2

所以我试图在这个应用程序中遵循 mvc 架构。这是图像部分的代码。

模型

   import Alamofire
   import AlamofireImage

    class Brands {
    private var _image : UIImage!
    var image : UIImage {
        if _image == nil {
           _image = UIImage(named: "loadingImage")
        }
        return _image
    }

    init(BrandsDict : Dictionary<String, AnyObject>){
      if let imageUrl = BrandsDict["imageUrl"] as? String{
         Alamofire.request(imageUrl).responseImage(completionHandler: { (response) in
                    guard let image = response.result.value else {
                        self._image = UIImage(named: "loadingImage")
                        return
                    }
                    self._image = image

                 })
       }else {
       self._image = UIImage(named : "loadingImage")
    }

看法

class BrandsCVCell : UICollectionViewCell {
  @IBOutlet weak var BrandImage : UIImageView!

  var brand : Brands!

  func configureCell(_ brand : Brands){
   self.brand = brand
   BrandImage.image = self.brand.image
}
}

控制器

在ViewDidLoad ....

if let jsonArray = data as? NSArray {
                for objects in jsonArray {
                    let Brand = Brands(BrandsDict: objects as! Dictionary<String, AnyObject>)
                    self.Brands.append(Brand)
                }
               self.bestBrandCollection.reloadData()
            }

....

if collectionView == BrandCollection {
 if let cell = collectionView.dequeueReusableCell(withReuseIdentifier: "BrandsCell", for: indexPath) as? BrandCollectionViewCell {

                let Brand = Brands[indexPath.row]
                cell.configureCell(Brand)
                return cell
            }else {
                return UICollectionViewCell()
            }
}

问题是，当图像加载到集合视图中时，显示的单元格不会获得下载的图像，但是当我滚动它们时，较早的单元格会获得它们的图像。有人可以帮我在下载图像后延迟加载图像。（也许是完成处理程序，但我不知道把它放在哪里）。编码答案将不胜感激。

4

1 回答 1

1

问题是从网络下载的图像在下载后没有刷新到单元格。您需要在Alamofire.request块中回调。解决方案：

首先，将块添加到模型中的回调：

class Brands {
    //......
    public var imageDidDownload:(()->Void)?  //Key point, declare a callback block

    init(BrandsDict : Dictionary<String, AnyObject>){
        if let imageUrl = BrandsDict["imageUrl"] as? String{
            Alamofire.request(imageUrl).responseImage(completionHandler: { (response) in
                //......
                self._image = image
                self.imageDidDownload?() //Key point, callback after image downloaded
                //......
            })
        }else {
            //......
        }
    }
}

二、在cell中，处理图片下载回调刷新图片：

class BrandsCVCell : UICollectionViewCell {
    //......
    func configureCell(_ brand : Brands){
        self.brand = brand
        self.brand.imageDidDownload = { [weak self]() -> Void in
            self?.BrandImage.image = self?.brand.image  //Key point, refresh image to the imageView after downloading.
        } 
        BrandImage.image = self.brand.image
    }
}

试试吧，应该可以的。

于 2017-06-02T05:28:29.123 回答