手势识别器
当您将Gesture Recognizer 添加到您的视图时，可以通知您一些常用的触摸事件（或手势）。默认支持以下手势类型：
-
UITapGestureRecognizer 点击（短按屏幕一次或多次）
-
UILongPressGestureRecognizer长按（长时间触摸屏幕）
-
UIPanGestureRecognizer Pan（在屏幕上移动手指）
-
UISwipeGestureRecognizer 滑动（快速移动手指）
-
UIPinchGestureRecognizer 捏合（将两根手指合拢或分开——通常用于缩放）
-
UIRotationGestureRecognizer 旋转（两个手指在圆周方向移动）
除此之外，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您的视图中。
控制从文档大纲中的手势拖动到您的视图控制器代码，以制作一个 Outlet 和一个动作。
这应该默认设置，但也要确保 User Action Enabled 为您的视图设置为 true。
以编程方式添加手势
要以编程方式添加手势，您 (1) 创建手势识别器，(2) 将其添加到视图中，以及 (3) 创建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")
}
}
备注
-
sender 参数是可选的。如果您不需要对手势的引用，则可以将其省略。但是，如果您这样做，请删除操作方法名称后的 (sender:)。
-
handleTap 方法的命名是任意的。使用 action: #selector(<strong>someMethodName</strong>(sender:)) 随意命名。
更多示例
您可以研究我添加到这些视图中的手势识别器，看看它们是如何工作的。
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
}
}
}
备注
- 您可以将多个手势识别器添加到单个视图中。不过，为了简单起见，我没有这样做（滑动手势除外）。如果你的项目需要，你应该阅读gesture recognizer documentation。这很容易理解，也很有帮助。
- 上述示例的已知问题：(1) 平移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来自错误的方向。 （不过，我的示例中的这些错误不会影响您对手势识别器工作原理的理解。）