iOS

Question

通知发生了奇怪的行为。每当我将一个 UITextfield 切换到另一个时，我的通知都会正常触发。但最近我注意到，当从一个 UITextField 切换到另一个时，它们现在并没有被触发，而是在隐藏键盘时正确触发。 Apple 改变了这个逻辑吗？

我需要将字段滚动到可见，并且由于 观察者 在切换时现在没有开火，字段不会变成可见的矩形。

我已经通过在 textFieldDidBeginEditing 上发布通知创建了一个替代方案，但如果可能的话，我希望返回原路。

Answer 1

我找到了问题的真正原因。如果 UITextfield 没有附件视图，则切换时不会调用键盘通知，如果有附件视图，则每次都会调用它们 (Why is UIKeyboardWillShowNotification called every time another TextField is selected?)

在我的例子中，我在每个字段上都有附件视图，但是在添加附件视图时，我向所有字段添加了相同的视图，这才是真正的问题。我需要将单独的 UIView 实例分配给不同的字段。一旦我这样做了，我的问题就消失了。

Answer 2

我遇到了完全相同的问题，我通过创建一个带有新按钮的 accessoryView 来处理它，该按钮是我实际按钮的副本。所以基本上，假设你有一个 UIButton，它粘在 UIViewController 的底部，你有 2 个 UITextField，当交替切换时，感觉不到 UIButton 曾经移动到别处但仍停留在键盘上。下面这段代码解释了如何解决这个问题：

@IBOutlet weak var signInBtn: UIButton!
@IBOutlet weak var passwordTextField: UITextField!
@IBOutlet weak var emailTextField: UITextField!

var accessoryViewKeyboard:UIView?
var btnAccessory:UIButton?


override func viewDidLoad() {
    super.viewDidLoad()

    passwordTextField.delegate = self
    emailTextField.delegate = self

    accessoryViewKeyboard = UIView(frame: signInBtn.frame)

    //Inputting the "accessoryViewKeyboard" here as the "inputAccessoryView" is of 
    //utmost importance to help the "signInBtn" to show up on tap of different "UITextFields"
    emailTextField.inputAccessoryView = accessoryViewKeyboard
    passwordTextField.inputAccessoryView = accessoryViewKeyboard

    setupBtnWithKeyboard()
}

func setupBtnWithKeyboard() {
    btnAccessory = UIButton(frame: CGRect(x: signInBtn.frame.origin.x, y: signInBtn.frame.origin.y, width: self.view.frame.size.width, height: signInBtn.frame.size.height))
    accessoryViewKeyboard?.addSubview(btnAccessory!)
    btnAccessory?.translatesAutoresizingMaskIntoConstraints = false
    btnAccessory?.frame = CGRect(x: (accessoryViewKeyboard?.frame.origin.x)!,
                                 y: (accessoryViewKeyboard?.frame.origin.y)!,
                                 width: self.view.frame.size.width,
                                 height: (accessoryViewKeyboard?.frame.size.height)!)

    btnAccessory?.backgroundColor = UIColor(red: 31/255, green: 33/255, blue: 108/255, alpha: 1)
    btnAccessory?.setTitle("Sign In", for: .normal)
    btnAccessory?.titleLabel?.font = .systemFont(ofSize: 22)
    btnAccessory?.titleLabel?.textColor = UIColor.white
    btnAccessory?.titleLabel?.textAlignment = .center
    btnAccessory?.isEnabled = true
    btnAccessory?.addTarget(self, action: #selector(SignIn.signInBtnPressed), for: .touchUpInside)

    NSLayoutConstraint.activate([
        btnAccessory!.leadingAnchor.constraint(equalTo:
            accessoryViewKeyboard!.leadingAnchor, constant: 0),
        btnAccessory!.centerYAnchor.constraint(equalTo:
            accessoryViewKeyboard!.centerYAnchor),
        btnAccessory!.trailingAnchor.constraint(equalTo:
            accessoryViewKeyboard!.trailingAnchor, constant: 0),
        btnAccessory!.heightAnchor.constraint(equalToConstant: signInBtn.frame.size.height),
        ])
}

大功告成。这将使 UIButton 始终出现在键盘上。重要的是无论你引入多少个 UITextField 实例，总是输入 accessoryViewKeyboard 作为它的 inputAccessoryView.

iOS - 切换 UITextfields 时不触发键盘通知

iOS - Keyboard Notifications not firing while switching UITextfields

nsnotifications

xcode10

ios12

swift4.2