swift中UIActivityIndicatorView的使用

 // 实例化
 let activityview = UIActivityIndicatorView(frame: CGRectMake(10.0, 10.0, 50.0, 50.0))
 self.view.addSubview(activityview)

 activityview.backgroundColor = UIColor.yellowColor()
 activityview.activityIndicatorViewStyle = UIActivityIndicatorViewStyle.WhiteLarge
 activityview.color = UIColor.redColor()

 // 停止转圈圈时，隐藏
 activityview.hidesWhenStopped = true
 activityview.startAnimating()

 activityview.tag = 1000

 let swithch = UISwitch(frame: CGRectMake(100.0, 10.0, 0.0, 0.0))
 self.view.addSubview(swithch)
 swithch.on = false
 swithch.addTarget(self, action: Selector("switchValueChange:"), forControlEvents: UIControlEvents.ValueChanged)

 // MARK: - switchValueChange
 func switchValueChange(sender:UISwitch)
 {
         let activityview = self.view.viewWithTag(1000) as! UIActivityIndicatorView

         let openStatus = sender.on
         if openStatus
         {
             if !activityview.isAnimating()
             {
                 activityview.startAnimating()
             }
         }
         else
         {
             activityview.stopAnimating()
         }
 }