更改键盘通知上的视图布局(Swift，iOS)

Question

我正试图使用Swift为iOS应用程序创建一个登录屏幕。

这是我想要的没有隐藏键盘的样子。一旦用户点击一个文本字段，我想把它改成这样，并显示键盘。正如你所看到的，它是更紧凑的

我试着自己做，但似乎无法用我在网上找到的例子来解决，因为我在InterfaceBuilder中使用AutoLayoutConstraints。所有内容都嵌入到UIScrollView中。

我的问题是，我这样做正确吗？与中一样，删除之前在InterfaceBuilder中设置的所有约束，然后以编程方式重新进行它们，使其看起来像我想要的那样。

有更好的方法吗？这似乎很乏味。我是Swift/iOS编程的新手，所以如果这是一个明显的问题，我很抱歉。

以下是我迄今为止所做的：

---

@IBOutlet weak var scrollView: UIScrollView!
@IBOutlet weak var logoImage: UIImageView!
@IBOutlet weak var logoText: UILabel!
@IBOutlet weak var usernameTextField: UITextField!
@IBOutlet weak var passwordTextField: UITextField!
@IBOutlet weak var loginButton: UIButton!
@IBOutlet weak var forgotPasswordButton: UIButton!
@IBOutlet weak var createAccountButton: UIButton!
override func viewDidLoad() {
  super.viewDidLoad()
  registerForKeyboardNotifications()
}

---

func registerForKeyboardNotifications() {
        let notificationCenter = NSNotificationCenter.defaultCenter()
        notificationCenter.addObserver(self, selector: "keyboardWillBeShown:", name: UIKeyboardWillShowNotification, object: nil)
        notificationCenter.addObserver(self, selector: "keyboardWillBeHidden:", name: UIKeyboardWillHideNotification, object: nil)
}

---

func keyboardWillBeShown(sender: NSNotification) {
    let userInfo = sender.userInfo!
    let keyboardHeight = (userInfo[UIKeyboardFrameEndUserInfoKey] as! NSValue).CGRectValue().height
    let screenSize: CGRect = UIScreen.mainScreen().bounds           // get screen size
    let screenWidth = screenSize.width                              // ... screen width
    let screenHeight = screenSize.height                            // ... screen height
    let heightToFit = screenHeight - keyboardHeight                 // ... height of screen with keyboard
    self.view.translatesAutoresizingMaskIntoConstraints = false
    self.view.removeConstraints(self.view.constraints)
    self.view.addConstraint(
    NSLayoutConstraint(item: self.scrollView,
                  attribute: .Bottom,
                  relatedBy: .Equal,
                     toItem: self.view,
                  attribute: .Bottom,
                 multiplier: 1.0,
                   constant: -keyboardHeight ))
    self.view.addConstraint(
    NSLayoutConstraint(item: self.scrollView,
                  attribute: .Top,
                  relatedBy: .Equal,
                     toItem: self.view,
                  attribute: .Top,
                 multiplier: 1.0,
                   constant: 0.0))

    self.view.addConstraint(
    NSLayoutConstraint(item: self.scrollView,
                  attribute: .Trailing,
                  relatedBy: .Equal,
                     toItem: self.view,
                  attribute: .Trailing,
                 multiplier: 1.0,
                   constant: 0.0))
    self.view.addConstraint(
    NSLayoutConstraint(item: self.scrollView,
                  attribute: .Leading,
                  relatedBy: .Equal,
                     toItem: self.view,
                  attribute: .Leading,
                 multiplier: 1.0,
                   constant: 0.0))
    self.view.addConstraint(
    NSLayoutConstraint(item: self.scrollView,
                  attribute: .Height,
                  relatedBy: .Equal,
                     toItem: nil,
                  attribute: .NotAnAttribute,
                 multiplier: 1.0,
                   constant: heightToFit))
    self.view.addConstraint(
    NSLayoutConstraint(item: self.view,
                  attribute: .Width,
                  relatedBy: .Equal,
                     toItem: nil,
                  attribute: .NotAnAttribute,
                 multiplier: 1.0,
                   constant: screenWidth))

    self.scrollView.setContentOffset(CGPointMake(0, self.usernameTextField.frame.origin.y - 50), animated: true)
}

---

func keyboardWillBeHidden(sender: NSNotification) {
        let screenSize: CGRect = UIScreen.mainScreen().bounds           // get screen size
        let screenWidth = screenSize.width                              // ... screen width
        let screenHeight = screenSize.height                            // ... screen height
        self.view.translatesAutoresizingMaskIntoConstraints = true
        self.view.removeConstraints(self.view.constraints)
        self.view.addConstraint(
            NSLayoutConstraint(item: self.scrollView,
                          attribute: .Bottom,
                          relatedBy: .Equal,
                             toItem: self.view,
                          attribute: .Bottom,
                         multiplier: 1.0,
                           constant: screenHeight ))
        self.view.addConstraint(
            NSLayoutConstraint(item: self.scrollView,
                          attribute: .Top,
                          relatedBy: .Equal,
                             toItem: self.view,
                          attribute: .Top,
                        multiplier: 1.0,
                          constant: 0.0))
        self.view.addConstraint(
            NSLayoutConstraint(item: self.scrollView,
                          attribute: .Trailing,
                          relatedBy: .Equal,
                             toItem: self.view,
                          attribute: .Trailing,
                         multiplier: 1.0,
                           constant: 0.0))
        self.view.addConstraint(
            NSLayoutConstraint(item: self.scrollView,
                          attribute: .Leading,
                          relatedBy: .Equal,
                             toItem: self.view,
                          attribute: .Leading,
                         multiplier: 1.0,
                           constant: 0.0))
        self.view.addConstraint(
            NSLayoutConstraint(item: self.scrollView,
                          attribute: .Height,
                          relatedBy: .Equal,
                             toItem: nil,
                          attribute: .NotAnAttribute,
                        multiplier: 1.0,
                          constant: screenHeight))
        self.view.addConstraint(
            NSLayoutConstraint(item: self.view,
                          attribute: .Width,
                          relatedBy: .Equal,
                             toItem: nil,
                          attribute: .NotAnAttribute,
                         multiplier: 1.0,
                           constant: screenWidth))

  self.scrollView.setContentOffset(CGPointMake(0, -self.usernameTextField.frame.origin.y + 50), animated: true)
}

Answer 1

不幸的是，我无法让它与AutoLayoutConstraints一起工作，所以我禁用了它，并自己做了所有的数学运算。

这里有一个小片段：

let screenSize: CGRect = UIScreen.mainScreen().bounds           // get screen size
let screenWidth = screenSize.width                              // ... screen width
let screenHeight = screenSize.height                            // ... screen height
let padding: CGFloat = 30                                       // space on left and right
let adjustedViewWidth = screenWidth - 2*padding
self.scrollView.frame = CGRectMake(0, 0, screenWidth, screenHeight)
self.logoImage.frame = CGRectMake(screenWidth/2 - self.logoImage.frame.width/2, self.logoImage.frame.origin.y, self.logoImage.frame.width, self.logoImage.frame.height)
self.logoText.frame = CGRectMake(screenWidth/2 - self.logoText.frame.width/2, self.logoText.frame.origin.y, self.logoText.frame.width, self.logoText.frame.height)
self.usernameTextField.frame = CGRectMake(screenWidth/2 - adjustedViewWidth/2, self.usernameTextField.frame.origin.y, adjustedViewWidth, self.usernameTextField.frame.height)
self.passwordTextField.frame = CGRectMake(screenWidth/2 - adjustedViewWidth/2, self.passwordTextField.frame.origin.y, adjustedViewWidth, self.passwordTextField.frame.height)
self.loginButton.frame = CGRectMake(screenWidth/2 - adjustedViewWidth/2, self.loginButton.frame.origin.y, adjustedViewWidth, self.loginButton.frame.height)