为什么在点击登录ID和密码的文本字段时图像不会更改？

Question

为什么在使用“登录ID”和“密码”命中文本字段时图像不会更改？我是iOS的新手，我不知道这个代码的问题是什么。当我想点击LogID和密码字段时，图标不会改变。有人可以告诉我如何解决这个问题。

UITextField（扩展名）

class TextField
{
    static func imgTFEmail1(tfLgnID: UITextField)
    {
        if UI_USER_INTERFACE_IDIOM() == UIUserInterfaceIdiom.pad
        {
            //Set image within username textfield
            tfLgnID.leftViewMode = .always
            imgViewLgn = UIImageView(frame: CGRect(x: tfLgnID.frame.origin.x + 3, y: tfLgnID.frame.origin.y + 20, width: 35, height: 30))
            imgViewLgn.contentMode = .scaleAspectFit
            imgLogin = UIImage(named: "user1")!
            imgViewLgn.image = imgLogin
            tfLgnID.leftView = imgViewLgn

            //Text and Placeholder Font Size Large
            let attributes = [
                NSAttributedStringKey.foregroundColor: UIColor.lightGray,
                NSAttributedStringKey.font : UIFont(name: "Avenir-Heavy", size: 25)!
            ]
            tfLgnID.attributedPlaceholder = NSAttributedString.init(string: "Login Id", attributes: attributes)

            //Label Detail increase the font weight and family
            tfLgnID.font = UIFont(name: "Avenir-Heavy", size: 28)
        }
        else if UI_USER_INTERFACE_IDIOM() == UIUserInterfaceIdiom.phone
        {
            //Set image within username textfield
            tfLgnID.leftViewMode = .always
            imgViewLgn = UIImageView(frame: CGRect(x: -5, y: 0, width: 25, height: 22))
            imgViewLgn.contentMode = .scaleAspectFit
            imgLogin = UIImage(named: "user1")!
            imgViewLgn.image = imgLogin
            tfLgnID.leftView = imgViewLgn
        }
    }

    static func imgTFPwd1(tfPwd: UITextField)
    {
        if UI_USER_INTERFACE_IDIOM() == UIUserInterfaceIdiom.pad
        {
            //Set image within password textfield
            tfPwd.leftViewMode = .always
            imgViewPwd = UIImageView(frame: CGRect(x: tfPwd.frame.origin.x + 3, y: tfPwd.frame.origin.y + 20, width: 35, height: 30))
            imgViewPwd.contentMode = .scaleAspectFit
            imgPwd = UIImage(named: "password1")!
            imgViewPwd.image = imgPwd
            tfPwd.leftView = imgViewPwd

            //Text and Placeholder Font Size Large
            let attributes = [
                NSAttributedStringKey.foregroundColor: UIColor.lightGray,
                NSAttributedStringKey.font : UIFont(name: "Avenir-Heavy", size: 25)!
            ]
            tfPwd.attributedPlaceholder = NSAttributedString.init(string: "Password", attributes: attributes)

            //Label Detail increase the font weight and family
            tfPwd.font = UIFont(name: "Avenir-Heavy", size: 28)
        }
        else if UI_USER_INTERFACE_IDIOM() == UIUserInterfaceIdiom.phone
        {
            //Set image within password textfield
            tfPwd.leftViewMode = .always
            imgViewPwd = UIImageView(frame: CGRect(x: -5, y: 0, width: 25, height: 22))
            imgViewPwd.contentMode = .scaleAspectFit
            imgPwd = UIImage(named: "password1")!
            imgViewPwd.image = imgPwd
            tfPwd.leftView = imgViewPwd
        }
    }

的ViewController

override func viewDidLayoutSubviews() {
        super.viewDidLayoutSubviews()

        //Show the horizontal line in the bottom of text fields
        self.designTextField()

        TextField.imgTFEmail1(tfLgnID: tfLgnID)
        TextField.imgTFPwd1(tfPwd: tfPwd)

    }

func textFieldDidBeginEditing(_ textField: UITextField)
    {
        //Move the screen up when tap on TextField
        self.view.frame.origin.y -= 80

        if textField == self.tfLgnID
        {
            bottomTFEmail.backgroundColor = UIColor(red: 11/255, green: 174/255, blue: 250/255, alpha: 1).cgColor

            TextField.imgTFEmail2(tfLgnID: tfLgnID)
            TextField.imgTFPwd2(tfPwd: tfPwd)

        }
        else if textField == self.tfPwd
        {
            imgPwd = UIImage(named: "password2")!

            bottomTFPwd.backgroundColor = UIColor(red: 11/255, green: 174/255, blue: 250/255, alpha: 1).cgColor
        }
    }

    func textFieldDidEndEditing(_ textField: UITextField)
    {
        self.view.frame.origin.y = 0

        if textField == self.tfLgnID
        {

            bottomTFEmail.backgroundColor = UIColor.lightGray.cgColor
            imgLogin = UIImage(named: "user1")!
            imgViewLgn.image = imgLogin
            tfLgnID.leftView = imgViewLgn

            if !(Utility.validateEmail(candidate: self.tfLgnID.text!))
            {
                let alertController = UIAlertController.alertCtrl(title: "Warning", message: "Please enter your correct email address", buttonTitle: "OK")
                self.present(alertController, animated: true, completion: nil)
            }
        }
        else if textField == self.tfPwd
        {
            bottomTFPwd.backgroundColor = UIColor.lightGray.cgColor
            imgPwd = UIImage(named: "password1")!
            imgViewPwd.image = imgPwd
            tfPwd.leftView = imgViewPwd
        }
    }

结果

没有击中

点击