斯威夫特：如何理解下载的图像是空的？

Question

我用翠鸟下载图像，但有时图像存在，但为空。

示例：Sample Image 如何检测此类图像？

我的下载方式：

func downloadFrom(link: String, contentMode mode: UIView.ContentMode = .scaleAspectFit, rounded: Bool = false, loader: IndicatorType = .none) {
        self.kf.indicatorType = loader
        guard let url = URL(string: link) else {
            return
        }
        let img = self.image

        if(rounded) {
            let roundedProcessor = RoundCornerImageProcessor(cornerRadius: 100, targetSize: CGSize(width: 200, height: 200), roundingCorners: .all, backgroundColor: nil)
            self.kf.setImage(with: url, placeholder: img, options: [.processor(roundedProcessor)], completionHandler: {
                (image, error, cacheType, imageUrl) in

                if (error == nil) {
                    DispatchQueue.main.async() { () -> Void in
                        if (self.contentMode != UIView.ContentMode.scaleAspectFit) {
                            self.contentMode = mode
                        }
                    }
                }
            })
        } else {
            self.kf.setImage(with: url, placeholder: img, completionHandler: {
                (image, error, cacheType, imageUrl) in

                if (error == nil) {
                    DispatchQueue.main.async() { () -> Void in
                        if (self.contentMode != UIView.ContentMode.scaleAspectFit) {
                            self.contentMode = mode
                        }
                    }
                }
            })
        }
    }

Answer 1

见以下代码，从服务器获取图像后检查图像大小。如果文件大小为 0，则图像为空。

self.kf.setImage(with: url, placeholder: img, options: [.processor(roundedProcessor)], completionHandler: {
                (image, error, cacheType, imageUrl) in

  if let imageData = UIImagePNGRepresentation(image) {
     let bytes = imageData.count
        if  bytes > 0 {
            //getting image successfully
        }else{
            //Image size is 0 (image is empty)
        }
  }else{
    //Not getting image
  }
})