一、具体问题
开发的过程中，发现某个界面部分图片的显示出现了问题只显示占位图片，取出图片的url在浏览器却是能打开的，各种尝试甚至找同行的朋友帮忙在他们项目里展示都会存在问题，最终发现通过第三方框架SDWebImage或者YYWebImage下载带有逗号的url图片链接都会下载失败，在下载方法完成的回调block里面打印信息如下：
Error Domain=NSURLErrorDomain Code=403 "(null)"
现列举两个不能正常展示的图片url：
http://img1.imgtn.bdimg.com/it/u=3044191397,2911599132&fm=27&gp=0.jpg
http://img2.imgtn.bdimg.com/it/u=3509004173,840437551&fm=27&gp=0.jpg
有兴趣的小伙伴可以拿到自己的项目里试试
二、问题原因
网上有小伙伴提出是因为缺少User-Agent用户代理导致的。只有设置了用户代理，才能访问到这张带有逗号的url图片。至于这个用户代理的格式，只要有值或者约定的特定格式字符串都可以。
三、具体解决
1.第三方框架YYWebImage
找到YYWebImageManager.m文件，定位到设置http请求头的属性即_headers的地方，加入一个User-Agent的键值对，具体改动可以看下面的方法
- (instancetype)initWithCache:(YYImageCache *)cache queue:(NSOperationQueue *)queue{
self = [super init];
if (!self) return nil;
_cache = cache;
_queue = queue;
_timeout = 15.0;
NSString *userAgent = @"";
userAgent = [NSString stringWithFormat:@"%@/%@ (%@; iOS %@; Scale/%0.2f)", [[[NSBundle mainBundle] infoDictionary] objectForKey:(__bridge NSString *)kCFBundleExecutableKey] ?: [[[NSBundle mainBundle] infoDictionary] objectForKey:(__bridge NSString *)kCFBundleIdentifierKey], [[[NSBundle mainBundle] infoDictionary] objectForKey:@"CFBundleShortVersionString"] ?: [[[NSBundle mainBundle] infoDictionary] objectForKey:(__bridge NSString *)kCFBundleVersionKey], [[UIDevice currentDevice] model], [[UIDevice currentDevice] systemVersion], [[UIScreen mainScreen] scale]];
if (userAgent) {
if (![userAgent canBeConvertedToEncoding:NSASCIIStringEncoding]) {
NSMutableString *mutableUserAgent = [userAgent mutableCopy];
if (CFStringTransform((__bridge CFMutableStringRef)(mutableUserAgent), NULL, (__bridge CFStringRef)@"Any-Latin; Latin-ASCII; [:^ASCII:] Remove", false)) {
userAgent = mutableUserAgent;
}
}
}
//带有逗号的图片url不显示的问题，重要的是设置代理才能解决
if (YYImageWebPAvailable()) {
_headers = @{ @"Accept" : @"image/webp,image/*;q=0.8", @"User-Agent" : userAgent};
} else {
_headers = @{ @"Accept" : @"image/*;q=0.8", @"User-Agent" : userAgent};
}
return self;
}
2.第三方框架SDWebImage
找到SDWebImageDownloader.m文件，也是定位到设置http请求头的属性即_HTTPHeaders的地方，加入一个User-Agent的键值对，具体改动可以看下面的方法
- (id)init {
if ((self = [super init])) {
_operationClass = [SDWebImageDownloaderOperation class];
_shouldDecompressImages = YES;
_executionOrder = SDWebImageDownloaderFIFOExecutionOrder;
_downloadQueue = [NSOperationQueue new];
_downloadQueue.maxConcurrentOperationCount = 6;
_URLCallbacks = [NSMutableDictionary new];
/***********************/
NSString *userAgent = @"";
userAgent = [NSString stringWithFormat:@"%@/%@ (%@; iOS %@; Scale/%0.2f)", [[[NSBundle mainBundle] infoDictionary] objectForKey:(__bridge NSString *)kCFBundleExecutableKey] ?: [[[NSBundle mainBundle] infoDictionary] objectForKey:(__bridge NSString *)kCFBundleIdentifierKey], [[[NSBundle mainBundle] infoDictionary] objectForKey:@"CFBundleShortVersionString"] ?: [[[NSBundle mainBundle] infoDictionary] objectForKey:(__bridge NSString *)kCFBundleVersionKey], [[UIDevice currentDevice] model], [[UIDevice currentDevice] systemVersion], [[UIScreen mainScreen] scale]];
if (userAgent) {
if (![userAgent canBeConvertedToEncoding:NSASCIIStringEncoding]) {
NSMutableString *mutableUserAgent = [userAgent mutableCopy];
if (CFStringTransform((__bridge CFMutableStringRef)(mutableUserAgent), NULL, (__bridge CFStringRef)@"Any-Latin; Latin-ASCII; [:^ASCII:] Remove", false)) {
userAgent = mutableUserAgent;
}
}
}
/***********************/
#ifdef SD_WEBP
_HTTPHeaders = [@{@"Accept": @"image/webp,image/*;q=0.8", userAgent : @"User-Agent"} mutableCopy];
#else
_HTTPHeaders = [@{@"Accept": @"image/*;q=0.8", userAgent : @"User-Agent"} mutableCopy];
#endif
_barrierQueue = dispatch_queue_create("com.hackemist.SDWebImageDownloaderBarrierQueue", DISPATCH_QUEUE_CONCURRENT);
_downloadTimeout = 15.0;
}
return self;
}
或者是直接在UIImageView+WebCache.m文件中，在统一下载图片入口最前面添加如下代码
- (void)sd_setImageWithURL:(NSURL *)url placeholderImage:(UIImage *)placeholder options:(SDWebImageOptions)options progress:(SDWebImageDownloaderProgressBlock)progressBlock completed:(SDWebImageCompletionBlock)completedBlock {
/***********************/
NSString *userAgent = @"";
userAgent = [NSString stringWithFormat:@"%@/%@ (%@; iOS %@; Scale/%0.2f)", [[[NSBundle mainBundle] infoDictionary] objectForKey:(__bridge NSString *)kCFBundleExecutableKey] ?: [[[NSBundle mainBundle] infoDictionary] objectForKey:(__bridge NSString *)kCFBundleIdentifierKey], [[[NSBundle mainBundle] infoDictionary] objectForKey:@"CFBundleShortVersionString"] ?: [[[NSBundle mainBundle] infoDictionary] objectForKey:(__bridge NSString *)kCFBundleVersionKey], [[UIDevice currentDevice] model], [[UIDevice currentDevice] systemVersion], [[UIScreen mainScreen] scale]];
if (userAgent) {
if (![userAgent canBeConvertedToEncoding:NSASCIIStringEncoding]) {
NSMutableString *mutableUserAgent = [userAgent mutableCopy];
if (CFStringTransform((__bridge CFMutableStringRef)(mutableUserAgent), NULL, (__bridge CFStringRef)@"Any-Latin; Latin-ASCII; [:^ASCII:] Remove", false)) {
userAgent = mutableUserAgent;
}
}
[[SDWebImageDownloader sharedDownloader] setValue:userAgent forHTTPHeaderField:@"User-Agent"];
}
/***********************/
[self sd_cancelCurrentImageLoad];
........省略原源码
}
3.其他第三方下载图片的框架
直接全局搜索字符串"Accept"，因为虽然缺少设置User-Agent用户代理，但是http请求头一般都会有设置"Accept"，所以定位后，直接再加一个User-Agent的键值对就可以了
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