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
使用下面的扩展来设置UITextField和UITextView的最大字符长度。
斯威夫特4.0
private var kAssociationKeyMaxLength: Int = 0
private var kAssociationKeyMaxLengthTextView: 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
}
}
UITextView
extension UITextView:UITextViewDelegate {
@IBInspectable var maxLength: Int {
get {
if let length = objc_getAssociatedObject(self, &kAssociationKeyMaxLengthTextView) as? Int {
return length
} else {
return Int.max
}
}
set {
self.delegate = self
objc_setAssociatedObject(self, &kAssociationKeyMaxLengthTextView, newValue, .OBJC_ASSOCIATION_RETAIN)
}
}
public func textViewDidChange(_ textView: UITextView) {
checkMaxLength(textField: self)
}
@objc func checkMaxLength(textField: UITextView) {
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
}
}
你可以在下面设置限制。
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);
}
Swift 4 + 2。
通过实现UITextFieldDelegate方法
ViewController: class MyViewController: UIViewController { let MAX_LENGTH = 256 @IBOutlet weak var myTextField: UITextField! override viewDidLoad() { self.myTextField.delegate = self } } Delegate: 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 } }
(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;
}
使用接口构建器,您可以在任何函数中链接并获得“编辑更改”的事件。 现在你可以检查长度
- (IBAction)onValueChange:(id)sender
{
NSString *text = nil;
int MAX_LENGTH = 20;
switch ([sender tag] )
{
case 1:
{
text = myEditField.text;
if (MAX_LENGTH < [text length]) {
myEditField.text = [text substringToIndex:MAX_LENGTH];
}
}
break;
default:
break;
}
}
现在你想要多少字符,只要给值就行了
- (BOOL)textField:(UITextField *)textField shouldChangeCharactersInRange:(NSRange)range replacementString:(NSString *)string {
NSUInteger newLength = [textField.text length] + [string length] - range.length;
return (newLength > 25) ? NO : YES;
}
推荐文章
- 如何删除默认的导航栏空间在SwiftUI导航视图
- 如何在iOS中使用Swift编程segue
- Swift -整数转换为小时/分钟/秒
- Swift:声明一个空字典
- 为什么ARC仍然需要@autoreleasepool ?
- 在成功提交我的应用程序后,“太多符号文件”
- 首先添加一个UIView,甚至是导航栏
- 我如何改变UIButton标题颜色?
- 如何从UIImage (Cocoa Touch)或CGImage (Core Graphics)获取像素数据?
- 在Swift中如何调用GCD主线程上的参数方法?
- NSLayoutConstraints是可动画的吗?
- iOS -构建失败,CocoaPods无法找到头文件
- Xcode 4挂在“附加到(应用程序名称)”
- CFNetwork SSLHandshake iOS 9失败
- 请求失败:不可接受的内容类型:文本/html使用AFNetworking 2.0