ios - 想知道在文本字段编辑 ios 期间按下键盘后退按钮时的任何时间

Question

在 OTP 中，使用了四个文本字段。按下键盘后退按钮时将光标移动到上一个文本字段？

Answer 1

To detect the backspace event in a UITextField, first you need to set up a delegate for the UITextField and set it to self.

 class ViewController: UIViewController,UITextFieldDelegate

 self.textField.delegate = self

Then you use the delegate method below to detect if a backspace was pressed

func textField(_ textField: UITextField, shouldChangeCharactersIn range: NSRange, replacementString string: String) -> Bool {

 func textField(_ textField: UITextField, shouldChangeCharactersIn range: NSRange, replacementString string: String) -> Bool {

    let char = string.cString(using: String.Encoding.utf8)
    let isBackSpace: Int = Int(strcmp(char, "\u{8}"))
    if isBackSpace == -8 {
        print("Backspace was pressed")
    }
            return true
}

Basically this method detects which button you are pressing (or have just pressed). This input comes in as an NSString. We convert this NSString to a C char type and then compare it to the traditional backspace character (\u{8}). Then if this strcmp is equal to -8, we can detect it as a backspace.

选择 2

func textField(_ textField: UITextField, shouldChangeCharactersIn range: NSRange, replacementString string: String) -> Bool {

    if (string.characters.count ) == 0 {
        //Delete any cases
        if range.length > 1 {
            //Delete whole word
        }
        else if range.length == 1 {
            //Delete single letter
        }
        else if range.length == 0 {
            //Tap delete key when textField empty
        }
    }
   return true
 }