Swift：当键盘出现时向上移动UILabel

Question

我在找出键盘出现时如何移动UILabel时遇到问题。

目前，该标签从顶部位于大约140像素，当，当我使用模拟7 iPhone

但使用较小的iPhone 5时出现的键盘，我有这个问题坐镇完美中心。

其中键盘重叠的UILabel。

我想要做的是当键盘出现时将UILabel居中。

大多数教程都展示了如何移动UITextField，但我试图对UILabel应用相同的方面，但失败了。

Answer 1

当键盘出现时移动控件的一种可能的解决方案是向控件添加底部约束并为这些约束定义出口。

@IBOutlet weak var controlBottomConstraint: NSLayoutConstraint! 

在viewDidLoad注册keyboardWillShow方法中，当键盘出现像接收通知：

NotificationCenter.default.addObserver(self, selector: #selector(MyViewController.keyboardWillShow(_:)), name: NSNotification.Name.UIKeyboardWillShow, object: nil) 

然后在keyboardWillShow方法更新约束（controlBottomConstraint）所示：

func keyboardWillShow(_ notification:Notification) { 
    ... 
    let userInfo:NSDictionary = (notification as NSNotification).userInfo! as NSDictionary 
    let keyboardFrame:NSValue = userInfo.value(forKey: UIKeyboardFrameEndUserInfoKey) as! NSValue 
    let keyboardRectangle = keyboardFrame.cgRectValue 
    let keyboardHeight = keyboardRectangle.height 
    // controlBottomConstraint outlet to the control you want to move up 
    controlBottomConstraint.constant = keyboardHeight + 8 
} 

它也适用于旋转设备。

Answer 2

如果您正在进行约束，只需将乘数更改为0.5即可。如果您正在制作相框，请将相框的y位置（yourLabel.frame.origin.y）设置为self.view.frame.height/2。

Answer 3

尝试这个办法：一个延伸和补充通知观察家

class ViewController: UIViewController { 
    var keyboardOnScreen = false 

    @IBOutlet weak var searchBar: UISearchBar! 
    override func viewDidLoad() { 
     super.viewDidLoad() 

     NotificationCenter.default.addObserver(self, selector: #selector(keyboardWillShow), name:.UIKeyboardWillShow, object: nil) 
     NotificationCenter.default.addObserver(self, selector: #selector(keyboardWillHide), name: .UIKeyboardWillHide, object: nil) 
     NotificationCenter.default.addObserver(self, selector: #selector(keyboardDidShow), name: .UIKeyboardDidShow, object: nil) 
     NotificationCenter.default.addObserver(self, selector: #selector(keyboardDidHide), name: .UIKeyboardDidHide, object: nil) 

     searchBar.delegate = self 
    } 

} 
extension ViewController: UISearchBarDelegate { 

    func textFieldShouldReturn(_ textField: UITextField) -> Bool { 
     textField.resignFirstResponder() 
     return true 
    } 


    func keyboardWillShow(_ notification: Notification) { 
     if !keyboardOnScreen { 
      view.frame.origin.y -= keyboardHeight(notification)  } 
    } 

    func keyboardWillHide(_ notification: Notification) { 
     if keyboardOnScreen { 
      view.frame.origin.y += keyboardHeight(notification) 
     } 
    } 

    func keyboardDidShow(_ notification: Notification) { 
     keyboardOnScreen = true 
    } 

    func keyboardDidHide(_ notification: Notification) { 
     keyboardOnScreen = false 
    } 

    private func keyboardHeight(_ notification: Notification) -> CGFloat { 
     let userInfo = (notification as NSNotification).userInfo 
     let keyboardSize = userInfo![UIKeyboardFrameEndUserInfoKey] as! NSValue 
     return keyboardSize.cgRectValue.height 
    } 

    private func resignIfFirstResponder(_ textField: UITextField) { 
     if textField.isFirstResponder { 
      textField.resignFirstResponder() 
     } 
    } 

    @IBAction func userDidTapView(_ sender: AnyObject) { 
     resignIfFirstResponder(textField) 
    } 

    override func touchesBegan(_ touches: Set<UITouch>, with event: UIEvent?) { 
     self.view.endEditing(true) 
    } 

} 

Answer 4

第一的ViewController

import UIKit 

    class ViewController: UIViewController , UITableViewDelegate ,UITableViewDataSource, UITextViewDelegate { 

     @IBOutlet weak var ViewSend: UIView! 
     @IBOutlet weak var txtMessage: UITextView! 
     @IBOutlet weak var ChatTable: UITableView! 
     var chatArray:[String] = [] 
      var collect:String! 
     override func viewDidLoad() 
     { 
      super.viewDidLoad() 
      txtMessage.delegate = self 
      NotificationCenter.default.addObserver(self, selector: #selector(ViewController.keyboardWillShow), name: NSNotification.Name.UIKeyboardWillShow, object: nil) 
      NotificationCenter.default.addObserver(self, selector: #selector(ViewController.keyboardWillHide), name: NSNotification.Name.UIKeyboardWillHide, object: nil) 
      print(self.ViewSend.frame.origin.y) 

     } 
     override func didReceiveMemoryWarning() 
     { 
      super.didReceiveMemoryWarning() 
     } 
     func tableView(_ tableView: UITableView, numberOfRowsInSection section: Int) -> Int 
     { 
      return chatArray.count 
     } 
     func tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell { 
      let cell = tableView.dequeueReusableCell(withIdentifier: "CellDemo") as! chatlableTableViewCell 
      let obj = chatArray[indexPath.row] 
      cell.lblchat.text = obj 
      cell.lblchat.sizeToFit() 
      cell.lblchat.layer.cornerRadius = 2 
      cell.lblchat.clipsToBounds = true 
      return cell 
     } 


     @IBAction func btnSendPresssed(_ sender: UIButton) 
     { 
       if txtMessage.text == "" 
       { 

       } 
       else 
       { 

        collect = txtMessage.text 
        chatArray.append(collect) 
       } 
      ChatTable.reloadData() 
      txtMessage.text = "" 
     } 
     func calcheight(strin:String) -> CGFloat 
     { 
      let label = UILabel(frame: CGRect(x: 0, y: 0, width: UIScreen.main.bounds.size.width, height: CGFloat.greatestFiniteMagnitude)) 
      label.numberOfLines = 0 
      label.text = strin 
      label.sizeToFit() 
      return label.frame.height + 2 

     } 
     func tableView(_ tableView: UITableView, heightForRowAt indexPath: IndexPath) -> CGFloat 
     { 
      let height = self.calcheight(strin: String(describing: chatArray[indexPath.row])) 
      return height 

     } 
     func keyboardWillShow(notification: NSNotification) { 

      if let keyboardSize = (notification.userInfo?[UIKeyboardFrameBeginUserInfoKey] as? NSValue)?.cgRectValue 
      { 
       if self.ViewSend.frame.origin.y != keyboardSize.height 
       { 
        self.ViewSend.frame.origin.y -= keyboardSize.height 
        self.ChatTable.frame.size.height -= keyboardSize.height 
       } 
      } 
     } 
     func keyboardWillHide(notification: NSNotification) 
     { 

      if let keyboardSize = (notification.userInfo?[UIKeyboardFrameBeginUserInfoKey] as? NSValue)?.cgRectValue 
      { 
       self.ViewSend.frame.origin.y += keyboardSize.height 
      self.ChatTable.frame.size.height += (keyboardSize.height + ViewSend.frame.size.height) 

      } 

     } 

    } 

的TableView细胞

import UIKit 

class chatlableTableViewCell: UITableViewCell { 

    @IBOutlet weak var lblchat: UILabel! 
    override func awakeFromNib() { 
     super.awakeFromNib() 
     // Initialization code 
    } 

    override func setSelected(_ selected: Bool, animated: Bool) { 
     super.setSelected(selected, animated: animated) 

     // Configure the view for the selected state 
    } 

}