键盘出现时更改约束-SWIFT-移动开发问题

Changing Constraint when Keyboard Appears - Swift(键盘出现时更改约束-SWIFT)

本文介绍了键盘出现时更改约束-SWIFT的处理方法，对大家解决问题具有一定的参考价值，需要的朋友们下面随着小编来一起学习吧！

问题描述

我的UIView在键盘出现时无法正常移动。UIView中有一个UITextView，我用它来输入文本。如果我选择TextView来输入文本，键盘会出现，但UIView第一次不会移动。如果我轻触背景并使键盘消失，然后再次轻触TextView，则UIView会正确上移。有人知道这里发生了什么事吗？

class ChatViewController: UIViewController, CNContactPickerDelegate, UISearchBarDelegate, UITableViewDelegate, UITableViewDataSource, UIToolbarDelegate, UITextFieldDelegate, UITextViewDelegate {

@IBOutlet weak var composeTextView: UITextView!

@IBOutlet weak var composeViewBottomConstraint: NSLayoutConstraint!

override func viewDidLoad() {
    super.viewDidLoad()

    composeTextView.delegate = self

}

func textViewDidBeginEditing(_ textView: UITextView) {

    UIView.animate(withDuration: 0.5){
        NotificationCenter.default.addObserver(self, selector: #selector(self.keyboardWillShow), name: .UIKeyboardWillShow, object: nil)

    }

    self.view.layoutIfNeeded()


}

@objc func keyboardWillShow(notification: Notification) {
    let keyboardSize = (notification.userInfo?[UIKeyboardFrameEndUserInfoKey] as? NSValue)?.cgRectValue

    let keyboardHeight = keyboardSize?.height

        if #available(iOS 11.0, *){

            self.composeViewBottomConstraint.constant = keyboardHeight! - view.safeAreaInsets.bottom
        }
        else {
            self.composeViewBottomConstraint.constant = view.safeAreaInsets.bottom
        }
        self.view.layoutIfNeeded()

}

}

推荐答案

问题是，第一次单击textView没有向上的视图是在BeginEditing中添加了showKeyboard观察器，所以该行应该在viewDidLoad

中

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

除以下修复外

func textViewDidBeginEditing(_ textView: UITextView) {

     // I think no need for it

}

 @objc func keyboardWillShow(notification: Notification) {

     let keyboardSize = (notification.userInfo?  [UIKeyboardFrameEndUserInfoKey] as? NSValue)?.cgRectValue

     let keyboardHeight = keyboardSize?.height

     if #available(iOS 11.0, *){

          self.composeViewBottomConstraint.constant = keyboardHeight! - view.safeAreaInsets.bottom
      }
      else {
           self.composeViewBottomConstraint.constant = view.safeAreaInsets.bottom
         }

       UIView.animate(withDuration: 0.5){

          self.view.layoutIfNeeded()

       }


   }

  @objc func keyboardWillHide(notification: Notification){

      self.composeViewBottomConstraint.constant =  0 // or change according to your logic  

       UIView.animate(withDuration: 0.5){

          self.view.layoutIfNeeded()

       }

  }

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