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
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
}
希望能有所帮助
其他回答
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,然后它在输入第15个字符后停止。但是他们不允许删除。那就是删除按钮也不管用了。我也面临着同样的问题。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;
}
}
我有一个文本框,我将其标签设置为“6” 并且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
把它压缩到一行代码:)
将文本视图的委托设置为“self”,然后在你的.h中添加<UITextViewDelegate>,在你的.m中添加以下代码....你可以调整数字“7”为任何你想要的最大字符数。
-(BOOL)textView:(UITextView *)a shouldChangeTextInRange:(NSRange)b replacementText:(NSString *)c {
return ((a.text.length+c.length<=7)+(c.length<1)+(b.length>=c.length)>0);
}
这段代码负责输入新字符、删除字符、选择字符然后输入或删除、选择字符并剪切、粘贴,以及选择字符并粘贴。
完成了!
另外,用位操作编写这段代码的另一种很酷的方法是
-(BOOL)textView:(UITextView *)a shouldChangeTextInRange:(NSRange)b replacementText:(NSString *)c {
return 0^((a.text.length+c.length<=7)+(c.length<1)+(b.length>=c.length));
}
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。
斯威夫特3.0
当您粘贴字符串超过您的字符限制时,此代码工作正常。
func textView(_ textView: UITextView, shouldChangeTextIn range: NSRange, replacementText text: String) -> Bool {
let str = (textView.text + text)
if str.characters.count <= 10 {
return true
}
textView.text = str.substring(to: str.index(str.startIndex, offsetBy: 10))
return false
}
谢谢你的投票。:)
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
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