Question

我想要显示imageview的背景颜色，直到下载正在进行，如果下载失败或图像不可用，那么我想显示一个占位符图像。我怎样才能做到这一点？

主要目标是稍后不在加载过程中设置图像。

由于

Answer 1

来自SDWebImage Documentation：

使用块

使用块，您可以收到有关图像下载进度的通知   每当图像检索成功完成时：

// Here we use the new provided sd_setImageWithURL: method to load the web image

对于Swift：

cell.imageView.sd_setImageWithURL(url, placeholderImage:nil, completed: { (image, error, cacheType, url) -> Void in
            if (error) {
                // set the placeholder image here

            } else {
                // success ... use the image
            }
        })

for Objective-C

    [cell.imageView sd_setImageWithURL:[NSURL URLWithString:@"http://www.domain.com/path/to/image.jpg"]
                      placeholderImage:nil
                             completed:^(UIImage *image, NSError *error, SDImageCacheType cacheType, NSURL *imageURL) {
                                    if (error) {
                                      self.imageView.image = [UIImage imageNamed:@"placeHolderImage"];
                                    }
                                 }];

Answer 2

Swift 3的解决方案：

cell.imageView?.sd_setImage(with: url) { (image, error, cache, urls) in
            if (error != nil) {
                cell.imageView.image = UIImage(named: "ico_placeholder")
            } else {
                cell.imageView.image = image
            }
}

目标C的解决方案：

[cell.imageView sd_setImageWithURL:url
                  placeholderImage:nil
                         completed:^(UIImage *image, NSError *error, SDImageCacheType cacheType, NSURL *imageURL) {
                                if (error) {
                                  self.imageView.image = [UIImage imageNamed:@"ico_placeholder"];
                                } else {
                                  self.imageView.image = image;
                                }
}];

希望你们觉得这很有用。

Answer 3

您可以将nil传递给占位符属性并自行处理完成块。

像这样：

    [self.imageView sd_setImageWithURL:self.imageURL
                  placeholderImage:nil
                           options:nil
                          progress:nil
                         completed:^(UIImage *image, NSError *error, SDImageCacheType cacheType, NSURL *imageURL) {
                             if(!error) {
                                 self.imageView.image = image;
                             } else {
                                 self.imageView.image = [UIImage imageNamed:@"placeHolder"];
                             }
                             }];

我没试过。试试看，告诉我这是否适合你。

Answer 4

在这里，这是用于分隔加载/错误图像的扩展。 loadingImage将是SDWebImage称为placeholderImage的东西。加载错误时，errorImage将是真正的占位符。

import Foundation
import SDWebImage

extension UIImageView {
    /// Separated loader and error images, short version.
    func zap_setImage(with url: URL?, loadingImage: UIImage?, errorImage: UIImage) {
        self.zap_setImage(with: url, loadingImage: loadingImage, errorImage: errorImage, completed: nil)
    }

    /// Separated loader and error images, long version.
    func zap_setImage(with url: URL?, loadingImage: UIImage?, errorImage: UIImage, completed: SDExternalCompletionBlock?) {
        self.sd_setImage(with: url, placeholderImage: loadingImage, options: []) { [weak self] (uiimage: UIImage?, error: Error?, sdimagecachetype: SDImageCacheType, usedurl: URL?) in
            //print("ISSUE1688 uiimage: \(String(describing: uiimage)), error: \(String(describing: error))")

            let setErrorImage: Bool
            switch error {
            case .none:
                // No error?
                if uiimage == nil {
                    // No error, but no image, so use error image
                    setErrorImage = true
                }
                else {
                    setErrorImage = false
                }
                break
            case .some(_):
//          case .some(let errorvalue):
                // Error?
                //print("ISSUE1688 errorvalue: \(errorvalue)")
                setErrorImage = true
                break
            }

            //print("ISSUE1688 setErrorImage: \(setErrorImage)")
            if setErrorImage {
                self?.image = errorImage
            }

            if let c = completed {
                c(uiimage, error, sdimagecachetype, usedurl)
            }
        }
    }
}

Answer 5

您可以使用它。

cell.img_UserProfile.sd_setImage(with: URL.init(string: "\(BaseURL_Image)\(image)"), placeholderImage: #imageLiteral(resourceName: "Group 1131"), options: .highPriority, context: [:])

Answer 6

使用'SDWebImage'，'〜> 4.0' 使用此imageview扩展名

top: 0

仅当图像无法加载SDWebImage时才设置占位符图像

6 个答案: