我有一个带有@propertyUIActivityIndi​​catorView*微调器的PhotoViewController类。FlickrPhotoViewController是PhotoViewController的子类，它从Flickr下载照片并告诉微调器何时开始和停止动画。每次为ViewController提供Flickr照片时都会调用“updatePhoto”:-(void)updatePhoto{//DownloadphotoandsetitNSLog("updatePhotocalled");if(self.spinner)NSLog(@"Spinnerexistsi