ios - 使用Swift自动在UITextField之间切换

我有4个UITextFields在一个UIView中，就像这样：

每个UITextField限制为4个字符。我想用每个UITextFields的计数字符实现UITextField之间的自动切换。
我使用shouldChangeCharactersIn作为限制字符：

func textField(_ textField: UITextField, shouldChangeCharactersIn range: NSRange, replacementString string: String) -> Bool {
        let maxLength = 4
        var newString = String()
        let currentString: NSString = textField.text! as NSString
        newString = currentString.replacingCharacters(in: range, with: string)

        return newString.length <= maxLength
    }

这是我的开关装置：

func textFieldDidChange(_ textField: UITextField){

    let text = textField.text

    if text?.utf16.count == 4 {
        switch textField {
        case firstPartTextField:
            secondPartTextField.becomeFirstResponder()
        case secondPartTextField:
            thirdPartTextField.becomeFirstResponder()
        case thirdPartTextField:
            fourthPartTextField.becomeFirstResponder()
        default:
            break
        }
    }
}

我的问题是在删除文本时切换到以前的UITextField，当UITextField为空时，我无法检测到退格事件。

最佳答案

在viewDidLoad（）中为textField添加目标

firstTxt.addTarget(self, action: #selector(textFieldDidChange(textField:)), for: UIControlEvents.editingChanged)
    secTxt.addTarget(self, action: #selector(textFieldDidChange(textField:)), for: UIControlEvents.editingChanged)
    thirdTxt.addTarget(self, action: #selector(textFieldDidChange(textField:)), for: UIControlEvents.editingChanged)
    fourTXt.addTarget(self, action: #selector(textFieldDidChange(textField:)), for: UIControlEvents.editingChanged)

创建选择器方法
func textFieldDidChange（文本字段：UITextField）{

    let text = textField.text

    if text?.utf16.count == 1{
        switch textField{
        case firstTxt:
            secTxt.becomeFirstResponder()
        case secTxt:
            thirdTxt.becomeFirstResponder()
        case thirdTxt:
            fourTXt.becomeFirstResponder()
        case fourTXt:
            fourTXt.resignFirstResponder()
        default:
            break
        }
    }else{

    }
}

关于ios - 使用Swift自动在UITextField之间切换，我们在Stack Overflow上找到一个类似的问题：https://stackoverflow.com/questions/41912690/