UITextField 只接受一位小数点，小数点前最多 3 位，小数点后最多 2 位

Question

我想限制UITextField只接受一位小数。

小数点前最多允许 3 位数字，小数点后最多允许 2 位数字。

请注意，最小位数可以为 1，小数不能先输入。

如何实现？

Answer 1

您可以使用以下代码来实现相同的场景。

-(BOOL)textField:(UITextField *)textField shouldChangeCharactersInRange:(NSRange)range replacementString:(NSString *)string 
{
NSString *expression = @"^([0-9]*)(\.([0-9]+)?)?$";

    NSRegularExpression *regex = [NSRegularExpression regularExpressionWithPattern:expression options:NSRegularExpressionCaseInsensitive error:nil];
    NSUInteger noOfMatches = [regex numberOfMatchesInString:newStr options:0 range:NSMakeRange(0,[newStr length])];

    if (noOfMatches==0)
    {
        return NO;
    }

NSUInteger newLength = [textField.text length] + [string length] - range.length;
    if(range.length + range.location > textField.text.length)
    {
        return NO;
    }
    if ([newStr containsString:@"."])
    {
        return newLength <= 6;
    }
    return newLength <= 3;

    //  return YES;
}

因为.被认为是一个字符。所以总共是 6 个字符。您可以调整条件中的值。

Answer 2

这是使用 Swift 和 正则表达式:

实现的方法

设置文本字段的委托。这可以在代码或 IB 中完成。

要验证用户键入的文本，您可以将类似于以下内容的代码添加到您的委托中：

// Number of digits that are allowed before decimal point
let kMaximumIntegerDigits = 3
// Number of digits that are allowed after decimal point
let kMaximumFractionDigits = 2

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

// The replacement string is empty when the user have removed some characters.
if string.isEmpty == true { return true }

// Get the current string the text field holds.
let currentText = textField.text ?? ""

// Check the limits.
if (string.characters.count + currentText.characters.count) > 6 { return false }

// Get the string we are expecting to obtain after the replacement.
var resultingText = currentText
resultingText.insertContentsOf(string.characters, at: currentText.startIndex.advancedBy(range.location))

// Check the final string with the help of the regular expression.
let regex = "^(?:(?:[0-9]{1,\(kMaximumIntegerDigits)}[.][0-9]{0,\(kMaximumFractionDigits)})|(?:[0-9]){1,\(kMaximumIntegerDigits)})$"
let regexRange = resultingText.rangeOfString(regex, options: .RegularExpressionSearch)
if regexRange == nil { return false }

return true

}

最后，当用户试图结束编辑会话时，您应该验证生成的文本。你可以这样做：

func textFieldShouldEndEditing(textField: UITextField) -> Bool {
 // Get the current input string.
 guard let currentText = textField.text else { return false }

 // Create the regular expression for the final check.
 let regex = "^(?:(?:[0-9]{1,\(kMaximumIntegerDigits)}[.][0-9]{1,\(kMaximumFractionDigits)})|(?:[0-9]){1,\(kMaximumIntegerDigits)})$"
 let regexRange = currentText.rangeOfString(regex, options: .RegularExpressionSearch)
 if regexRange == nil { 
 // Show an alert to the user with the message that explains what the input is expected...
 return false 
 }

 // Make additional clean-up and finalize the editing session.
 return true
}

Answer 3

非常感谢大家的帮助。通过参考这些答案，我将答案框在下面。

编辑

虽然文本字段具有例如462. & 用户触摸退格键结果为 462，理想情况下应为 46

    - (BOOL)textField:(UITextField *)textField shouldChangeCharactersInRange:(NSRange)range replacementString:(NSString *)string
    {
        NSString *strTextField = [textField.text stringByReplacingCharactersInRange:range withString:string];
    // restrict textfield from entering ./0 at first place
    if (strTextField.length > 0) {
        NSString *theCharacterAtIndex0 = [NSString stringWithFormat:@"%c", [strTextField characterAtIndex:0]];
        if ([theCharacterAtIndex0 isEqualToString:@"."] || [theCharacterAtIndex0 isEqualToString:@"0"]) {
            return NO;
        }
    }
    //    NSLog(@"%@ , %@", textField.text, strTextField);

    // automatically add decimal point after 3 digits entered
    if (![textField.text containsString:@"."]) {
        if (strTextField.length == MAX_LENGTH_BeforeDecimal && ![strTextField containsString:@"."]) {
            strTextField = [strTextField stringByAppendingString:@"."];
            textField.text = strTextField;
            return NO;
        }
    }

    // when decimal is deleted
    if ([textField.text containsString:@"."]) {
        if (![strTextField containsString:@"."]) {
            int indeOfdecimal = (int)[textField.text rangeOfString:@"."].location;
            NSString *strBeforeDecimal = [textField.text substringToIndex:indeOfdecimal];
            textField.text = strBeforeDecimal;
        }
    }

    NSArray *separator = [strTextField componentsSeparatedByString:@"."];
    // to restrict textfield to single decimal
    if([separator count] > 2 ) {
        return NO;
    }
    if([separator count] >= 2) {
        // restrict the max digits before & after decimal points
        NSString *sepStr0 = [NSString stringWithFormat:@"%@",[separator objectAtIndex:0]];
        NSString *sepStr1 = [NSString stringWithFormat:@"%@",[separator objectAtIndex:1]];
        if ([sepStr0 length] > 3) {
            return NO;
        }
        if ([sepStr1 length] > 2) {
            return NO;
        }
    }
    return YES;
}

Answer 4

使用这个正则表达式代码：

- (BOOL)textField:(UITextField *)textField shouldChangeCharactersInRange:(NSRange)range replacementString:(NSString *)string {
   // Only allow one decimal point and 2 digits after it
   NSString *newString = [textField.text stringByReplacingCharactersInRange:range withString:string];
   NSString *expression = @"^[0-9]{0,3}$*((\.|,)[0-9]{0,2})?$";
   NSError *error = nil;
   NSRegularExpression *regex = [NSRegularExpression regularExpressionWithPattern:expression options:NSRegularExpressionCaseInsensitive error:&error];
   NSUInteger numberOfMatches = [regex numberOfMatchesInString:newString options:0 range:NSMakeRange(0, [newString length])];
   return numberOfMatches != 0;
   return YES;
 }

这里使用的正则表达式是"^[0-9]{0,3}$*((\.|,)[0-9]{0,2})?$".

这里数字3（第一个粗体）表示小数点前的字符，数字2（第二个粗体）表示小数点后的字符。

您可以使用这个正则表达式并根据您的要求创建规则。

UITextField 只接受一位小数点，小数点前最多 3 位，小数点后最多 2 位

UITextField accepting only one decimal point with max 3 digits before decimal point & max 2 digits after decimal point

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