如何使用 NSNumberFormatter 格式化 UITextField？

Question

希望这对其他人有所帮助，因为我还没有在网上看到任何类似的帖子显示如何使用 NSNumberFormatter 格式化文本字段，但同时将 UITextField 光标位置保持在它应该自然的位置.那些，因为在格式化之后，UITextField 内部的NSString 并将其设置回field 最终会将光标放在field 的末尾。 对于需要它的人来说，将它转换为 Swift 也会很好。

Answer 1

这是我对这个问题的回答，我使用的是 UIKeyboardTypeNumberPad，但它也适用于 UIKeyboardTypeDecimalPad，如果使用其他键盘类型，请在使用下一个代码之前随意添加正则表达式：

- (int)getCharOccurencies:(NSString *)character inString:(NSString *)string{

    NSMutableArray *characters = [[NSMutableArray alloc] initWithCapacity:[string length]];
    for (int i=0; i < [string length]; i++) {
        NSString *ichar  = [NSString stringWithFormat:@"%c", [string characterAtIndex:i]];
        [characters addObject:ichar];
    }

    int count = 0;
    for (NSString *ichar in characters) {
        if ([ichar isEqualToString:character]) {
            count++;
        }
    }
    return count;

}

- (void)selectTextForInput:(UITextField *)input atRange:(NSRange)range {
    UITextPosition *start = [input positionFromPosition:[input beginningOfDocument]
                                                 offset:range.location];
    UITextPosition *end = [input positionFromPosition:start
                                               offset:range.length];
    [input setSelectedTextRange:[input textRangeFromPosition:start toPosition:end]];
}

- (BOOL)textField:(UITextField *)textField shouldChangeCharactersInRange:(NSRange)range replacementString:(NSString *)string{

    NSString *charUsedToFormat = @",";

    NSMutableString *textString = [NSMutableString stringWithString:[textField text]];
    [textField setTintColor:[UIColor darkGrayColor]];

    if ([string isEqualToString:charUsedToFormat]) {
        return NO;
    }

    if (range.location == 0 && [string isEqualToString:@"0"]) {
        return NO;
    }

    if ([[textString stringByReplacingCharactersInRange:range withString:string] length] == 0) {
        textField.text = @"";
        [self selectTextForInput:textField atRange:NSMakeRange(0, 0)];
        return NO;
    }

    NSString *replacebleString = [textString substringWithRange:range];

    if (string.length == 0 && [replacebleString isEqualToString:charUsedToFormat]) {

        NSRange newRange = NSMakeRange( range.location - 1, range.length);
        range = newRange;
        textString = [NSMutableString stringWithString:[textString stringByReplacingCharactersInRange:newRange withString:string]];
    }else{
         textString = [NSMutableString stringWithString:[textString stringByReplacingCharactersInRange:range withString:string]];
    }


    int commmaCountBefore = [self getCharOccurencies:charUsedToFormat inString:textString];

    textString = [NSMutableString stringWithString:[textString stringByReplacingOccurrencesOfString:charUsedToFormat withString:@""]];
    NSNumber *firstNumber = [NSNumber numberWithDouble:[textString doubleValue]];
    NSNumberFormatter *formatter = [[NSNumberFormatter alloc] init];
    [formatter setNumberStyle:NSNumberFormatterDecimalStyle];
    //just in case
    [formatter setFormatterBehavior:NSNumberFormatterBehavior10_4];
    [formatter setGroupingSeparator:charUsedToFormat];
    [formatter setDecimalSeparator:@""];
    [formatter setMaximumFractionDigits:0];
    textString = [NSMutableString stringWithString:[formatter stringForObjectValue:firstNumber]];
    textField.text = textString;

    int commmaCountAfter = [self getCharOccurencies:charUsedToFormat inString:textString];
    int commaDif = commmaCountAfter - commmaCountBefore;


    int cursorPossition = (int)range.location + (int)string.length + commaDif;

    //set cursor position
    NSLog(@"cursorPossition: %d", cursorPossition);


    [self selectTextForInput:textField atRange:NSMakeRange(cursorPossition, 0)];

    return NO;

}