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
通常您有多个长度不同的输入字段。
- (BOOL)textField:(UITextField *)textField shouldChangeCharactersInRange:(NSRange)range replacementString:(NSString *)string {
int allowedLength;
switch(textField.tag) {
case 1:
allowedLength = MAXLENGTHNAME; // triggered for input fields with tag = 1
break;
case 2:
allowedLength = MAXLENGTHADDRESS; // triggered for input fields with tag = 2
break;
default:
allowedLength = MAXLENGTHDEFAULT; // length default when no tag (=0) value =255
break;
}
if (textField.text.length >= allowedLength && range.length == 0) {
return NO; // Change not allowed
} else {
return YES; // Change allowed
}
}
其他回答
我已经实现了一个UITextField扩展,以添加一个maxLength属性。
它基于Xcode 6 IBInspectables,所以你可以在接口构建器上设置maxLength限制。
实现如下:
UITextField + MaxLength。h
#import <UIKit/UIKit.h>
@interface UITextField_MaxLength : UITextField<UITextFieldDelegate>
@property (nonatomic)IBInspectable int textMaxLength;
@end
UITextField + MaxLength。m
#import "UITextField+MaxLength.h"
@interface UITextField_MaxLength()
@property (nonatomic, assign) id <UITextFieldDelegate> superDelegate;
@end
@implementation UITextField_MaxLength
- (BOOL)textField:(UITextField *) textField shouldChangeCharactersInRange:(NSRange)range replacementString:(NSString *)string {
//validate the length, only if it's set to a non zero value
if (self.textMaxLength>0) {
if(range.length + range.location > textField.text.length)
return NO;
if (textField.text.length+string.length - range.length>self.textMaxLength) {
return NO;
}
}
//if length validation was passed, query the super class to see if the delegate method is implemented there
if (self.superDelegate && [self.superDelegate respondsToSelector:@selector(textField:shouldChangeCharactersInRange:replacementString:)]) {
return [self.superDelegate textField:textField shouldChangeCharactersInRange:range replacementString:string];
}
else{
//if the super class does not implement the delegate method, simply return YES as the length validation was passed
return YES;
}
}
- (void)setDelegate:(id<UITextFieldDelegate>)delegate {
if (delegate == self)
return;
self.superDelegate = delegate;
[super setDelegate:self];
}
//forward all non overriden delegate methods
- (id)forwardingTargetForSelector:(SEL)aSelector {
if ([self.superDelegate respondsToSelector:aSelector])
return self.superDelegate;
return [super forwardingTargetForSelector:aSelector];
}
- (BOOL)respondsToSelector:(SEL)aSelector {
if ([self.superDelegate respondsToSelector:aSelector])
return YES;
return [super respondsToSelector:aSelector];
}
@end
适用于Swift 3.1或更高版本
首先添加协议UITextFieldDelegate
如:-
class PinCodeViewController: UIViewController, UITextFieldDelegate {
.....
.....
.....
}
之后创建你的UITextField并设置委托
完成经验:-
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
}
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;
}
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;
}
}
Swift 5
添加UITextfield的扩展,然后选择一个文本字段并检查属性检查器
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
}
}
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