Swift：当键盘显示时向上滚动视图

Question

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()

}

Answer 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)

Answer 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。

Answer 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)
       }
    }
 }