达到字符限制时切换到下一个 UITextField

Question

我需要在三个文本字段中输入电话号码。我正在尝试将每个文本字段的字符限制设置为三个字符，一旦达到此限制，就切换到新的文本字段。

我在网上看到用这个代码来限制字符：

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

    let currentCharacterCount = textField.text?.characters.count ?? 0
    if (range.length + range.location > currentCharacterCount){
        return false
    }
    let newLength = currentCharacterCount + string.characters.count - range.length
    return newLength <= 25
}

并使用它来切换到在新文本字段上输入：

.didbecomefirstresponder()

但我不确定如何将文本字段限制为 3 个字符，然后切换到下一个字段。

Answer 1

这是我的代码，我如何解决这个问题：

三个文本字段是：

@IBOutlet var txtField1: UITextField!
@IBOutlet var txtField2: UITextField!
@IBOutlet var txtField3: UITextField!

将UITextFieldDelegate 导入您的班级并将所有文本字段的委托设置为self。

并使用此方法改变焦点。

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

    let currentCharacterCount = ((textField.text?.characters.count)! + string.characters.count) - 1

    switch (textField, currentCharacterCount) {
    case (self.txtField1, 3):
        self.txtField2.becomeFirstResponder()
    case (self.txtField2, 7):
        self.txtField3.becomeFirstResponder()
    default:
        break
    }

    return true
}

在这里，我将第一个文本字段的字符数设置为 3，将第二个文本字段的字符数设置为 7。

Answer 2

您可以使用UITextField shouldChangeCharactersInRange 的委托方法。不过，您必须做一些设置工作。这是一个创建 3 个文本字段的示例，符合 UITextFieldDelegate，并且执行的操作与您所描述的类似。

class ViewController: UIViewController, UITextFieldDelegate {


var max = 3
var fields:[UITextField] = []

override func viewDidLoad() {
    super.viewDidLoad()
    // Do any additional setup after loading the view, typically from a nib.


    // This is just an example to layout 3 text fields.
    for i in 0 ..< 3 {
        let field = UITextField()
        view.addSubview(field)
        field.delegate = self
        field.borderStyle = .roundedRect
        field.font = UIFont(name: "AvenirNext-Regular", size: 15.0)
        field.textColor = UIColor.black
        field.frame = CGRect(x: view.bounds.width/2 - 100, y: 100 + (150*CGFloat(i)), width: 200, height: 50)
        fields.append(field)
    }


}

func textField(_ textField: UITextField, shouldChangeCharactersIn range: NSRange, replacementString string: String) -> Bool {
    // Make sure the field has non-nil text
    if let text = textField.text {
        // Check if the text length has reached max limit
        if text.characters.count > (max-1) {
            // Get index of field from fields array
            if let index = fields.index(of: textField) {
                // Make sure it's not the last field in the array else return false
                if index < fields.count-1 {
                    // Make the next field in the array become first responder if it's text is non-nil and it's text's character count is less than desired max
                    if fields[index+1].text != nil && fields[index+1].text!.characters.count < (max-1) {
                        fields[index+1].becomeFirstResponder()
                    } else {
                        return false
                    }
                } else {
                    return false
                }
            }
        }
    }
    return true
}

}

Answer 3

我发现 Pierce 的答案太复杂了，anas.p 的答案对我来说并不像预期的那样有效。我的 Swift 5 解决方案：

override func viewDidLoad() {
    textField1.addTarget(self, action: #selector(textFieldDidChange1), for:.editingChanged)
    textField2.addTarget(self, action: #selector(textFieldDidChange2), for:.editingChanged)
}

@objc func textFieldDidChange1() {
        // After 2 characters are typed, immediately jump to textField2
        if (textField1.text?.count == 2) {
            self.textField2.becomeFirstResponder()
        }
    }

@objc func textFieldDidChange2() {
    if (textField2.text?.count == 2) {
        self.textField3.becomeFirstResponder()
    }
}