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(100.0,0.0,0.0))
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()
        }
}