设置 UITextField 的最大字符长度

Question

当我加载 UIView 时，如何在 iPhone SDK 上设置 UITextField 中的最大字符数？

Answer 1

如果您限制文本计数的目的是确保文本适合其他地方的 UILabel，我会避免使用字符计数。它会因一些表情符号而崩溃（尝试截断双倍大小的表情符号可能会使您的应用程序崩溃）。这也是一些语言（如日语和中文）的问题，它们有两步输入过程，简单的计数是行不通的。

我构建了一个 UITextField 插入子类 (MPC_CharacterLimitedTextField on github)。你给它提供预期的输出标签宽度，它会处理所有语言、表情符号和粘贴问题。无论字符数如何，它都只会收集适合标签的完整字符。该项目中有一个演示，因此您可以对其进行测试以查看它是否是您所需要的。希望它会帮助任何在输出长度方面遇到与我相同问题的人。

Answer 2

您也可以使用 Swift 4 中的 NotificationCenter 来完成此操作

NotificationCenter.default.addObserver(self, selector: #selector(self.handleTextChange(recognizer:)), name: NSNotification.Name.UITextFieldTextDidChange, object: yourTextField)

    @objc func handleTextChange(recognizer: NSNotification) {
            //max length is 50 charater max
            let textField = recognizer.object as! UITextField

            if((textField.text?.count)! > 50) {
                let newString: String? = (textField.text as NSString?)?.substring(to: 50)
                textField.text = newString

            }         
        }

Answer 3

Swift 4.2 和 UITextFieldDelegate 方法

这对我有用，并将文本字段的最大输入限制为 8 个字符。希望 NSRange 最终会更改为 Range，但现在我很高兴使用 NSString，因为从 NSRange 创建 Range 涉及到处理另一个可选项。

func textField(_ textField: UITextField, shouldChangeCharactersIn range: NSRange, replacementString string: String) -> Bool {
    let text = textField.text ?? ""
    let nsString = text as NSString
    let newText = nsString.replacingCharacters(in: range, with: string)
    return newText.count <= 8
}

Answer 4

上面给出的一些答案的问题是，例如我有一个文本字段，我必须设置输入 15 个字符的限制，然后在输入第 15 个字符后停止。但他们不允许删除。那就是删除按钮也不起作用。因为我面临同样的问题。提出了解决方案，如下所示。非常适合我

- (BOOL)textField:(UITextField *)textField shouldChangeCharactersInRange:(NSRange)range replacementString:(NSString *)string
{
 if(textField.tag==6)
 {
    if ([textField.text length]<=30)
    {
        return YES;   
    }
    else if([@"" isEqualToString:string])
    {
        textField.text=[textField.text substringToIndex:30 ];
    }

    return NO;
 }
 else
 {
    return YES;
 }
}

我有一个文本字段，我已将其标记设置为“6” 我已经限制了最大字符限制 = 30； 在任何情况下都可以正常工作

Answer 5

(BOOL)textField:(UITextField *)textField shouldChangeCharactersInRange:(NSRange)range replacementString:(NSString *)string
{
    NSString *newString = [textField.text stringByReplacingCharactersInRange:range withString:string];

    if ([txt_name.text length]>100)
    {
        return NO;
    }

    return YES;
}

Answer 6

这限制了字符数，但还要确保您可以在字段中粘贴直到最大限制。

- (void)textViewDidChange:(UITextView *)textView
{
    NSString* str = [textView text];
    str = [str substringToIndex:MIN(1000,[str length])];
    [textView setText:str];

    if([str length]==1000) {
        // show some label that you've reached the limit of 1000 characters
    }
}

Answer 7

除了回答原始问题并扩展 Frouo 的答案之外，这里有一些扩展来修剪空格字符串和最大长度，并利用这些字符串扩展来修剪 UITextField 到最大长度：

// In String_Extensions.swift

extension String {

  func trimmedString() -> String {
    var trimmedString = self.stringByTrimmingCharactersInSet(NSCharacterSet.whitespaceAndNewlineCharacterSet())
    let components = trimmedString.componentsSeparatedByCharactersInSet(NSCharacterSet.whitespaceAndNewlineCharacterSet()).filter { count($0) > 0 }
    return " ".join(components)
  }

  func trimmedStringToMaxLength(maxLength: Int) -> String {
    return trimmedString().substringToIndex(advance(startIndex, min(count(self), maxLength))).trimmedString()
  }

}

// In UITextField_Extensions.swift

private var maxLengthDictionary = [UITextField : Int]()
private var textFieldMaxLength = 20

extension UITextField {

  @IBInspectable var maxLength: Int {
    get {
      if let maxLength = maxLengthDictionary[self] {
        return maxLength
      } else {
        return textFieldMaxLength
      }
    }
    set {
      maxLengthDictionary[self] = newValue < textFieldMaxLength + 1 ? newValue : textFieldMaxLength
    }
  }

  func trimAndLimitToMaxLength() {
    text = text.trimmedStringToMaxLength(maxLength)
  }

}

let someTextField = UITextField()
let someString = "   This   is   a   string   that   is longer than allowable for a text field.   "
someTextField.text = someString
someTextField.trimAndLimitToMaxLength()
println(someTextField.text) // Prints "This is a string tha"
let anotherTextField = UITextField()
anotherTextField.maxLength = 5
anotherTextField.text = someString
anotherTextField.trimAndLimitToMaxLength()
println(anotherTextField.text) // Prints "This"

trimAndLimitToMaxLength() 可以在 UITextFieldDelegate 的textFieldDidEndEditing(_:) 中使用，以便用户可以输入或粘贴比可接受的更长的字符串，然后将其缩短而不是仅以最大长度切断输入。为此，我还将设置属性文本样式以指示超出可接受长度的任何文本部分（例如，[NSBackgroundColorAttributeName : UIColor.redColor(), NSForegroundColorAttributeName : UIColor.whiteColor(), NSStrikethroughStyleAttributeName : NSNumber(int: 1)]

Answer 8

我们可以像这样设置文本字段的范围..

-(BOOL)textField:(UITextField *)textField shouldChangeCharactersInRange:(NSRange)range  replacementString:(NSString *)string
{
     int setrange = 20;
     return !([textField.text length]>setrange && [string length] > range.length);
}

Answer 9

对于 Swift 2.1+

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

    if (range.length + range.location > textField.text!.characters.count )
    {
        return false;
    }

    let newLength = textField.text!.characters.count + string.characters.count - range.length
    return newLength <= 25
}

希望对你有帮助

Answer 10

我想补充@sickp 给出的答案。

他的Swift 代码中存在一个问题，该问题出现在任何多字节文本（例如表情符号）中。 NSRange 和 Swift 中的 String 不兼容，因此委托类将它们结合起来令人沮丧。诀窍是将String 对象转换为NSString 根据@sickp 所写的内容，正确的解决方案实际上是这样的：

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

    let currentText = (textField.text as NSString?) ?? NSString()
    let currentCharacterCount = currentText.length
    if range.length + range.location > currentCharacterCount {
        return false
    }
    let newLength = currentText.replacingCharacters(in: range, with: string).characters.count
    return newLength <= 25
}

Answer 11

适用于 Swift 3.1 或更高版本

首先添加协议UITextFieldDelegate

喜欢：-

class PinCodeViewController: UIViewController, UITextFieldDelegate { 
.....
.....
.....

}

之后创建你的 UITextField 并设置委托

完整的经验：-

import UIKit

class PinCodeViewController: UIViewController, UITextFieldDelegate {

let pinCodetextField: UITextField = {
    let tf = UITextField()
    tf.placeholder = "please enter your pincode"
    tf.font = UIFont.systemFont(ofSize: 15)
    tf.borderStyle = UITextBorderStyle.roundedRect
    tf.autocorrectionType = UITextAutocorrectionType.no
    tf.keyboardType = UIKeyboardType.numberPad
    tf.clearButtonMode = UITextFieldViewMode.whileEditing;
    tf.contentVerticalAlignment = UIControlContentVerticalAlignment.center
 return tf
  }()


 override func viewDidLoad() {
   super.viewDidLoad()
   view.addSubview(pinCodetextField)
    //----- setup your textfield anchor or position where you want to show it----- 


    // after that 
pinCodetextField.delegate = self // setting the delegate

 }
func textField(_ textField: UITextField, shouldChangeCharactersIn range: NSRange, replacementString string: String) -> Bool {
    return !(textField.text?.characters.count == 6 && string != "")
     } // this is return the maximum characters in textfield 
    }

Answer 12

在 Swift 5.2 中工作：

 class AngListVC: UIViewController, UITextFieldDelegate {

    @IBOutlet weak var angTextField: UITextField!

    override func viewDidLoad() {
        super.viewDidLoad()
        angTextField.delegate = self
        angTextField.addTarget(self, action: #selector(textFieldDidChange(_:)), for: .editingChanged)
      
    }

   func textField(_ textField: UITextField, shouldChangeCharactersIn range: NSRange, replacementString string: String) -> Bool {
           let userText =  angTextField.text ?? ""
           var newText = ""
           if range.length > 0 {
               let txt = NSString(string: userText)
               if txt.length > 0 {
                   newText = txt.replacingCharacters(in: range, with: "")
               }
           } else {
               newText = userText + ""
           }
           return newText.count <= 3
       }

@objc func textFieldDidChange(_ textField: UITextField) {
        print("textFieldDidChange")
   }

Answer 13

对于 Swift 5

添加这个 UITextfield 的扩展，然后选择一个文本域并检查属性检查器

private var __maxLengths = [UITextField: Int]()

extension UITextField {
    @IBInspectable var maxLength: Int {
        get {
            guard let l = __maxLengths[self] else {
               return 150 // (default int limit)
            }
            return l
        }
        set {
            __maxLengths[self] = newValue
            addTarget(self, action: #selector(setMaxLength), for: .editingChanged)
        }
    }

    @objc func setMaxLength(textField: UITextField) {
        let t = textField.text
        textField.text = t?.prefix(maxLength).description
    }
}

Answer 14

-(BOOL)textField:(UITextField *)textField shouldChangeCharactersInRange:(NSRange)range replacementString:(NSString *)string {
    if (textField.text.length >= 50) {
        return NO;
    }
    return YES;
}

Answer 15

Swift 4.2+

通过实现UITextFieldDelegate方法

1. 视图控制器：

   class MyViewController: UIViewController {
   
       let MAX_LENGTH = 256
   
       @IBOutlet weak var myTextField: UITextField!
   
       override viewDidLoad() {
           self.myTextField.delegate = self
       }
   }
   

2. 代表：

   extension MyViewController: UITextFieldDelegate {
   
       func textField(_ textField: UITextField, shouldChangeCharactersIn range: NSRange, replacementString string: String) -> Bool {
           let userText =  textView.text ?? ""
           var newText = ""
           if range.length > 0 {
               let txt = NSString(string: userText)
               if txt.length > 0 {
                   newText = txt.replacingCharacters(in: range, with: text)
               }
           } else {
               newText = userText + text
           }
           return newText.count <= MAX_LENGTH
       }
   
   }
   

Answer 16

我发现这个快速简单

- (IBAction)backgroundClick:(id)sender {
    if (mytext.length <= 7) {
        [mytext resignFirstResponder];
    } else {
        UIAlertView *alert = [[UIAlertView alloc] initWithTitle:@"Too Big" 
                                                        message:@"Please Shorten Name"
                                                       delegate:nil 
                                              cancelButtonTitle:@"Cancel"
                                              otherButtonTitles:nil];
        [alert show];
        [alert release];
    }
}