UI: ScrollView

遵守了 UIScrollViewDelegate

划到那一页，标签 显示 对应的页码

func scrollViewDidEndDecelerating(scrollView: UIScrollView) {
        
        let index = Int(scrollView.contentOffset.x/scrollView.bounds.size.width)
        
        
        self.photoIndex = index
        
        
        self.titleLabel!.text = "第\(self.photoIndex! + 1)页， 共\((self.photoArray?.count)!)页"
        
        
        
        
    }