将文本字段集中在swift中

Question

我在注册屏幕上有4个文本字段，我已将其设置为当用户在每个文本字段上按下一个时，下一个文本字段将被聚焦。代码如下：

func textFieldShouldReturn(textField: UITextField) -> Bool {
        if (textField == self.fNameField) {
            textField.resignFirstResponder()
            self.sNameField.becomeFirstResponder()
        }
        else if (textField == self.sNameField) {
            self.emailField.becomeFirstResponder()

        } else if (textField == self.emailField) {
            self.passwordField.becomeFirstResponder()
        }
        else{
            var thereWereErrors = checkForErrors()
            if !thereWereErrors
            {
                //conditionally segue to next screen
            }
        }

        return true
    }

在最终文本字段的返回时，我正在调用错误检查功能（如下）。在此范围内如果任何字段存在问题，我想要关注该文本字段，以便用户可以轻松地纠正它。发生的事情是带有错误的文本字段聚焦（按checkForErrors函数的指示）一秒钟，然后焦点切换回密码文本字段。我还尝试将self.passwordField.resignFirstResponder()添加到上面函数的最后一个中，这使得密码字段失去焦点，但是遇到问题的文本字段根本没有获得焦点（甚至不像以前一样）我该如何解决这个问题？

func checkForErrors() -> Bool
    {
        var errors = false
        let title = "Error"
        var message = ""
        if fNameField.text.isEmpty {
            errors = true
            message += "First name empty"
            alertWithTitle(title, message: message, ViewController: self)
            self.fNameField.becomeFirstResponder()
        }
        else if sNameField.text.isEmpty
        {
            errors = true
            message += "Surname empty"
            alertWithTitle(title, message: message, ViewController: self)
            self.sNameField.becomeFirstResponder()
        }
        else if emailField.text.isEmpty
        {
            errors = true
            message += "Email empty"
            alertWithTitle(title, message: message, ViewController: self)
            self.emailField.becomeFirstResponder()
        }
        else if !isValidEmail(emailField.text)
        {
            errors = true
            message += "Invalid Email Address"
            alertWithTitle(title, message: message, ViewController: self)
            self.emailField.becomeFirstResponder()
        }
        else if passwordField.text.isEmpty
        {
            errors = true
            message += "Password empty"
            alertWithTitle(title, message: message, ViewController: self)
            self.passwordField.becomeFirstResponder()
        }
        else if count(passwordField.text.utf16)<8
        {
            errors = true
            message += "Password must be at least 8 characters"
            alertWithTitle(title, message: message, ViewController: self)
            self.passwordField.becomeFirstResponder()
        }

        return errors
    }

注意我已经包含了textField委托。

根据要求提供标题功能的警报：

func alertWithTitle(title: String!, #message: String, #ViewController: UIViewController) {
    let alert = UIAlertController(title: title, message: message, preferredStyle: .Alert)
    let action = UIAlertAction(title: "OK", style: .Cancel, handler: nil)
    alert.addAction(action)
    ViewController.presentViewController(alert, animated: true, completion: nil)
}

Answer 1

这对我有用：

import UIKit

class ViewController:UIViewController, UITextFieldDelegate {

    @IBOutlet weak var fNameField: UITextField!
    @IBOutlet weak var sNameField: UITextField!
    @IBOutlet weak var emailField: UITextField!
    @IBOutlet weak var passwordField: UITextField!

    override func viewDidLoad() {
        super.viewDidLoad()

        fNameField.delegate = self
        sNameField.delegate = self
        emailField.delegate = self
        passwordField.delegate = self
    }

    func isValidEmail (test:String) ->Bool{
        // your email validation here...
        return true
    }

    func textFieldShouldReturn(textField: UITextField) -> Bool {
        textField.resignFirstResponder()
        if (textField == self.fNameField) {
            self.sNameField.becomeFirstResponder()
        }
        else if (textField == self.sNameField) {
            self.emailField.becomeFirstResponder()

        } else if (textField == self.emailField) {
            self.passwordField.becomeFirstResponder()
        }
        else{
            var thereWereErrors = checkForErrors()
            if !thereWereErrors
            {
                //conditionally segue to next screen
            }
        }

        return true
    }

    func checkForErrors() -> Bool
    {
        var errors = false
        let title = "Error"
        var message = ""
        if fNameField.text.isEmpty {
            errors = true
            message += "First name empty"
            alertWithTitle(title, message: message, ViewController: self, toFocus:self.fNameField)

        }
        else if sNameField.text.isEmpty
        {
            errors = true
            message += "Surname empty"
            alertWithTitle(title, message: message, ViewController: self, toFocus:self.sNameField)

            self.sNameField.becomeFirstResponder()
        }
        else if emailField.text.isEmpty
        {
            errors = true
            message += "Email empty"
            alertWithTitle(title, message: message, ViewController: self, toFocus:self.emailField)

        }
        else if !isValidEmail(emailField.text)
        {
            errors = true
            message += "Invalid Email Address"
            alertWithTitle(title, message: message, ViewController: self, toFocus:self.emailField)

        }
        else if passwordField.text.isEmpty
        {
            errors = true
            message += "Password empty"
            alertWithTitle(title, message: message, ViewController: self, toFocus:passwordField)
        }
        else if count(passwordField.text.utf16)<8
        {
            errors = true
            message += "Password must be at least 8 characters"
            alertWithTitle(title, message: message, ViewController: self, toFocus:self.passwordField)
        }

        return errors
    }

    func alertWithTitle(title: String!, message: String, ViewController: UIViewController, toFocus:UITextField) {
        let alert = UIAlertController(title: title, message: message, preferredStyle: .Alert)
        let action = UIAlertAction(title: "OK", style: UIAlertActionStyle.Cancel,handler: {_ in
            toFocus.becomeFirstResponder()
        });
        alert.addAction(action)
        ViewController.presentViewController(alert, animated: true, completion:nil)
    }

}

Answer 2

theTextFieldYouWant.becomeFirstResponder()