UILabel有什麼價值可供選擇嗎？

Question

UILabel是否有任何值可以設置，以使其可選？

我有一個標籤，我想可以選擇，（長按和複製btn顯示）有點像在Safari中。

Answer 1

是的，您需要通過應用於您的UILabel的長按手勢來實現UIMenuController。有關於NSHipster的優秀文章，但文章的要點如下。

創建的UILabel的一個子類，並實現以下方法：

override func canBecomeFirstResponder() -> Bool { 
    return true 
} 

override func canPerformAction(action: Selector, withSender sender: AnyObject?) -> Bool { 
    return (action == "copy:") 
} 

// MARK: - UIResponderStandardEditActions 

override func copy(sender: AnyObject?) { 
    UIPasteboard.generalPasteboard().string = text 
} 

然後在您的視圖控制器，你可以添加一個長按手勢您的標籤：

let gestureRecognizer = UILongPressGestureRecognizer(target: self, action: "handleLongPressGesture:") 
label.addGestureRecognizer(gestureRecognizer) 

和處理長用此方法按下：

func handleLongPressGesture(recognizer: UIGestureRecognizer) { 
    if let recognizerView = recognizer.view, 
     recognizerSuperView = recognizerView.superview 
    { 
     let menuController = UIMenuController.sharedMenuController() 
     menuController.setTargetRect(recognizerView.frame, inView: recognizerSuperView) 
     menuController.setMenuVisible(true, animated:true) 
     recognizerView.becomeFirstResponder() 
    }} 

注意：此代碼直接從t他NSHipster的文章，我只是在這裏包括它符合SO。

Answer 2

UILabel從UIView繼承，因此您只需將長按手勢識別器添加到標籤即可。請注意，您必須將isUserInteractionEnabled更改爲true，因爲它對於標籤默認爲false。

import UIKit 

    class ViewController: UIViewController { 
     let label = UILabel() 

     override func viewDidLoad() { 
      view.addSubview(label) 
      label.text = "hello" 
      label.translatesAutoresizingMaskIntoConstraints = false 
      label.centerXAnchor.constraint(equalTo: view.centerXAnchor).isActive = true 
      label.centerYAnchor.constraint(equalTo: view.centerYAnchor).isActive = true 
      let longPressGestureRecognizer = UILongPressGestureRecognizer(target: self, action: #selector(longPressLabel(longPressGestureRecognizer:))) 
      label.addGestureRecognizer(longPressGestureRecognizer) 
      label.isUserInteractionEnabled = true 
     } 

     @objc private func longPressLabel (longPressGestureRecognizer: UILongPressGestureRecognizer) { 
      if longPressGestureRecognizer.state == .began { 
       print("long press began") 
      } else if longPressGestureRecognizer.state == .ended { 
       print("long press ended") 
      } 

     } 

    } 

Answer 3

我已經實現了一個UILabel子類，它提供了所需的所有功能。請注意，如果您將此與界面構建器配合使用，則需要調整init方法。

/// A label that can be copied. 
class CopyableLabel: UILabel 
{ 
    // MARK: - Initialisation 

    /// Creates a new label. 
    init() 
    { 
     super.init(frame: .zero) 

     let gestureRecognizer = UILongPressGestureRecognizer(target: self, action: #selector(handleLongPressGesture(_:))) 
     self.addGestureRecognizer(gestureRecognizer) 

     self.isUserInteractionEnabled = true 
    } 

    required init?(coder aDecoder: NSCoder) 
    { 
     fatalError("init(coder:) has not been implemented") 
    } 

    // MARK: - Responder chain 

    override var canBecomeFirstResponder: Bool 
    { 
     return true 
    } 

    // MARK: - Actions 

    /// Method called when a long press is triggered. 
    func handleLongPressGesture(_ gestuerRecognizer: UILongPressGestureRecognizer) 
    { 
     guard let superview = self.superview else { return } 

     let menuController = UIMenuController.shared 
     menuController.setTargetRect(self.frame, in: superview) 
     menuController.setMenuVisible(true, animated:true) 
     self.becomeFirstResponder() 
    } 

    override func copy(_ sender: Any?) 
    { 
     UIPasteboard.general.string = self.text 
    } 
}