在更改事件上将货币格式重新应用于UITextField

Question

我正在使用一个包含本地化货币值的UITextField.我已经看过很多关于如何使用它的帖子,但我的问题是:如何在每次按键后将货币格式重新应用到UITextField？

我知道我可以设置和使用货币格式化程序:

NSNumberFormatter *currencyFormatter = [[NSNumberFormatter alloc] init];
[currencyFormatter setNumberStyle:NSNumberFormatterCurrencyStyle];
...
[currencyFormatter stringFromNumber:...];

但我不知道如何勾选它.

例如,如果字段中的值显示为"$ 12,345"并且用户点击"6"键,则该值应更改为"$ 123,456".

哪个回调是执行此操作的"正确"(我应该使用textField:shouldChangeCharactersInRange:replacementString:或自定义目标操作),如何使用NSNumberFormatter解析并重新应用格式到UITextField的文本属性？

任何帮助将非常感激!谢谢!

Answer 1

我一直在研究这个问题,我想我找到了一个很好的,干净的解决方案.我将向您展示如何正确更新用户输入的文本字段,但您必须自己弄清楚本地化,无论如何该部分应该很容易.

- (void)viewDidLoad
{
    [super viewDidLoad];


    // setup text field ...

#define PADDING 10.0f

    const CGRect bounds = self.view.bounds;
    CGFloat width       = bounds.size.width - (PADDING * 2);
    CGFloat height      = 30.0f;
    CGRect frame        = CGRectMake(PADDING, PADDING, width, height);

    self.textField                      = [[UITextField alloc] initWithFrame:frame];
    _textField.backgroundColor          = [UIColor whiteColor];
    _textField.contentVerticalAlignment = UIControlContentVerticalAlignmentCenter;
    _textField.autocapitalizationType   = UITextAutocapitalizationTypeNone;
    _textField.autocorrectionType       = UITextAutocorrectionTypeNo;
    _textField.text                     = @"0";
    _textField.delegate                 = self;
    [self.view addSubview:_textField];
}

- (void)viewDidAppear:(BOOL)animated
{
    [super viewDidAppear:animated];


    // force update for text field, so the initial '0' will be formatted as currency ...

    [self textField:_textField shouldChangeCharactersInRange:NSMakeRange(0, 0) replacementString:@"0"];
}

- (void)viewDidUnload
{
    self.textField = nil;

    [super viewDidUnload];
}

这是UITextFieldDelegate方法中的代码textField:shouldChangeCharactersInRange:replacementString:

- (BOOL)textField:(UITextField *)textField shouldChangeCharactersInRange:(NSRange)range replacementString:(NSString *)string
{
    NSString *text             = _textField.text;
    NSString *decimalSeperator = @".";
    NSCharacterSet *charSet    = nil;
    NSString *numberChars      = @"0123456789";


    // the number formatter will only be instantiated once ...

    static NSNumberFormatter *numberFormatter;
    if (!numberFormatter)
    {
        numberFormatter = [[NSNumberFormatter alloc] init];
        numberFormatter.numberStyle           = NSNumberFormatterCurrencyStyle;
        numberFormatter.maximumFractionDigits = 10;
        numberFormatter.minimumFractionDigits = 0;
        numberFormatter.decimalSeparator      = decimalSeperator;
        numberFormatter.usesGroupingSeparator = NO;
    }


    // create a character set of valid chars (numbers and optionally a decimal sign) ...

    NSRange decimalRange = [text rangeOfString:decimalSeperator];
    BOOL isDecimalNumber = (decimalRange.location != NSNotFound);
    if (isDecimalNumber)
    {
        charSet = [NSCharacterSet characterSetWithCharactersInString:numberChars];        
    }
    else
    {
        numberChars = [numberChars stringByAppendingString:decimalSeperator];
        charSet = [NSCharacterSet characterSetWithCharactersInString:numberChars];
    }


    // remove amy characters from the string that are not a number or decimal sign ...

    NSCharacterSet *invertedCharSet = [charSet invertedSet];
    NSString *trimmedString = [string stringByTrimmingCharactersInSet:invertedCharSet];
    text = [text stringByReplacingCharactersInRange:range withString:trimmedString];


    // whenever a decimalSeperator is entered, we'll just update the textField.
    // whenever other chars are entered, we'll calculate the new number and update the textField accordingly.

    if ([string isEqualToString:decimalSeperator] == YES) 
    {
        textField.text = text;
    }
    else 
    {
        NSNumber *number = [numberFormatter numberFromString:text];
        if (number == nil) 
        {
            number = [NSNumber numberWithInt:0];   
        }
        textField.text = isDecimalNumber ? text : [numberFormatter stringFromNumber:number];
    }

    return NO; // we return NO because we have manually edited the textField contents.
}

编辑1:修复内存泄漏.

编辑2:为Umka更新 - 处理0小数点后分隔符.代码也为ARC更新.