImageView.addGestureRecognizer(NwPanGestureRecognizer)
    }
    // TODO : panGestureClick 拖拽手势
    func panGestureClick(_ panGesture:UIPanGestureRecognizer) -> Void {
        // 获取用户拖拽的点
        let panPoint =  panGesture.translation(in: NwImageView)
        print(panPoint.x + panPoint.y)
        // 获取拖拽速率
        let panVelocity = panGesture.velocity(in: NwImageView)
        print(panVelocity)
        
    }

6 、UIRotationGestureRecognizer 旋转手势

// MARK : UIRotationGestureRecognizer 旋转手势
func introduceRotationGestureRecognizer() -> Void {
     // 初始化
    let NwRotationGestureRecognizer = UIRotationGestureRecognizer.init(target: self, action: #selector(rotationGestureClick(_ :)))
    // 设置旋转的弧度
    NwRotationGestureRecognizer.rotation = 2
    // 添加手势
    NwImageView.addGestureRecognizer(NwRotationGestureRecognizer)
}
// TODO : rotationGestureClick 旋转手势的触发
func rotationGestureClick(_ rotationGesture:UIRotationGestureRecognizer) -> Void {
    let rotationVelocity = rotationGesture.velocity
    print(rotationVelocity)
}

三 、手势的代理

// MARK : 各个手势的代理事件
// TODO : 控制是否允许手势的触发
func gestureRecognizerShouldBegin(_ gestureRecognizer: UIGestureRecognizer) -> Bool {
     return true
}

// TODO : 是否允许多个手势同时触发
func gestureRecognizer(_ gestureRecognizer: UIGestureRecognizer, shouldRecognizeSimultaneouslyWith otherGestureRecognizer: UIGestureRecognizer) -> Bool {
     return true
}

// TODO : 两个手势挥斥的时候，第一个失效，执行第二个
func gestureRecognizer(_ gestureRecognizer: UIGestureRecognizer, shouldBeRequiredToFailBy otherGestureRecognizer: UIGestureRecognizer) -> Bool {
     return true
}

// TODO : 两个手势挥斥的时候，第一个执行，第二个失效
func gestureRecognizer(_ gestureRecognizer: UIGestureRecognizer, shouldRequireFailureOf otherGestureRecognizer: UIGestureRecognizer) -> Bool {
     return true
}

// TODO : 手指触摸屏幕，开始手势的识别
func gestureRecognizer(_ gestureRecognizer: UIGestureRecognizer, shouldReceive touch: UITouch) -> Bool {
     return true
}

// TODO : 手指触摸屏幕，开始手势的识别
func gestureRecognizer(_ gestureRecognizer: UIGestureRecognizer, shouldReceive press: UIPress) -> Bool {
    return true
}