【发布时间】：2018-02-13 05:22:23
【问题描述】：
我正在尝试在按下按钮时添加 UILabels 和其他 UIView 元素，并让它们充当独立元素，但我没有运气。我可以成功添加多个标签和文本字段，但是当我尝试使用手势识别器删除它们时，它只会删除最新的 UIView 元素。我的完整代码发布在下面。我的实现中存在两个主要错误：一次创建多个标签或文本字段导致手势无响应，我只能删除最新的 UIView 元素。非常感谢任何帮助！
我的模特：
import Foundation
import UIKit
class QuizItem: UIViewController{
var alert = UIAlertController()
var labelCountStepper = 0
var tfCountStepper = 0
let gestureRecog = myLongPress(target: self, action: #selector(gestureRecognized(sender:)))
let moveGesture = myPanGesture(target: self, action: #selector(userDragged(gesture:)))
func createLabel(){
var randLabel = UILabel(frame: CGRect(x: 200, y: 200, width: 300, height: 20))
randLabel.isUserInteractionEnabled = true
randLabel.textColor = UIColor .black
randLabel.text = "I am a Test Label"
randLabel.tag = labelCountStepper
gestureRecog.quizItem = randLabel
moveGesture.quizItem = randLabel
randLabel.addGestureRecognizer(self.longPressGesture())
randLabel.addGestureRecognizer(self.movePanGesture())
topViewController()?.view.addSubview(randLabel)
labelCountStepper = labelCountStepper+1
}
func createTextField(){
var randTextField = UITextField(frame: CGRect(x: 200, y: 200, width: 300, height: 35))
randTextField.isUserInteractionEnabled = true
randTextField.backgroundColor = UIColor .lightGray
randTextField.placeholder = "Enter your message..."
randTextField.tag = tfCountStepper
gestureRecog.quizItem = randTextField
moveGesture.quizItem = randTextField
randTextField.addGestureRecognizer(self.longPressGesture())
randTextField.addGestureRecognizer(self.movePanGesture())
topViewController()?.view.addSubview(randTextField)
tfCountStepper = tfCountStepper+1
}
func longPressGesture() -> UILongPressGestureRecognizer {
let lpg = UILongPressGestureRecognizer(target: self, action: #selector(gestureRecognized(sender:)))
lpg.minimumPressDuration = 0.5
return lpg
}
func movePanGesture() -> UIPanGestureRecognizer {
let mpg = UIPanGestureRecognizer(target: self, action: #selector(userDragged(gesture:)))
return mpg
}
@objc func gestureRecognized(sender: UILongPressGestureRecognizer){
if(sender.state == .began){
print("Label Tag #: \(labelCountStepper)")
print("Text Field Tag #: \(tfCountStepper)")
alert = UIAlertController(title: "Remove Item?", message: nil, preferredStyle: .alert)
alert.addAction(UIAlertAction(title: "Yes", style: .default, handler: { (action) -> Void in
self.gestureRecog.quizItem.removeFromSuperview()
}))
alert.addAction(UIAlertAction(title: "No", style: .cancel){(_) in
})
topViewController()?.present(alert, animated: true, completion: nil)
}
}
@objc func userDragged(gesture: UIPanGestureRecognizer){
let loc = gesture.location(in: self.view)
moveGesture.quizItem.center = loc
}
override func viewDidLoad() {
super.viewDidLoad()
}
func topViewController() -> UIViewController? {
guard var topViewController = UIApplication.shared.keyWindow?.rootViewController else { return nil }
while topViewController.presentedViewController != nil {
topViewController = topViewController.presentedViewController!
}
return topViewController
}
}
我的视图控制器：
import UIKit
class ViewController: UIViewController {
var labelMaker = QuizItem()
@IBAction func createLabel(_ sender: UIButton) {
labelMaker.createLabel()
}
@IBAction func createTextField(_ sender: UIButton) {
labelMaker.createTextField()
}
override func viewDidLoad() {
}
override func didReceiveMemoryWarning() {
super.didReceiveMemoryWarning()
}
}
我还创建了两个继承自 UILongPress 和 UIPan 手势识别器的子类。我只会发布 LongPress，因为 UIPan 完全相同 - 只是继承自 UIPan 而不是 UILongPress。
import Foundation
import UIKit
class myLongPress: UILongPressGestureRecognizer{
var quizItem = UIView()
}
【问题讨论】：
-
每次设置gestureRecog.quizItem 即gestureRecog.quizItem = randLabel 的quizitem 都会被替换，如果你调用gestureRecog.quizItem = randTextField，那么quizitem 就会变成文本字段
-
您没有实例化 QuizItem 来创建对象。您只是在调用 QuizItem 及其函数。