         //通过打印可以看到此时cell的frame就是我们在flowLayout中设置的结果
         print("self.collectionView:\(String(describing: self))")
         imageView = UIImageView.init(frame: self.bounds)
+        imageView?.image = UIImage.init(named: placeholder)
         imageView?.contentMode = .scaleAspectFill
         contentView.addSubview(imageView!)
     }

            }
        }
        //跳转方式一：
//        let indexpath = NSIndexPath.init(row: offset, section: 0)
//        //滚动位置
//        self.scrollToItem(at: indexpath as IndexPath, at: .left, animated: false)
        //跳转方式二：
        scrollView.contentOffset = CGPoint.init(x: CGFloat(offset) * scrollView.bounds.size.width, y: 0)
    }

    
    convenience init(frame:CGRect,imageUrls:NSArray) {
        self.init(frame: frame, collectionViewLayout: HHCollectionViewFlowLayout.init())
        imgUrls = imageUrls
    }
    
    override init(frame: CGRect, collectionViewLayout layout: UICollectionViewLayout) {
