ios 13 获取keyWindow

swift 写法 如下

  if let window = UIApplication.shared.windows.first(where: { (wd) -> Bool in
            if wd.isKeyWindow
            {
                return true
            }
            else
            {
                return false
            }
            
        }){
            self.frame = UIScreen.main.bounds
            window.addSubview(self)
        }