         }
     }
     
+    //默认图片
+    private var placeholder: UIImage?{
+        willSet(newValue){
+            self.placeholder = newValue
+        }
+    }
+    
     //设置定时器的时间间隔
     public var TimeInterval: Double = 3.0{
         willSet(newValue){

        pageControl = UIPageControl()
        switch(pageControlMode){
        case .Left:
            pageControl = UIPageControl(frame: CGRectMake(10, contentScrollView.frame.origin.y + contentScrollView.frame.size.height - 30, 20 * CGFloat(imageArray.count), 20))
        case .Center:
            pageControl = UIPageControl(frame: CGRectMake((screen_width - 20 * CGFloat(imageArray.count)) / 2, contentScrollView.frame.origin.y + contentScrollView.frame.size.height - 30, 20 * CGFloat(imageArray.count), 20))
        case .Right:
            pageControl = UIPageControl(frame: CGRectMake(screen_width - 10 - 20 * CGFloat(imageArray.count), contentScrollView.frame.origin.y + contentScrollView.frame.size.height - 30, 20 * CGFloat(imageArray.count), 20))
        }
        pageControl.numberOfPages = imageArray.count;
        pageControl.hidesForSinglePage = true
        pageControl.pageIndicatorTintColor = pageControlTintColor
        pageControl.currentPageIndicatorTintColor = currentPageControlColor

    //MARK:设置属性
    
    //设置数组
    var imageArray:[String]!{
        //监听图片数组的变化，如果有变化立即刷新轮播图中显示的图片
        willSet(newValue){
            self.imageArray = newValue
