我正在尝试检查文本字段何时更改，也等同于用于textView的功能- textViewDidChange到目前为止，我已经做到了：

  func textFieldDidBeginEditing(textField: UITextField) {
        if self.status.text == "" && self.username.text == "" {
            self.topRightButton.enabled = false
        } else {   
            self.topRightButton.enabled = true
        }
    }

哪种方法有效，但是topRightButton只要在按下文本字段时就启用，我希望仅在实际键入文本时才启用它？

迅速

斯威夫特4.2

textfield.addTarget(self, action: #selector(ViewController.textFieldDidChange(_:)), for: .editingChanged)

和

@objc func textFieldDidChange(_ textField: UITextField) {

}

SWIFT 3和Swift 4.1

textField.addTarget(self, action: #selector(ViewController.textFieldDidChange(_:)), for: .editingChanged)

和

func textFieldDidChange(_ textField: UITextField) {

}

SWIFT 2.2

textField.addTarget(self, action: #selector(ViewController.textFieldDidChange(_:)), forControlEvents: UIControlEvents.EditingChanged)

和

func textFieldDidChange(textField: UITextField) {
    //your code
}

目标C

[textField addTarget:self action:@selector(textFieldDidChange:) forControlEvents:UIControlEventEditingChanged];

和textFieldDidChange方法是

-(void)textFieldDidChange :(UITextField *) textField{
    //your code
}

您可以在界面构建器中建立此连接。

1. 在情节提要中，单击屏幕顶部的助手编辑器（中间两个圆圈）。

2. Ctrl +单击界面构建器中的文本字段。

3. 从EditingChanged拖动到助手视图中的视图控制器类内部。

4. 命名您的函数（例如“ textDidChange”），然后单击“连接”。

斯威夫特5.0

textField.addTarget(self, action: #selector(ViewController.textFieldDidChange(_:)),
                          for: .editingChanged)

处理方法：

@objc func textFieldDidChange(_ textField: UITextField) {

}

迅捷4.0

textField.addTarget(self, action: #selector(ViewController.textFieldDidChange(_:)),
                          for: UIControlEvents.editingChanged)

处理方法：

@objc func textFieldDidChange(_ textField: UITextField) {

}

斯威夫特3.0

textField.addTarget(self, action: #selector(textFieldDidChange(textField:)), for: .editingChanged)

处理方法：

func textFieldDidChange(textField: UITextField) { 

}

到目前为止，我的处理方式： UITextFieldDelegate

func textField(textField: UITextField, shouldChangeCharactersInRange range: NSRange, replacementString string: String) -> Bool
{
    // text hasn't changed yet, you have to compute the text AFTER the edit yourself
    let updatedString = (textField.text as NSString?)?.stringByReplacingCharactersInRange(range, withString: string)

    // do whatever you need with this updated string (your code)


    // always return true so that changes propagate
    return true
}

Swift4版本

func textField(_ textField: UITextField, shouldChangeCharactersIn range: NSRange, replacementString string: String) -> Bool {
    let updatedString = (textField.text as NSString?)?.replacingCharacters(in: range, with: string)
    return true
}

迅捷3

 textField.addTarget(self, action: #selector(ViewController.textFieldDidChange(sender:)), for: UIControlEvents.editingChanged)

Swift 3.0.1+（其他一些Swift 3.0答案不是最新的）

textField.addTarget(self, action: #selector(ViewController.textFieldDidChange(_:)),
                          for: UIControlEvents.editingChanged)

func textFieldDidChange(_ textField: UITextField) {

}

如果要检查每个按键，textField（_：shouldChangeCharactersIn：replacementString :)在Xcode 8，Swift 3中对我有用。

func textField(_ textField: UITextField, shouldChangeCharactersIn range: NSRange, replacementString string: String) -> Bool {

    // Whatever code you want to run here.
    // Keep in mind that the textfield hasn't yet been updated,
    // so use 'string' instead of 'textField.text' if you want to
    // access the string the textfield will have after a user presses a key

    var statusText = self.status.text
    var usernameText = self.username.text

    switch textField{
    case self.status:
        statusText = string
    case self.username:
        usernameText = string
    default:
        break
    }

    if statusText == "" && usernameText == "" {
        self.topRightButton.enabled = false
    } else {   
        self.topRightButton.enabled = true
    }

    //Return false if you don't want the textfield to be updated
    return true
}

斯威夫特4

符合UITextFieldDelegate。

func textField(_ textField: UITextField, shouldChangeCharactersIn range: NSRange, replacementString string: String) -> Bool {
    // figure out what the new string will be after the pending edit
    let updatedString = (textField.text as NSString?)?.replacingCharacters(in: range, with: string)

    // Do whatever you want here


    // Return true so that the change happens
    return true
}

您可以从UITextFieldDelegate使用此委托方法。每次角色更改都会触发。

(Objective C) textField:shouldChangeCharactersInRange:replacementString:
(Swift) textField(_:shouldChangeCharactersInRange:replacementString:)

但是，此操作仅在更改之前进行（实际上，仅当您从此处返回true时才进行更改）。

也许使用RxSwift？

需要

pod 'RxSwift',    '~> 3.0'
pod 'RxCocoa',    '~> 3.0'

明显增加进口

import RxSwift
import RxCocoa

所以你有一个 textfield : UITextField

let observable: Observable<String?> = textField.rx.text.asObservable()
observable.subscribe(
            onNext: {(string: String?) in
                print(string!)
        })

U还有其他3种方法。

1. onError
2. onCompleted
3. onDisposed
4. onNext

斯威夫特4

textField.addTarget(self, action: #selector(textIsChanging), for: UIControlEvents.editingChanged)

@objc func textIsChanging(_ textField:UITextField) {

 print ("TextField is changing")

}

如果您要在用户完全输入后进行更改（一旦用户关闭键盘或按Enter键，它将被调用）。

textField.addTarget(self, action: #selector(textDidChange), for: UIControlEvents.editingDidEnd)

 @objc func textDidChange(_ textField:UITextField) {

       print ("TextField did changed") 
 }

txf_Subject.addTarget(self, action:#selector(didChangeFirstText), for: .editingChanged)

@objc func didChangeText(textField:UITextField) {
    let str = textField.text
    if(str?.contains(" "))!{
        let newstr = str?.replacingOccurrences(of: " ", with: "")
        textField.text = newstr
    }
}

@objc func didChangeFirstText(textField:UITextField) {
    if(textField.text == " "){
        textField.text = ""
    }
}

您应该按照以下步骤操作：

1. 对文本字段进行出口引用
2. 将UITextFieldDelegate分配给控制器类
3. 配置yourTextField.delegate
4. 实现您需要的任何功能

样例代码：

import UIKit

class ViewController: UIViewController, UITextFieldDelegate {

    @IBOutlet var yourTextFiled : UITextField!

    override func viewDidLoad() {
        super.viewDidLoad()

        yourTextFiled.delegate = self
    }


    func textFieldDidEndEditing(_ textField: UITextField) {
        // your code
    }

    func textFieldShouldReturn(_ textField: UITextField) -> Bool {
        // your code
    }

    .
    .
    .
}

这是您可以textField text change listener使用Swift 3添加的方式：

宣布您的课程为 UITextFieldDelegate

override func viewDidLoad() {
    super.viewDidLoad()

    textField.delegate = self

    textField.addTarget(self, action: #selector(UITextFieldDelegate.textFieldShouldEndEditing(_:)), for: UIControlEvents.editingChanged)
}

然后只需传统上添加一个textFieldShouldEndEditing函数：

func textFieldShouldEndEditing(_ textField: UITextField) -> Bool { // do stuff
        return true 
}

斯威夫特4.2

写在viewDidLoad

// to detect if TextField changed
TextField.addTarget(self, action: #selector(textFieldDidChange(_:)),
                                   for: UIControl.Event.editingChanged)

在viewDidLoad外面写这个

@objc func textFieldDidChange(_ textField: UITextField) {
    // do something
}

您可以通过UIControl.Event.editingDidBegin或您想要检测的事件来更改事件。

万一您对SwiftUI解决方案感兴趣，那么它对我有用：

 TextField("write your answer here...",
            text: Binding(
                     get: {
                        return self.query
                       },
                     set: { (newValue) in
                        self.fetch(query: newValue) // any action you need
                                return self.query = newValue
                      }
            )
  )

我不得不说这不是我的主意，我在以下博客中阅读了它：SwiftUI绑定：一个非常简单的技巧

如果无法将addTarget绑定到您的UITextField，我建议您按照上面的建议将其中之一绑定，并在shouldChangeCharactersIn方法的末尾插入要执行的代码。

nameTextField.addTarget(self, action: #selector(RegistrationViewController.textFieldDidChange(_:)), for: .editingChanged)

@objc func textFieldDidChange(_ textField: UITextField) {
    if phoneNumberTextField.text!.count == 17 && nameTextField.text!.count > 0 {
        continueButtonOutlet.backgroundColor = UIColor(.green)
    } else {
        continueButtonOutlet.backgroundColor = .systemGray
    }
}

并在调用中应将ChangeCharactersIn函数中。

func textField(_ textField: UITextField, shouldChangeCharactersIn range: NSRange, replacementString string: String) -> Bool {

    guard let text = textField.text else {
        return true
    }
    let lastText = (text as NSString).replacingCharacters(in: range, with: string) as String

    if phoneNumberTextField == textField {
        textField.text = lastText.format("+7(NNN)-NNN-NN-NN", oldString: text)
        textFieldDidChange(phoneNumberTextField)
        return false
    }
    return true
}

迅捷4

在viewDidLoad（）中：

    //ADD BUTTON TO DISMISS KEYBOARD

    // Init a keyboard toolbar 
    let toolbar = UIView(frame: CGRect(x: 0, y: view.frame.size.height+44, width: view.frame.size.width, height: 44))
    toolbar.backgroundColor = UIColor.clear

    // Add done button
    let doneButt = UIButton(frame: CGRect(x: toolbar.frame.size.width - 60, y: 0, width: 44, height: 44))
    doneButt.setTitle("Done", for: .normal)
    doneButt.setTitleColor(MAIN_COLOR, for: .normal)
    doneButt.titleLabel?.font = UIFont(name: "Titillium-Semibold", size: 13)
    doneButt.addTarget(self, action: #selector(dismissKeyboard), for: .touchUpInside)
    toolbar.addSubview(doneButt)

    USDTextField.inputAccessoryView = toolbar

添加此功能：

    @objc func dismissKeyboard() {
      //Causes the view (or one of its embedded text fields) to resign the first responder status.
      view.endEditing(true)
    }

创建新的自定义类MaterialTextfield.swift

class MaterialTextfield: UITextField,UITextFieldDelegate {

var bottomBorder = UIView()
var shouldShowEditing = false

override func awakeFromNib() {

    // Setup Bottom-Border

    self.delegate = self
    self.translatesAutoresizingMaskIntoConstraints = false

    bottomBorder = UIView.init(frame: CGRect(x: 0, y: 0, width: 0, height: 0))
    bottomBorder.backgroundColor = UIColor(rgb: 0xE2DCD1) // Set Border-Color
    bottomBorder.translatesAutoresizingMaskIntoConstraints = false

    addSubview(bottomBorder)

    bottomBorder.bottomAnchor.constraint(equalTo: bottomAnchor).isActive = true
    bottomBorder.leftAnchor.constraint(equalTo: leftAnchor).isActive = true
    bottomBorder.rightAnchor.constraint(equalTo: rightAnchor).isActive = true
    bottomBorder.heightAnchor.constraint(equalToConstant: 1).isActive = true // Set Border-Strength

}
@IBInspectable var hasError: Bool = false {
    didSet {
        if (hasError) {
            bottomBorder.backgroundColor = UIColor.red//error color
        } else {
            bottomBorder.backgroundColor = UIColor(rgb: 0xE2DCD1)//passive color
        }

    }
}
@IBInspectable var showEditing: Bool = false{
    didSet {
        if (showEditing) {
            bottomBorder.backgroundColor = UIColor(rgb: 0x56B5CA)//active color
        } else {
            bottomBorder.backgroundColor = UIColor(rgb: 0xE2DCD1)//passive color
        }

    }

}

func textFieldDidBeginEditing(_ textField: UITextField) {//listen to on edit event
    showEditing = !self.showEditing
}
func textFieldDidEndEditing(_ textField: UITextField) {//listen to on end edit event
    showEditing = !self.showEditing
}

func textFieldShouldReturn(_ textField: UITextField) -> Bool {//listen to return button event
    textField.resignFirstResponder() // return button will close keyboard
    return true
}

}