当我加载一个UIView时,我如何在iPhone SDK上设置UITextField的最大字符数?
当前回答
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")
}
其他回答
为了完成八月的回答,建议函数的一个可能实现(参见UITextField的委托)。
我没有测试domness代码,但我的代码不会卡住,如果用户达到了限制,它与一个新的字符串兼容,取代一个更小或等于一个。
-(BOOL)textField:(UITextField *)textField shouldChangeCharactersInRange:(NSRange)range replacementString:(NSString *)string {
//limit the size :
int limit = 20;
return !([textField.text length]>limit && [string length] > range.length);
}
稍微超出了回答原来的问题,并扩展了Frouo的答案,这里有扩展来修剪空白字符串和最大长度,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() could be used in UITextFieldDelegate's textFieldDidEndEditing(_:) so that a user could enter or paste in a longer than acceptable string and then shorten it vs. just cutting off the input at the max length. In doing this, I would also set attributed text styles to indicate any portion of the text that goes beyond the acceptable length (e.g., [NSBackgroundColorAttributeName : UIColor.redColor(), NSForegroundColorAttributeName : UIColor.whiteColor(), NSStrikethroughStyleAttributeName : NSNumber(int: 1)]
Swift 4.2和UITextFieldDelegate方法
这适用于我和限制文本字段有一个最大输入8个字符。希望NSRange最终会改变为Range,但现在我很高兴使用NSString从NSRange创建一个范围涉及到处理另一个可选。
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
}
其他答案不处理用户可以从剪贴板粘贴长字符串的情况。如果我粘贴一个很长的字符串,它应该被截断,但显示出来。 在你的委托中使用这个:
static const NSUInteger maxNoOfCharacters = 5;
-(IBAction)textdidChange:(UITextField * )textField
{
NSString * text = textField.text;
if(text.length > maxNoOfCharacters)
{
text = [text substringWithRange:NSMakeRange(0, maxNoOfCharacters)];
textField.text = text;
}
// use 'text'
}
斯威夫特4
import UIKit
private var kAssociationKeyMaxLength: Int = 0
extension UITextField {
@IBInspectable var maxLength: Int {
get {
if let length = objc_getAssociatedObject(self, &kAssociationKeyMaxLength) as? Int {
return length
} else {
return Int.max
}
}
set {
objc_setAssociatedObject(self, &kAssociationKeyMaxLength, newValue, .OBJC_ASSOCIATION_RETAIN)
addTarget(self, action: #selector(checkMaxLength), for: .editingChanged)
}
}
@objc func checkMaxLength(textField: UITextField) {
guard let prospectiveText = self.text,
prospectiveText.count > maxLength
else {
return
}
let selection = selectedTextRange
let indexEndOfText = prospectiveText.index(prospectiveText.startIndex, offsetBy: maxLength)
let substring = prospectiveText[..<indexEndOfText]
text = String(substring)
selectedTextRange = selection
}
}
编辑:内存泄漏问题修复。
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