提取iAd横幅但不可见

Question

我试图制作iAd横幅广告。控制台说横幅已成功加载和获取，但我无法在模拟器中看到它。我在这做错了什么？

class GameViewController: UIViewController, ADBannerViewDelegate {

var banner : ADBannerView = ADBannerView()

在viewDidLoad中：

{
banner.delegate = self
banner.alpha = 0.0

 NSNotificationCenter.defaultCenter().addObserver(self, selector: "bannerViewDidLoadAd", name: "banner", object: nil)
}

func bannerViewWillLoadAd(banner: ADBannerView!) {
    println("banner tries to load")
}

func bannerViewDidLoadAd(banner: ADBannerView!) {
    println("banner successfully fetched")
    UIView.animateWithDuration(0.5, animations: {banner.alpha = 1.0})
    UIView.commitAnimations()

}

func bannerViewActionShouldBegin(banner: ADBannerView!, willLeaveApplication willLeave: Bool) -> Bool {
    return true
}

func bannerViewActionDidFinish(banner: ADBannerView!) {
    println("banner is closed")
}

func bannerView(banner: ADBannerView!, didFailToReceiveAdWithError error: NSError!) {
    println("banner failed too! Man...")
    println(error.localizedDescription)
    UIView.animateWithDuration(0.5, animations: {banner.alpha = 1.0})
}

在GameScene中

：

func iBanner() {
    NSNotificationCenter.defaultCenter().postNotificationName("banner", object: nil)
}

 override func didMoveToView(view: SKView) {
    iBanner()
 }