Swift：当键盘显示时向上滚动视图

Posted 2023-03-17

【中文标题】Swift：当键盘显示时向上滚动视图

【英文标题】：Swift : scroll the view up when keyboard shows

【发布时间】：2014-11-23 21:13:07

【问题描述】：

我有一个 scrollView，我想在显示键盘时向上滚动。

当键盘显示时我遇到了这个错误：

2014-09-29 14:48:50.738 swrd[1563:472888] -[swrd.EditPhotoViewController keyboardWasShown]：无法识别的选择器发送到实例 0x14ed36640

这是我的代码，有什么问题？：

   func registerForKeyboardNotifications ()-> Void   

    NSNotificationCenter.defaultCenter().addObserver(self, selector: "keyboardWasShown", name: UIKeyboardDidShowNotification, object: nil)

    NSNotificationCenter.defaultCenter().addObserver(self, selector: "keyboardWillBeHidden", name: UIKeyboardWillHideNotification, object: nil)




func deregisterFromKeyboardNotifications () -> Void 
    let center:  NSNotificationCenter = NSNotificationCenter.defaultCenter()
    center.removeObserver(self, name: UIKeyboardDidHideNotification, object: nil)
    center.removeObserver(self, name: UIKeyboardWillHideNotification, object: nil)





 func keyboardWasShown (notification: NSNotification) 

    let info : NSDictionary = notification.userInfo!
    let keyboardSize = info.objectForKey(UIKeyboardFrameBeginUserInfoKey)?.frame

    let insets: UIEdgeInsets = UIEdgeInsetsMake(self.scrollView.contentInset.top, 0, keyboardSize!.height, 0)

    self.scrollView.contentInset = insets
    self.scrollView.scrollIndicatorInsets = insets

    self.scrollView.contentOffset = CGPointMake(self.scrollView.contentOffset.x, self.scrollView.contentOffset.y + keyboardSize!.height)



func keyboardWillBeHidden (notification: NSNotification) 

    let info : NSDictionary = notification.userInfo!
    let keyboardSize = info.objectForKey(UIKeyboardFrameBeginUserInfoKey)?.frame

    let insets: UIEdgeInsets = UIEdgeInsetsMake(self.scrollView.contentInset.top, 0, keyboardSize!.height, 0)

    self.scrollView.contentInset = insets
    self.scrollView.scrollIndicatorInsets = insets






 override func viewWillAppear(animated: Bool) 
    super.viewWillAppear(true)



   self.registerForKeyboardNotifications()



 override func viewWillDisappear(animated: Bool) 
    super.viewWillDisappear(true)

    self.deregisterFromKeyboardNotifications()

【参考方案1】：

在您的代码中，keyboardWasShown 和 keyboardWasHidden 各有一个参数，NSNotification。您需要用冒号终止 addObserver 中的选择器，以便它通过。即，keyboardWasShown 和 keyboardWasShown: 是不同的选择器。

NSNotificationCenter.defaultCenter().addObserver(self, selector: "keyboardWasShown:", name: UIKeyboardDidShowNotification, object: nil)

【参考方案2】：

请参阅下面的独立解决方案：

private func startObservingKeyboardEvents() 
  NSNotificationCenter.defaultCenter().addObserver(self,
    selector:Selector("keyboardWillShow:"),
    name:UIKeyboardWillShowNotification,
    object:nil)
  NSNotificationCenter.defaultCenter().addObserver(self,
    selector:Selector("keyboardWillHide:"),
    name:UIKeyboardWillHideNotification,
    object:nil)


private func stopObservingKeyboardEvents() 
  NSNotificationCenter.defaultCenter().removeObserver(self, name: UIKeyboardWillShowNotification, object: nil)
  NSNotificationCenter.defaultCenter().removeObserver(self, name: UIKeyboardWillHideNotification, object: nil)


func keyboardWillShow(notification: NSNotification) 
  if let userInfo = notification.userInfo 
    if let keyboardSize: CGSize = userInfo[UIKeyboardFrameEndUserInfoKey]?.CGRectValue().size 
      let contentInset = UIEdgeInsetsMake(0.0, 0.0, keyboardSize.height, 0.0);
    
  


func keyboardWillHide(notification: NSNotification) 
  let contentInset = UIEdgeInsetsZero;

使用contentInset 变量调整内容插入。

【讨论】：

感谢您提供所有代码，很棒的东西，谢谢！

【参考方案3】：

就我而言，需要对上面的代码进行一些更改：

1 - 首先，您需要在视图中放置一个 Scrollview，并设置如下约束：

滚动视图比视图更重要。

2 - 放置您需要的 TextField 和其他组件。

3 - 使用 @IBOutlet 将 ScrollView 链接到 ViewController

4 - 将委托添加到 ScrollView：

class ViewController: UIViewController, UITextFieldDelegate,     UIScrollViewDelegate 
...

5 - 添加观察者：

override func viewWillAppear(animated: Bool) 
   self.startKeyboardObserver()


override func viewWillDisappear(animated: Bool) 
   self.stopKeyboardObserver()



private func startKeyboardObserver()
  NSNotificationCenter.defaultCenter().addObserver(self, selector: "keyboardWillShow:", name: UIKeyboardWillShowNotification, object: nil) //WillShow and not Did ;) The View will run animated and smooth
  NSNotificationCenter.defaultCenter().addObserver(self, selector: "keyboardWillHide:", name: UIKeyboardWillHideNotification, object: nil)


private func stopKeyboardObserver() 
  NSNotificationCenter.defaultCenter().removeObserver(self, name: UIKeyboardWillShowNotification, object: nil)
  NSNotificationCenter.defaultCenter().removeObserver(self, name: UIKeyboardWillHideNotification, object: nil)

6 - 添加滚动代码，计算 KeyboardSize。

func keyboardWillShow(notification: NSNotification) 
      if let userInfo = notification.userInfo 
         if let keyboardSize: CGSize =    userInfo[UIKeyboardFrameEndUserInfoKey]?.CGRectValue().size 
            let contentInset = UIEdgeInsetsMake(0.0, 0.0, keyboardSize.height,  0.0);

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

        self.scrollView.contentOffset = CGPointMake(self.scrollView.contentOffset.x, 0 + keyboardSize.height) //set zero instead self.scrollView.contentOffset.y

       
    
 

func keyboardWillHide(notification: NSNotification) 
    if let userInfo = notification.userInfo 
       if let keyboardSize: CGSize =  userInfo[UIKeyboardFrameEndUserInfoKey]?.CGRectValue().size 
          let contentInset = UIEdgeInsetsZero;

        self.scrollView.contentInset = contentInset
        self.scrollView.scrollIndicatorInsets = contentInset
        self.scrollView.contentOffset = CGPointMake(self.scrollView.contentOffset.x, self.scrollView.contentOffset.y)
       
    
 

【讨论】：

键盘出现时有闪烁效果。第一个视图向上移动，然后它会来到点击字段