//监听frame改变
addObserver(self, forKeyPath: "frame", options: NSKeyValueObservingOptions.New, context: nil)
deinit
{
removeObserver(self, forKeyPath: "frame")
}
override func observeValueForKeyPath(keyPath: String?, ofObject object: AnyObject?, change: [String : AnyObject]?, context: UnsafeMutablePointer<Void>) {
}
