swift-多个textfield 键盘下一项 切换

import UIKit

class LoginViewController:UIViewController ,UITextFieldDelegate{  

    @IBOutletweak var userName:UITextField!

    @IBOutletweak var passWord:UITextField!  

    

    overridefunc viewDidLoad() {

        super.viewDidLoad()

        // Do any additional setup after loading the view, typically from a nib.

        userName.delegate =self

        passWord.delegate =self

       

    }

    

    overridefunc didReceiveMemoryWarning() {

        super.didReceiveMemoryWarning()

        // Dispose of any resources that can be recreated.

    }

    

    overridefunc touchesEnded(touches: Set<UITouch>, withEvent event:UIEvent?) {

        userName.resignFirstResponder()

        passWord.resignFirstResponder()

    }

    

    func textFieldShouldReturn(textField:UITextField) -> Bool{

        if textField ==self.userName{

            userName.resignFirstResponder()

            passWord.becomeFirstResponder()

        } else {

            passWord.resignFirstResponder()

        }

        returntrue

    }

}