直接code！

加载图片时用的方法如下：

[self.imageView sd_setImageWithURL:[NSURL URLWithString:urlStr]];

加载不出来最新的图片，改用下面的方法，去解决问题：

[self.imageView sd_setImageWithURL:[NSURL URLWithString:urlStr] placeholderImage:nil options:SDWebImageRefreshCached];

除了上面的修改之外，我们还需要在SDWebImage的内部，SDWebImageManager.m文件中，大概180行左右吧，把之前的代码：

if (image && options & SDWebImageRefreshCached) {
    // force progressive off if image already cached but forced refreshing
    downloaderOptions &= ~SDWebImageDownloaderProgressiveDownload;
    // ignore image read from NSURLCache if image if cached but force refreshing
    downloaderOptions |= SDWebImageDownloaderIgnoreCachedResponse;
}

更换成如下：

if (image && options & SDWebImageRefreshCached) {
    // force progressive off if image already cached but forced refreshing
    downloaderOptions &= ~SDWebImageDownloaderProgressiveDownload;
替换下面
    // remove SDWebImageDownloaderUseNSURLCache flag
    downloaderOptions &= ~SDWebImageDownloaderUseNSURLCache;
替换上面
    // ignore image read from NSURLCache if image if cached but force refreshing
    downloaderOptions |= SDWebImageDownloaderIgnoreCachedResponse;
}

好久没有写更新了，以后要坚持啊！