在UITextfield中使用NSNumberFormatter进行实时格式化

Question

我有UITextfield,用户可以输入一个美元金额,我希望textfield总是用两位小数格式化($.##).必须始终保持格式化.但我仍然坚持如何将输入的数字附加到文本字段中的现有数字？

//This delegate is called everytime a character is inserted in an UITextfield.
- (BOOL) textField:(UITextField *)textField shouldChangeCharactersInRange:(NSRange)range replacementString:(NSString *)string
{
    if ([textField tag] == amountTag)
    {

        NSString *amount = string;

//How do I append the already entered numbers in the textfield to the new entered values   ?
//??

        //Get new formatted value
        NSString *newAmount = [self formatCurrencyValue:[amount doubleValue]];

        [textField setText:[NSString stringWithFormat:@"%@",newAmount]];

        return NO;
    }

    //Returning yes allows the entered chars to be processed
    return YES;
}


-(NSString*) formatCurrencyValue:(double)value
{
    NSNumberFormatter *numberFormatter = [[[NSNumberFormatter alloc] init]autorelease];
    [numberFormatter setFormatterBehavior:NSNumberFormatterBehavior10_4];
    [numberFormatter setCurrencySymbol:@"$"];
    [numberFormatter setNumberStyle:NSNumberFormatterCurrencyStyle];

    NSNumber *c = [NSNumber numberWithFloat:value];
    return [numberFormatter stringFromNumber:c];
}

Answer 1

这是这个想法...

存储字符串值，附加到它，然后使用它进行操作。

在.h文件中定义一个NSMutableString

NSMutableString *storedValue;
@property (nonatomic, retain) NSMutableString *storedValue;

合成它。

然后这样做...

- (BOOL) textField:(UITextField *)textField shouldChangeCharactersInRange:(NSRange)range replacementString:(NSString *)string
{
   if ([textField tag] == amountTag)
    {
    [storedValue appendString:string];
    NSString *newAmount = [self formatCurrencyValue:([storedValue doubleValue]/100)];

    [textField setText:[NSString stringWithFormat:@"%@",newAmount]];
    return NO;
    }

    //Returning yes allows the entered chars to be processed
    return YES;
}