子视图不遵循约束并且关闭键盘会在视图底部留下一个黑色空间答案

【问题标题】：Subviews does not follow constraints and dismissing keyboard leaves a black space at the bottom of the view子视图不遵循约束并且关闭键盘会在视图底部留下一个黑色空间
【发布时间】：2020-02-05 02:01:46
【问题描述】：

每当我的根视图控制器（导航控制器）推送到我的第二个 VC（我们称之为 VC2）时，所有 VC2 的子视图：按钮、标签和文本字段都会向下移动，即使我已经对其设置了约束。此外，每当我在编辑文本字段后关闭键盘时，视图都会返回到约束设置它的预期位置，并在视图底部留下一个黑色空间。这是我的 VC2 代码：

override func viewDidLoad() {
    super.viewDidLoad()
    view.layer.backgroundColor = UIColor(named: const.white)?.cgColor

    nameField.delegate = self
    emailField.delegate = self
    passField.delegate = self

    setUpTitles()
    setUpTextFields()
    setUpButton()

    addPaddingAndBorder(to: nameField)
    addPaddingAndBorder(to: emailField)
    addPaddingAndBorder(to: passField)


    NotificationCenter.default.addObserver(self, selector: #selector(keyboardWillChangeView(notification:)), name: UIResponder.keyboardWillShowNotification, object: nil)
    NotificationCenter.default.addObserver(self, selector: #selector(keyboardIsDone(notification:)), name: UIResponder.keyboardWillHideNotification, object: nil)
    NotificationCenter.default.addObserver(self, selector: #selector(keyboardWillChangeView(notification:)), name: UIResponder.keyboardWillChangeFrameNotification, object: nil)

    let tap = UITapGestureRecognizer(target: self, action: #selector(dismissKeyboard(_:)))
    self.view.addGestureRecognizer(tap)

}

deinit {
    NotificationCenter.default.removeObserver(self, name: UIResponder.keyboardWillShowNotification, object: nil)
    NotificationCenter.default.removeObserver(self, name: UIResponder.keyboardWillHideNotification, object: nil)
    NotificationCenter.default.removeObserver(self, name: UIResponder.keyboardWillChangeFrameNotification, object: nil)

}

@objc func keyboardWillChangeView(notification: Notification){
    view.frame.origin.y = -150 //This is temporary

}

@objc func keyboardIsDone(notification: Notification){
    view.frame.origin.y = 0

}

@objc func dismissKeyboard(_: UITapGestureRecognizer){ //Tapping outside the keyboard 
    nameField.resignFirstResponder()
    emailField.resignFirstResponder()
    passField.resignFirstResponder()

}

//Executed when hitting return key
func textFieldShouldReturn(_ textField: UITextField) -> Bool {
    nameField.resignFirstResponder()
    emailField.resignFirstResponder()
    passField.resignFirstResponder()

    view.frame.origin.y = 0

    return true

}

之前：

之后：

【问题讨论】：

（UI 以编程方式构建）
可以加截图吗？
@ParthTamane 它不会让我
Imgur 链接怎么样？
如果您添加了约束，请尝试此代码 -> self.view.layoutIfNeeded() 如果您设置了框架并觉得这是问题所在。尝试将框架代码放入此 -> DispatchQueue.main.asyncAfter(deadline: .now()+0.2) { }

标签： swift xcode uikit

【解决方案1】：

当您使用响应者时，您应该将您的第一个文本字段设置为第一响应者，如下所示：

override func viewDidAppear(_ animated: Bool) {
        super.viewDidAppear(true)
        firstTextField.becomeFirstResponder()
    }

This is my answer in different issue

【讨论】：