Swift中文本字段的百分比掩码

Question

我一直在尝试为值为0.00％的文本字段实现百分比掩码。如果用户点击“1”，它将变为0.01％。如果然后点击0则变为0.10％，依此类推。

我已经用货币实现了这个目标。而且我已经非常接近使用百分比，但没有设法创造我正在追求的。

因此，字段最初设置为0.00％。我想显示百分比符号，我希望最大数字为100.00％，我希望最大小数位数为2，就像用户输入时要更新的字段一样，我想要他们能够按退格键删除输入的最后一个号码。哦，当它达到最大值100.00时，按另一个数字不会重置值，或做任何搞砸的事情。

这是我试过的代码。我也尝试了很多变化：

func textFieldDidChanged(textField: UITextField) {
    numberFormatter.numberStyle = .PercentStyle
    numberFormatter.maximumFractionDigits = 2
    numberFormatter.minimumFractionDigits = 2
    numberFormatter.maximum = 100
    let text = textField.text!.stringByReplacingOccurrencesOfString(numberFormatter.percentSymbol, withString: "").stringByReplacingOccurrencesOfString(numberFormatter.groupingSeparator, withString: "").stringByReplacingOccurrencesOfString(numberFormatter.decimalSeparator, withString: "")
    textField.text = numberFormatter.stringFromNumber((text as NSString).doubleValue / 100.0)
}

我看了一遍，花了太长时间。请帮忙。

Answer 1

这就是我提出的（对于我的应用程序，我想要给予的努力）。需要处理两种情况：1）输入和2）删除。处理输入是更容易的部分（从以前的post修改）。处理删除更难以实现。基本上，当检测到退格时，向右移动一位小数。

处理输入：

mInputRate.addTarget(self, action: #selector(rateTextFieldChanged), for: .editingChanged)
...
@objc func rateTextFieldChanged (_ textField : UITextField){
        if let amountString = textField.text?.rateInputFormatting() {
            textField.text = amountString
            calculate()
        }
    }

和

extension String {

    // formatting text for currency textField
    func rateInputFormatting() -> String {

        var number: NSNumber!
        let formatter = NumberFormatter()
        formatter.numberStyle = .decimal
        formatter.maximumFractionDigits = 3
        formatter.minimumFractionDigits = 3
        formatter.maximum = 100
        formatter.minimum = 0

        var amountWithPrefix = self

        // remove from String: "$", ".", ","
        let regex = try! NSRegularExpression(pattern: "[^0-9]", options: .caseInsensitive)
        amountWithPrefix = regex.stringByReplacingMatches(in: amountWithPrefix, options: NSRegularExpression.MatchingOptions(rawValue: 0), range: NSMakeRange(0, self.characters.count), withTemplate: "")

        let double = (amountWithPrefix as NSString).doubleValue
        number = NSNumber(value: (double / 1000))

        // if first number is 0 or all numbers were deleted
        guard number != 0 as NSNumber else {
            return ""
        }

        return "\(formatter.string(from: number)!)%"
    }
}

这处理删除（退格）：

extension CalculatorVC : UITextFieldDelegate{
    func textField(_ textField: UITextField, shouldChangeCharactersIn range: NSRange, replacementString string: String) -> Bool {
        let  char = string.cString(using: String.Encoding.utf8)!

        let isBackSpace = strcmp(char, "\\b")

        if (isBackSpace == -92) {
            //delete the second to last character
            let text = textField.text!
            let textDouble = text.replacingOccurrences(of: "%", with: "")
            let doubleAdjusted = Double(textDouble)! / 10.0

            //pad to three decimal places
            let formatter = NumberFormatter()
            formatter.maximumFractionDigits = 3
            formatter.minimumFractionDigits = 3
            formatter.roundingMode = .down

            let num = NSNumber(value: doubleAdjusted)
            let newText = formatter.string(from: num)!
            textField.text = "\(newText)%"

        }
        return true
    }
}