将 GADBannerView 置于屏幕底部

Position GADBannerView on bottom of screen

我的GADBannerView目前在顶部,如何将其位置更改为底部?

var Banner = GADBannerView(adSize: kGADAdSizeSmartBannerPortrait)  
var request:GADRequest = GADRequest()

override func viewDidLoad() {
    super.viewDidLoad()
    func showBanner() {
        Banner.hidden = false
        Banner.adUnitID = "ca-app-pub-**************"
        Banner.rootViewController = self
        Banner.delegate = self
        self.view.addSubview(Banner)
        Banner.loadRequest(request)            
        request.testDevices = [kGADSimulatorID];                
    }
}

我应该添加什么?

Banner.frame = CGRect(x:0.0,
                      y:self.view.frame.size.height - Banner.frame.size.height,
                      width:Banner.frame.size.width,
                      height:Banner.frame.size.height)