GMSPanoramaViewDelegate无法正常工作

Question

学习谷歌地图SDK iOS，想要使用GMSPanoramaViewDelegate，但它无效。

class panViewController:UIViewController,UIActionSheetDelegate,GMSPanoramaViewDelegate{
  let screenSize: CGRect = UIScreen.mainScreen().bounds
  var lat_map = 43.649615
  var lng_map = -79.39162
  var panoView : GMSPanoramaView?
  override func viewDidLoad() {
    super.viewDidLoad()
    panoView = GMSPanoramaView(frame: CGRectMake(0, 0, self.view.bounds.width, self.view.bounds.height))
    panoView!.moveNearCoordinate(CLLocationCoordinate2DMake(lat_map,lng_map))

    panoView!.delegate = self
    self.view.addSubview(panoView!)

  }

 func panoView(pano:GMSPanoramaView!, didTap point:CGPoint!){
    println("working")
  }
}

有人知道这里有什么不对吗？