在选择文本字段时，调整键盘的视图高度

Question

我在 xib 中有一个 ViewController（登录视图），它有 2 个 UITextField 和 1 个 UIButton 组件。视图层次结构是

 UIView
     -> UIScrollView
         -> UIView (contentView)
             -> UITextField
             -> UITextField
             -> UIButton

我正在为视图使用自动布局。 UIScrollView 有 4 个约束，即前导、尾随、顶部和底部与其父视图（UIViewController 视图）对齐。 ContentView 有 4 个约束，即其父视图 (UIScrollView) 的前导、尾随、顶部和底部以及宽度匹配 UIViewController 视图。

当用户选择UITextField 时，我已按照Apple documentation 中的步骤向上或向下滚动，以便键盘不在UITextField 之上。

当显示键盘时，scrollview 向上滚动，但当键盘隐藏时，scrollview 不会向后滚动。任何帮助表示赞赏。

override func viewDidLoad() {
    NotificationCenter.default.addObserver(self, selector: #selector(keyboardWillShow), name: NSNotification.Name.UIKeyboardWillShow, object: nil)
    NotificationCenter.default.addObserver(self, selector: #selector(keyboardWillHide), name: NSNotification.Name.UIKeyboardWillHide, object: nil)
}

func keyboardWillHide(notification: NSNotification) {

        let contentInsets: UIEdgeInsets = UIEdgeInsets.zero
        self.scrollView.contentInset = contentInsets
        self.scrollView.scrollIndicatorInsets = contentInsets
    } 

func keyboardWillShow(notification: NSNotification) {

        if let activeField = self.activeField, let keyboardSize = (notification.userInfo?[UIKeyboardFrameBeginUserInfoKey] as? NSValue)?.cgRectValue {

            let contentInsets = UIEdgeInsets(top: 0.0, left: 0.0, bottom: keyboardSize.height, right: 0.0)

            self.scrollView.contentInset = contentInsets
            self.scrollView.scrollIndicatorInsets = contentInsets

            var aRect = self.view.frame

            aRect.size.height -= keyboardSize.size.height
            if (!aRect.contains(activeField.frame.origin)) {
                self.scrollView.scrollRectToVisible(activeField.frame, animated: true)
            }
        }
    }

Answer 1

滚动视图contentInset.top 不是0.0，因此我遇到了问题。更改 contentInset.top 后，正确地将滚动视图设置为隐藏键盘后的原始位置。

func keyboardWillShow(notification: NSNotification) {

        self.scrollView.isScrollEnabled = true

        var info = notification.userInfo!
        let keyboardSize = (info[UIKeyboardFrameBeginUserInfoKey] as? NSValue)?.cgRectValue.size
        let contentInsets : UIEdgeInsets = UIEdgeInsetsMake(self.scrollView.contentInset.top, 0.0, keyboardSize!.height, 0.0)

        self.scrollView.contentInset = contentInsets
        self.scrollView.scrollIndicatorInsets = contentInsets

        var aRect : CGRect = self.view.frame
        aRect.size.height -= keyboardSize!.height
        if let activeField = self.activeField {
            if (!aRect.contains(activeField.frame.origin)){
                self.scrollView.scrollRectToVisible(activeField.frame, animated: true)
            }
        }
    }

Answer 2

这个键盘问题在苹果文档中有详细解释：

https://developer.apple.com/library/content/documentation/StringsTextFonts/Conceptual/TextAndWebiPhoneOS/KeyboardManagement/KeyboardManagement.html

或者，试试下面的代码：

func registerForKeyboardNotifications(){
    NotificationCenter.default.addObserver(self, selector: #selector(keyboardWasShown(notification:)), name:       NSNotification.Name.UIKeyboardWillShow, object: nil)
    NotificationCenter.default.addObserver(self, selector: #selector(keyboardWillBeHidden(notification:)), name:    NSNotification.Name.UIKeyboardWillHide, object: nil)
}

func deregisterFromKeyboardNotifications(){
   NotificationCenter.default.removeObserver(self, name: NSNotification.Name.UIKeyboardWillShow, object: nil)
   NotificationCenter.default.removeObserver(self, name: NSNotification.Name.UIKeyboardWillHide, object: nil)
}

func keyboardWasShown(notification: NSNotification){
   self.scrollView.isScrollEnabled = true
   var info = notification.userInfo!
   let keyboardSize = (info[UIKeyboardFrameBeginUserInfoKey] as? NSValue)?.cgRectValue.size
   let contentInsets : UIEdgeInsets = UIEdgeInsetsMake(0.0, 0.0, keyboardSize!.height, 0.0)

   self.scrollView.contentInset = contentInsets
   self.scrollView.scrollIndicatorInsets = contentInsets

   var aRect : CGRect = self.view.frame
   aRect.size.height -= keyboardSize!.height
   if let activeField = self.activeField {
       if (!aRect.contains(activeField.frame.origin)){
           self.scrollView.scrollRectToVisible(activeField.frame, animated: true)
       }
   }
}

func keyboardWillBeHidden(notification: NSNotification){
   var info = notification.userInfo!
   let keyboardSize = (info[UIKeyboardFrameBeginUserInfoKey] as? NSValue)?.cgRectValue.size
   let contentInsets : UIEdgeInsets = UIEdgeInsetsMake(0.0, 0.0, -keyboardSize!.height, 0.0)
   self.scrollView.contentInset = contentInsets
   self.scrollView.scrollIndicatorInsets = contentInsets
   self.view.endEditing(true)
   self.scrollView.isScrollEnabled = false
}

func textFieldDidBeginEditing(_ textField: UITextField){
   activeField = textField
}

func textFieldDidEndEditing(_ textField: UITextField){
   activeField = nil
}