利用GCD和UILabel实现，代码如下

//设置登录成功提示

let label = UILabel.init(frame: CGRect.init(x: 50,y: 667 - 30 - 64 - 64,width: 375 - 100,height: 20))

label.text = "登录成功"

label.font = UIFont.systemFont(ofSize: 15)

label.backgroundColor = UIColor.gray

label.textAlignment = .center

label.layer.cornerRadius = 4

label.layer.masksToBounds = true

mtvc.view.addSubview(label)

DispatchQueue.global().async {

Thread.sleep(forTimeInterval: 2)//延时2秒执行

//回到主线程

DispatchQueue.main.async {

label.removeFromSuperview()

}

}

_ = self.navigationController?.popToViewController(mtvc,animated: true)