声明：var activityLoadingView:UIActivityIndicatorView!

//显示正在加载的控件

//初始化方式一

activityLoadingView = UIActivityIndicatorView(frame: CGRectMake(self.view.frame.size.width/2-25,self.view.frame.size.height/2,50,50))

self.view.addSubview(activityLoadingView)

activityLoadingView.color = UIColor.redColor()

activityLoadingView.backgroundColor = UIColor.grayColor()

activityLoadingView.alpha = 0.5;

//开始加载

activityLoadingView.startAnimating()

//加载完成

activityLoadingView.stopAnimating()