手势识别器
将手势识别器添加到视图时，可以通知许多常用的触摸事件（或手势）。默认情况下支持以下手势类型：
UITapGestureRecognizer 点按（短暂触摸屏幕一次或多次）UILongPressGestureRecognizer 长按（长时间触摸屏幕）UIPanGestureRecognizer 平移（在屏幕上移动手指）UISwipeGestureRecognizer 滑动（快速移动手指）UIPinchGestureRecognizer 捏（将两个手指并拢或分开移动-通常进行缩放）UIRotationGestureRecognizer 旋转（沿圆周方向移动两个手指）
除了这些，您还可以制作自己的自定义手势识别器。
在界面生成器中添加手势
将手势识别器从对象库拖到视图上。
控制从Document Outline中的手势拖到View Controller代码中，以创建一个Outlet和一个Action。
默认情况下应设置此选项，但还应确保您的视图的“启用用户操作”设置为true。
以编程方式添加手势
要以编程方式添加手势，您（1）创建一个手势识别器，（2）将其添加到视图中，以及（3）制作一个在识别手势时调用的方法。
import UIKit
class ViewController: UIViewController {
@IBOutlet weak var myView: UIView!
override func viewDidLoad() {
super.viewDidLoad()
// 1. create a gesture recognizer (tap gesture)
let tapGesture = UITapGestureRecognizer(target: self, action: #selector(handleTap(sender:)))
// 2. add the gesture recognizer to a view
myView.addGestureRecognizer(tapGesture)
}
// 3. this method is called when a tap is recognized
@objc func handleTap(sender: UITapGestureRecognizer) {
print("tap")
}
}
笔记
- 该
sender参数是可选的。如果不需要引用手势，则可以将其省略。但是，如果这样做，请删除(sender:)操作方法名称之后的。
- 该
handleTap方法的命名是任意的。命名为任何您想使用的。action: #selector(someMethodName(sender:))
更多例子
您可以研究我添加到这些视图中的手势识别器，以了解它们的工作原理。
这是该项目的代码：
import UIKit
class ViewController: UIViewController {
@IBOutlet weak var tapView: UIView!
@IBOutlet weak var doubleTapView: UIView!
@IBOutlet weak var longPressView: UIView!
@IBOutlet weak var panView: UIView!
@IBOutlet weak var swipeView: UIView!
@IBOutlet weak var pinchView: UIView!
@IBOutlet weak var rotateView: UIView!
@IBOutlet weak var label: UILabel!
override func viewDidLoad() {
super.viewDidLoad()
// Tap
let tapGesture = UITapGestureRecognizer(target: self, action: #selector(handleTap))
tapView.addGestureRecognizer(tapGesture)
// Double Tap
let doubleTapGesture = UITapGestureRecognizer(target: self, action: #selector(handleDoubleTap))
doubleTapGesture.numberOfTapsRequired = 2
doubleTapView.addGestureRecognizer(doubleTapGesture)
// Long Press
let longPressGesture = UILongPressGestureRecognizer(target: self, action: #selector(handleLongPress(gesture:)))
longPressView.addGestureRecognizer(longPressGesture)
// Pan
let panGesture = UIPanGestureRecognizer(target: self, action: #selector(handlePan(gesture:)))
panView.addGestureRecognizer(panGesture)
// Swipe (right and left)
let swipeRightGesture = UISwipeGestureRecognizer(target: self, action: #selector(handleSwipe(gesture:)))
let swipeLeftGesture = UISwipeGestureRecognizer(target: self, action: #selector(handleSwipe(gesture:)))
swipeRightGesture.direction = UISwipeGestureRecognizerDirection.right
swipeLeftGesture.direction = UISwipeGestureRecognizerDirection.left
swipeView.addGestureRecognizer(swipeRightGesture)
swipeView.addGestureRecognizer(swipeLeftGesture)
// Pinch
let pinchGesture = UIPinchGestureRecognizer(target: self, action: #selector(handlePinch(gesture:)))
pinchView.addGestureRecognizer(pinchGesture)
// Rotate
let rotateGesture = UIRotationGestureRecognizer(target: self, action: #selector(handleRotate(gesture:)))
rotateView.addGestureRecognizer(rotateGesture)
}
// Tap action
@objc func handleTap() {
label.text = "Tap recognized"
// example task: change background color
if tapView.backgroundColor == UIColor.blue {
tapView.backgroundColor = UIColor.red
} else {
tapView.backgroundColor = UIColor.blue
}
}
// Double tap action
@objc func handleDoubleTap() {
label.text = "Double tap recognized"
// example task: change background color
if doubleTapView.backgroundColor == UIColor.yellow {
doubleTapView.backgroundColor = UIColor.green
} else {
doubleTapView.backgroundColor = UIColor.yellow
}
}
// Long press action
@objc func handleLongPress(gesture: UILongPressGestureRecognizer) {
label.text = "Long press recognized"
// example task: show an alert
if gesture.state == UIGestureRecognizerState.began {
let alert = UIAlertController(title: "Long Press", message: "Can I help you?", preferredStyle: UIAlertControllerStyle.alert)
alert.addAction(UIAlertAction(title: "OK", style: UIAlertActionStyle.default, handler: nil))
self.present(alert, animated: true, completion: nil)
}
}
// Pan action
@objc func handlePan(gesture: UIPanGestureRecognizer) {
label.text = "Pan recognized"
// example task: drag view
let location = gesture.location(in: view) // root view
panView.center = location
}
// Swipe action
@objc func handleSwipe(gesture: UISwipeGestureRecognizer) {
label.text = "Swipe recognized"
// example task: animate view off screen
let originalLocation = swipeView.center
if gesture.direction == UISwipeGestureRecognizerDirection.right {
UIView.animate(withDuration: 0.5, animations: {
self.swipeView.center.x += self.view.bounds.width
}, completion: { (value: Bool) in
self.swipeView.center = originalLocation
})
} else if gesture.direction == UISwipeGestureRecognizerDirection.left {
UIView.animate(withDuration: 0.5, animations: {
self.swipeView.center.x -= self.view.bounds.width
}, completion: { (value: Bool) in
self.swipeView.center = originalLocation
})
}
}
// Pinch action
@objc func handlePinch(gesture: UIPinchGestureRecognizer) {
label.text = "Pinch recognized"
if gesture.state == UIGestureRecognizerState.changed {
let transform = CGAffineTransform(scaleX: gesture.scale, y: gesture.scale)
pinchView.transform = transform
}
}
// Rotate action
@objc func handleRotate(gesture: UIRotationGestureRecognizer) {
label.text = "Rotate recognized"
if gesture.state == UIGestureRecognizerState.changed {
let transform = CGAffineTransform(rotationAngle: gesture.rotation)
rotateView.transform = transform
}
}
}
笔记
- 您可以将多个手势识别器添加到单个视图。但是，为了简单起见，我没有这样做（除了滑动手势）。如果需要用于项目，则应阅读手势识别器文档。这是相当容易理解和有用的。
- 我上面的示例的已知问题：（1）全景视图在下一个手势事件时重置其框架。（2）滑动视图在第一次滑动时方向错误。（不过，我示例中的这些错误不应影响您对手势识别器工作原理的理解。）
