|
/*
* This file is part of the SDWebImage package.
* (c) Olivier Poitrey *
* For the full copyright and license information, please view the LICENSE
* file that was distributed with this source code.
*/
#import "SDWebImageManager.h"
#import // 内部类.
@interface SDWebImageCombinedOperation : NSObject @property (assign, nonatomic, getter = isCancelled) BOOL cancelled;
@property (copy, nonatomic) SDWebImageNoParamsBlock cancelBlock;
@property (strong, nonatomic) NSOperation *cacheOperation;
@end
@interface SDWebImageManager ()
@property (strong, nonatomic, readwrite) SDImageCache *imageCache;
@property (strong, nonatomic, readwrite) SDWebImageDownloader *imageDownloader;
@property (strong, nonatomic) NSMutableSet *failedURLs;
@property (strong, nonatomic) NSMutableArray *runningOperations;
@end
@implementation SDWebImageManager
// 利用disptach_once 特性生成一个单例,用烂了的方法.不赘述.
+ (id)sharedManager {
static dispatch_once_t once;
static id instance;
dispatch_once(&once, ^{
instance = [self new];
});
return instance;
}
// 初始化方法.
// 1.获得一个SDImageCache的单例.2.获取一个SDWebImageDownloader的单例.3.新建一个MutableSet来存储下载失败的url.
// 4.新建一个用来存储下载operation的可变数组.
// 为什么不用MutableArray储存下载失败的URL?
// 因为NSSet类有一个特性,就是Hash.实际上NSSet是一个哈希表,哈希表比数组优秀的地方是什么呢?就是查找速度快.查找同样一个元素,哈希表只需要通过key
// 即可取到,而数组至少需要遍历依次.因为SDWebImage里有关失败URL的业务需求是,一个失败的URL只需要储存一次.这样的话Set自然比Array更合适.
- (id)init {
if ((self = [super init])) {
_imageCache = [self createCache];
_imageDownloader = [SDWebImageDownloader sharedDownloader];
_failedURLs = [NSMutableSet new];
_runningOperations = [NSMutableArray new];
}
return self;
}
// 获取一个cache的单例
- (SDImageCache *)createCache {
return [SDImageCache sharedImageCache];
}
// 利用Image的URL生成一个缓存时需要的key.
// 这里有两种情况,第一种是如果检测到cacheKeyFilter不为空时,利用cacheKeyFilter来处理URL生成一个key.
// 如果为空,那么直接返回URL的string内容,当做key.
- (NSString *)cacheKeyForURL:(NSURL *)url {
if (self.cacheKeyFilter) {
return self.cacheKeyFilter(url);
}
else {
return [url absoluteString];
}
}
// 检测一张图片是否已被缓存.
// 首先检测内存缓存是否存在这张图片,如果已有,直接返回yes.
// 如果内存缓存里没有这张图片,那么调用diskImageExistsWithKey这个方法去硬盘缓存里找
- (BOOL)cachedImageExistsForURL:(NSURL *)url {
NSString *key = [self cacheKeyForURL:url];
if ([self.imageCache imageFromMemoryCacheForKey:key] != nil) return YES;
return [self.imageCache diskImageExistsWithKey:key];
}
// 检测硬盘里是否缓存了图片
- (BOOL)diskImageExistsForURL:(NSURL *)url {
NSString *key = [self cacheKeyForURL:url];
return [self.imageCache diskImageExistsWithKey:key];
}
// 首先生成一个用来cache 住Image的key(利用key的url生成)
// 然后检测内存缓存里是否已经有这张图片
// 如果已经被缓存,那么再主线程里回调block
// 如果没有检测到,那么调用diskImageExistsWithKey,这个方法会在异步线程里,将图片存到硬盘,当然在存图之前也会检测是否已在硬盘缓存图片.
- (void)cachedImageExistsForURL:(NSURL *)url
completion:(SDWebImageCheckCacheCompletionBlock)completionBlock {
NSString *key = [self cacheKeyForURL:url];
BOOL isInMemoryCache = ([self.imageCache imageFromMemoryCacheForKey:key] != nil);
if (isInMemoryCache) {
// making sure we call the completion block on the main queue
dispatch_async(dispatch_get_main_queue(), ^{
if (completionBlock) {
completionBlock(YES);
}
});
return;
}
[self.imageCache diskImageExistsWithKey:key completion:^(BOOL isInDiskCache) {
// the completion block of checkDiskCacheForImageWithKey:completion: is always called on the main queue, no need to further dispatch
if (completionBlock) {
completionBlock(isInDiskCache);
}
}];
}
//将图片存入硬盘
- (void)diskImageExistsForURL:(NSURL *)url
completion:(SDWebImageCheckCacheCompletionBlock)completionBlock {
NSString *key = [self cacheKeyForURL:url];
[self.imageCache diskImageExistsWithKey:key completion:^(BOOL isInDiskCache) {
// the completion block of checkDiskCacheForImageWithKey:completion: is always called on the main queue, no need to further dispatch
if (completionBlock) {
completionBlock(isInDiskCache);
}
}];
}
// 通过url建立一个operation用来下载图片.
- (id )downloadImageWithURL:(NSURL *)url
options:(SDWebImageOptions)options
progress:(SDWebImageDownloaderProgressBlock)progressBlock
completed:(SDWebImageCompletionWithFinishedBlock)completedBlock {
// Invoking this method without a completedBlock is pointless
NSAssert(completedBlock != nil, @"If you mean to prefetch the image, use -[SDWebImagePrefetcher prefetchURLs] instead");
// Very common mistake is to send the URL using NSString object instead of NSURL. For some strange reason, XCode won‘t
// throw any warning for this type mismatch. Here we failsafe this error by allowing URLs to be passed as NSString.
if ([url isKindOfClass:NSString.class]) {
url = [NSURL URLWithString:(NSString *)url];
}
// Prevents app crashing on argument type error like sending NSNull instead of NSURL
if (![url isKindOfClass:NSURL.class]) {
url = nil;
}
__block SDWebImageCombinedOperation *operation = [SDWebImageCombinedOperation new];
__weak SDWebImageCombinedOperation *weakOperation = operation;
BOOL isFailedUrl = NO;
// 创建一个互斥锁防止现在有别的线程修改failedURLs.
// 判断这个url是否是fail过的.如果url failed过的那么isFailedUrl就是true
@synchronized (self.failedURLs) {
isFailedUrl = [self.failedURLs containsObject:url];
}
// 如果url不存在那么直接返回一个block,如果url存在.那么继续进行判断.
// options与SDWebImageRetryFailed这个option进行按位与操作.判断用户的options里是否有retry这个option.
// 如果用户的options里没有retry这个选项并且isFaileUrl 是true.那么就回调一个error的block.
if (!url || (!(options & SDWebImageRetryFailed) && isFailedUrl)) {
dispatch_main_sync_safe(^{
NSError *error = [NSError errorWithDomain:NSURLErrorDomain code:NSURLErrorFileDoesNotExist userInfo:nil];
completedBlock(nil, error, SDImageCacheTypeNone, YES, url);
});
return operation;
}
// 创建一个互斥锁防止现在有别的线程修改runningOperations.
@synchronized (self.runningOperations) {
[self.runningOperations addObject:operation];
}
NSString *key = [self cacheKeyForURL:url];
// cacheOperation应该是一个用来下载图片并且缓存的operation
operation.cacheOperation = [self.imageCache queryDiskCacheForKey:key done:^(UIImage *image, SDImageCacheType cacheType) {
// 判断operation这时候有没有执行cancel操作,如果cancel掉了就把这个operation从我们的operation数组里remove掉然后return
if (operation.isCancelled) {
@synchronized (self.runningOperations) {
[self.runningOperations removeObject:operation];
}
return;
}
if ((!image || options & SDWebImageRefreshCached) && (![self.delegate respondsToSelector:@selector(imageManager:shouldDownloadImageForURL:)] || [self.delegate imageManager:self shouldDownloadImageForURL:url])) {
if (image && options & SDWebImageRefreshCached) {
dispatch_main_sync_safe(^{
// If image was found in the cache bug SDWebImageRefreshCached is provided, notify about the cached image
// AND try to re-download it in order to let a chance to NSURLCache to refresh it from server.
completedBlock(image, nil, cacheType, YES, url);
});
}
// download if no image or requested to refresh anyway, and download allowed by delegate
// 下面都是判断我们的options里包含哪些SDWebImageOptions,然后给我们的downloaderOptions相应的添加对应的SDWebImageDownloaderOptions. downloaderOptions |= SDWebImageDownloaderLowPriority这种表达式的意思等同于
// downloaderOptions = downloaderOptions | SDWebImageDownloaderLowPriority
SDWebImageDownloaderOptions downloaderOptions = 0;
if (options & SDWebImageLowPriority) downloaderOptions |= SDWebImageDownloaderLowPriority;
if (options & SDWebImageProgressiveDownload) downloaderOptions |= SDWebImageDownloaderProgressiveDownload;
if (options & SDWebImageRefreshCached) downloaderOptions |= SDWebImageDownloaderUseNSURLCache;
if (options & SDWebImageContinueInBackground) downloaderOptions |= SDWebImageDownloaderContinueInBackground;
if (options & SDWebImageHandleCookies) downloaderOptions |= SDWebImageDownloaderHandleCookies;
if (options & SDWebImageAllowInvalidSSLCertificates) downloaderOptions |= SDWebImageDownloaderAllowInvalidSSLCertificates;
if (options & SDWebImageHighPriority) downloaderOptions |= SDWebImageDownloaderHighPriority;
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;
}
// 调用imageDownloader去下载image并且返回执行这个request的download的operation
id subOperation = [self.imageDownloader downloadImageWithURL:url options:downloaderOptions progress:progressBlock completed:^(UIImage *downloadedImage, NSData *data, NSError *error, BOOL finished) {
if (weakOperation.isCancelled) {
// Do nothing if the operation was cancelled
// See #699 for more details
// if we would call the completedBlock, there could be a race condition between this block and another completedBlock for the same object, so if this one is called second, we will overwrite the new data
}
else if (error) {
dispatch_main_sync_safe(^{
if (!weakOperation.isCancelled) {
completedBlock(nil, error, SDImageCacheTypeNone, finished, url);
}
});
if (error.code != NSURLErrorNotConnectedToInternet && error.code != NSURLErrorCancelled && error.code != NSURLErrorTimedOut) {
@synchronized (self.failedURLs) {
[self.failedURLs addObject:url];
}
}
}
else {
if ((options & SDWebImageRetryFailed)) {
@synchronized (self.failedURLs) {
[self.failedURLs removeObject:url];
}
}
BOOL cacheOnDisk = !(options & SDWebImageCacheMemoryOnly);
if (options & SDWebImageRefreshCached && image && !downloadedImage) {
// Image refresh hit the NSURLCache cache, do not call the completion block
}
else if (downloadedImage && (!downloadedImage.images || (options & SDWebImageTransformAnimatedImage)) && [self.delegate respondsToSelector:@selector(imageManager:transformDownloadedImage:withURL:)]) {
dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_HIGH, 0), ^{
UIImage *transformedImage = [self.delegate imageManager:self transformDownloadedImage:downloadedImage withURL:url];
if (transformedImage && finished) {
BOOL imageWasTransformed = ![transformedImage isEqual:downloadedImage];
[self.imageCache storeImage:transformedImage recalculateFromImage:imageWasTransformed imageData:data forKey:key toDisk:cacheOnDisk];
}
dispatch_main_sync_safe(^{
if (!weakOperation.isCancelled) {
completedBlock(transformedImage, nil, SDImageCacheTypeNone, finished, url);
}
});
});
}
else {
if (downloadedImage && finished) {
[self.imageCache storeImage:downloadedImage recalculateFromImage:NO imageData:data forKey:key toDisk:cacheOnDisk];
}
dispatch_main_sync_safe(^{
if (!weakOperation.isCancelled) {
completedBlock(downloadedImage, nil, SDImageCacheTypeNone, finished, url);
}
});
}
}
if (finished) {
@synchronized (self.runningOperations) {
[self.runningOperations removeObject:operation];
}
}
}];
operation.cancelBlock = ^{
[subOperation cancel];
@synchronized (self.runningOperations) {
[self.runningOperations removeObject:weakOperation];
}
};
}
else if (image) {
dispatch_main_sync_safe(^{
if (!weakOperation.isCancelled) {
completedBlock(image, nil, cacheType, YES, url);
}
});
@synchronized (self.runningOperations) {
[self.runningOperations removeObject:operation];
}
}
else {
// Image not in cache and download disallowed by delegate
dispatch_main_sync_safe(^{
if (!weakOperation.isCancelled) {
completedBlock(nil, nil, SDImageCacheTypeNone, YES, url);
}
});
@synchronized (self.runningOperations) {
[self.runningOperations removeObject:operation];
}
}
}];
return operation;
}
- (void)saveImageToCache:(UIImage *)image forURL:(NSURL *)url {
if (image && url) {
NSString *key = [self cacheKeyForURL:url];
[self.imageCache storeImage:image forKey:key toDisk:YES];
}
}
// cancel掉所有正在执行的operation
- (void)cancelAll {
@synchronized (self.runningOperations) {
NSArray *copiedOperations = [self.runningOperations copy];
[copiedOperations makeObjectsPerformSelector:@selector(cancel)];
[self.runningOperations removeObjectsInArray:copiedOperations];
}
}
// 判断是否有正在运行的operation
- (BOOL)isRunning {
return self.runningOperations.count > 0;
}
@end
@implementation SDWebImageCombinedOperation
- (void)setCancelBlock:(SDWebImageNoParamsBlock)cancelBlock {
// check if the operation is already cancelled, then we just call the cancelBlock
if (self.isCancelled) {
if (cancelBlock) {
cancelBlock();
}
_cancelBlock = nil; // don‘t forget to nil the cancelBlock, otherwise we will get crashes
} else {
_cancelBlock = [cancelBlock copy];
}
}
- (void)cancel {
self.cancelled = YES;
if (self.cacheOperation) {
[self.cacheOperation cancel];
self.cacheOperation = nil;
}
if (self.cancelBlock) {
self.cancelBlock();
// TODO: this is a temporary fix to #809.
// Until we can figure the exact cause of the crash, going with the ivar instead of the setter
// self.cancelBlock = nil;
_cancelBlock = nil;
}
}
@end
@implementation SDWebImageManager (Deprecated)
// deprecated method, uses the non deprecated method
// adapter for the completion block
- (id )downloadWithURL:(NSURL *)url options:(SDWebImageOptions)options progress:(SDWebImageDownloaderProgressBlock)progressBlock completed:(SDWebImageCompletedWithFinishedBlock)completedBlock {
return [self downloadImageWithURL:url
options:options
progress:progressBlock
completed:^(UIImage *image, NSError *error, SDImageCacheType cacheType, BOOL finished, NSURL *imageURL) {
if (completedBlock) {
completedBlock(image, error, cacheType, finished);
}
}];
}
@end
|
