/* * This file is part of the SDWebImage package. * (c) Olivier Poitrey * * For the full copyright and license information, please view the LICENSE * ...
/*
* 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 "SDWebImageCompat.h"
#import "SDWebImageOperation.h"
#import "SDWebImageDownloader.h"
#import "SDImageCache.h"
typedef NS_OPTIONS(NSUInteger, SDWebImageOptions) {
/**
* By default, when a URL fail to be downloaded, the URL is blacklisted so the library won't keep trying.
* This flag disable this blacklisting.
*/
/**
*預設情況下,如果一個url在下載的時候失敗了,那麼這個url會被加入黑名單並且library不會嘗試再次下載,這個flag會阻止library把失敗的url加入黑名單(簡單來說如果選擇了這個flag,那麼即使某個url下載失敗了,sdwebimage還是會嘗試再次下載他.)
*/
SDWebImageRetryFailed = 1 << 0,
/**
* By default, image downloads are started during UI interactions, this flags disable this feature,
* leading to delayed download on UIScrollView deceleration for instance.
*/
/**
*預設情況下,圖片會在交互發生的時候下載(例如你滑動tableview的時候),這個flag會禁止這個特性,導致的結果就是在scrollview減速的時候
*才會開始下載(也就是你滑動的時候scrollview不下載,你手從屏幕上移走,scrollview開始減速的時候才會開始下載圖片)
*/
SDWebImageLowPriority = 1 << 1,
/**
* This flag disables on-disk caching
*/
/*
*這個flag禁止磁碟緩存,只有記憶體緩存
*/
SDWebImageCacheMemoryOnly = 1 << 2,
/**
* This flag enables progressive download, the image is displayed progressively during download as a browser would do.
* By default, the image is only displayed once completely downloaded.
*/
/*
*這個flag會在圖片下載的時候就顯示(就像你用瀏覽器瀏覽網頁的時候那種圖片下載,一截一截的顯示(待確認))
*
*/
SDWebImageProgressiveDownload = 1 << 3,
/**
* Even if the image is cached, respect the HTTP response cache control, and refresh the image from remote location if needed.
* The disk caching will be handled by NSURLCache instead of SDWebImage leading to slight performance degradation.
* This option helps deal with images changing behind the same request URL, e.g. Facebook graph api profile pics.
* If a cached image is refreshed, the completion block is called once with the cached image and again with the final image.
*
* Use this flag only if you can't make your URLs static with embeded cache busting parameter.
*/
/*
*這個選項的意思看的不是很懂,大意是即使一個圖片緩存了,還是會重新請求.並且緩存側略依據NSURLCache而不是SDWebImage.
*
*/
SDWebImageRefreshCached = 1 << 4,
/**
* In iOS 4+, continue the download of the image if the app goes to background. This is achieved by asking the system for
* extra time in background to let the request finish. If the background task expires the operation will be cancelled.
*/
/*
*啟動後臺下載,加入你進入一個頁面,有一張圖片正在下載這時候你讓app進入後臺,圖片還是會繼續下載(這個估計要開backgroundfetch才有用)
*/
SDWebImageContinueInBackground = 1 << 5,
/**
* Handles cookies stored in NSHTTPCookieStore by setting
* NSMutableURLRequest.HTTPShouldHandleCookies = YES;
*/
/*
*可以控制存在NSHTTPCookieStore的cookies.(我沒用過,等用過的人過來解釋一下)
*/
SDWebImageHandleCookies = 1 << 6,
/**
* Enable to allow untrusted SSL ceriticates.
* Useful for testing purposes. Use with caution in production.
*/
/*
*允許不安全的SSL證書,在正式環境中慎用
*/
SDWebImageAllowInvalidSSLCertificates = 1 << 7,
/**
* By default, image are loaded in the order they were queued. This flag move them to
* the front of the queue and is loaded immediately instead of waiting for the current queue to be loaded (which
* could take a while).
*/
/*
*預設情況下,image在裝載的時候是按照他們在隊列中的順序裝載的(就是先進先出).這個flag會把他們移動到隊列的前端,並且立刻裝載
*而不是等到當前隊列裝載的時候再裝載.
*/
SDWebImageHighPriority = 1 << 8,
/**
* By default, placeholder images are loaded while the image is loading. This flag will delay the loading
* of the placeholder image until after the image has finished loading.
*/
/*
*預設情況下,占點陣圖會在圖片下載的時候顯示.這個flag開啟會延遲占點陣圖顯示的時間,等到圖片下載完成之後才會顯示占點陣圖.(等圖片顯示完了我幹嘛還顯示占點陣圖?或許是我理解錯了?)
*/
SDWebImageDelayPlaceholder = 1 << 9,
/**
* We usually don't call transformDownloadedImage delegate method on animated images,
* as most transformation code would mangle it.
* Use this flag to transform them anyway.
*/
/*
*是否transform圖片(沒用過,還要再看,但是據我估計,是否是圖片有可能方向不對需要調整方向,例如採用iPhone拍攝的照片如果不糾正方向,那麼圖片是向左旋轉90度的.可能很多人不知道iPhone的攝像頭並不是豎直的,而是向左偏了90度.具體請google.)
*/
SDWebImageTransformAnimatedImage = 1 << 10,
};
typedef void(^SDWebImageCompletionBlock)(UIImage *image, NSError *error, SDImageCacheType cacheType, NSURL *imageURL);
typedef void(^SDWebImageCompletionWithFinishedBlock)(UIImage *image, NSError *error, SDImageCacheType cacheType, BOOL finished, NSURL *imageURL);
typedef NSString *(^SDWebImageCacheKeyFilterBlock)(NSURL *url);
@class SDWebImageManager;
@protocol SDWebImageManagerDelegate @optional
/**
* Controls which image should be downloaded when the image is not found in the cache.
*
* @param imageManager The current `SDWebImageManager`
* @param imageURL The url of the image to be downloaded
*
* @return Return NO to prevent the downloading of the image on cache misses. If not implemented, YES is implied.
*/
/*
*主要作用是當緩存里沒有發現某張圖片的緩存時,是否選擇下載這張圖片(預設是yes),可以選擇no,那麼sdwebimage在緩存中沒有找到這張圖片的時候不會選擇下載
*/
- (BOOL)imageManager:(SDWebImageManager *)imageManager shouldDownloadImageForURL:(NSURL *)imageURL;
/**
* Allows to transform the image immediately after it has been downloaded and just before to cache it on disk and memory.
* NOTE: This method is called from a global queue in order to not to block the main thread.
*
* @param imageManager The current `SDWebImageManager`
* @param image The image to transform
* @param imageURL The url of the image to transform
*
* @return The transformed image object.
*/
/**
*在圖片下載完成並且還沒有加入磁碟緩存或者記憶體緩存的時候就transform這個圖片.這個方法是在非同步線程執行的,防治阻塞主線程.
*至於為什麼在非同步執行很簡單,對一張圖片糾正方向(也就是transform)是很耗資源的,一張2M大小的圖片糾正方向你可以用instrument測試一下耗時.
*很恐怖
*/
- (UIImage *)imageManager:(SDWebImageManager *)imageManager transformDownloadedImage:(UIImage *)image withURL:(NSURL *)imageURL;
@end
/**
* The SDWebImageManager is the class behind the UIImageView+WebCache category and likes.
* It ties the asynchronous downloader (SDWebImageDownloader) with the image cache store (SDImageCache).
* You can use this class directly to benefit from web image downloading with caching in another context than
* a UIView.
*
* Here is a simple example of how to use SDWebImageManager:
*
* @code
SDWebImageManager *manager = [SDWebImageManager sharedManager];
[manager downloadImageWithURL:imageURL
options:0
progress:nil
completed:^(UIImage *image, NSError *error, SDImageCacheType cacheType, BOOL finished, NSURL *imageURL) {
if (image) {
// do something with image
}
}];
* @endcode
*/
/*
*這一段是闡述SDWebImageManager是幹嘛的.其實UIImageView+WebCache這個category背後執行操作的就是這個SDWebImageManager.他會綁定一個下載器也就是SDWebImageDownloader和一個緩存SDImageCache.後面的大意應該是講你可以直接使用一個其他上下文環境的SDWebImageManager,而不是僅僅限於一個UIView.
*/
@interface SDWebImageManager : NSObject
@property (weak, nonatomic) id delegate;
/**
*如同上文所說,一個SDWebImageManager會綁定一個imageCache和一個下載器.
*/
@property (strong, nonatomic, readonly) SDImageCache *imageCache;
@property (strong, nonatomic, readonly) SDWebImageDownloader *imageDownloader;
/**
* The cache filter is a block used each time SDWebImageManager need to convert an URL into a cache key. This can
* be used to remove dynamic part of an image URL.
*
* The following example sets a filter in the application delegate that will remove any query-string from the
* URL before to use it as a cache key:
*
* @code
[[SDWebImageManager sharedManager] setCacheKeyFilter:^(NSURL *url) {
url = [[NSURL alloc] initWithScheme:url.scheme host:url.host path:url.path];
return [url absoluteString];
}];
* @endcode
*/
/*
* 這個cacheKeyFilter是幹嘛的呢?很簡單.1他是一個block.2.這個block的作用就是生成一個image的key.因為sdwebimage的緩存原理你可以當成是一個字典,每一個字典的value就是一張image,那麼這個value對應的key是什麼呢?就是cacheKeyFilter根據某個規則對這個圖片的url做一些操作生成的.上面的示例就顯示了怎麼利用這個block把image的url重新組合生成一個key.以後當sdwebimage檢測到你
*/
@property (nonatomic, copy) SDWebImageCacheKeyFilterBlock cacheKeyFilter;
/**
* Returns global SDWebImageManager instance.
*
* @return SDWebImageManager shared instance
*/
/*
*這個不用我解釋了吧,生成一個SDWebImagemanager的單例.
*/
+ (SDWebImageManager *)sharedManager;
/**
* Downloads the image at the given URL if not present in cache or return the cached version otherwise.
* 從給定的URL中下載一個之前沒有被緩存的Image.
*
* @param url The URL to the image
* @param options A mask to specify options to use for this request
* @param progressBlock A block called while image is downloading
* @param completedBlock A block called when operation has been completed.
*
* This parameter is required.
*
* This block has no return value and takes the requested UIImage as first parameter.
* In case of error the image parameter is nil and the second parameter may contain an NSError.
*
* The third parameter is an `SDImageCacheType` enum indicating if the image was retrived from the local cache
* or from the memory cache or from the network.
*
* The last parameter is set to NO when the SDWebImageProgressiveDownload option is used and the image is
* downloading. This block is thus called repetidly with a partial image. When image is fully downloaded, the
* block is called a last time with the full image and the last parameter set to YES.
*
* @return Returns an NSObject conforming to SDWebImageOperation. Should be an instance of SDWebImageDownloaderOperation
*/
/*
* 這個方法主要就是SDWebImage下載圖片的方法了.
* 第一個參數是必須要的,就是image的url
* 第二個參數就是我們上面的Options,你可以定製化各種各樣的操作.詳情參上.
* 第三個參數是一個回調block,用於圖片在下載過程中的回調.(英文註釋應該是有問題的.)
* 第四個參數是一個下載完成的回調.會在圖片下載完成後回調.
* 返回值是一個NSObject類,並且這個NSObject類是conforming一個協議這個協議叫做SDWebImageOperation,這個協議很簡單,就是一個cancel掉operation的協議.
*/
- (id )downloadImageWithURL:(NSURL *)url
options:(SDWebImageOptions)options
progress:(SDWebImageDownloaderProgressBlock)progressBlock
completed:(SDWebImageCompletionWithFinishedBlock)completedBlock;
/**
* Saves image to cache for given URL
*
* @param image The image to cache
* @param url The URL to the image
*
*/
/*
* 將圖片存入cache的方法,類似於字典的setValue: forKey:
*/
- (void)saveImageToCache:(UIImage *)image forURL:(NSURL *)url;
/**
* Cancel all current opreations
*/
/*
*取消掉當前所有的下載圖片的operation
*/
- (void)cancelAll;
/**
* Check one or more operations running
*/
/*
* check一下是否有一個或者多個operation正在執行(簡單來說就是check是否有圖片在下載)
*/
- (BOOL)isRunning;
/**
* Check if image has already been cached
*
* @param url image url
*
* @return if the image was already cached
*/
/*
* 通過一個image的url是否已經存在,如果存在返回yes,否則返回no
*/
- (BOOL)cachedImageExistsForURL:(NSURL *)url;
/**
* Check if image has already been cached on disk only
*
* @param url image url
*
* @return if the image was already cached (disk only)
*/
/*
* 檢測一個image是否已經被緩存到磁碟(是否存且僅存在disk里).
*/
- (BOOL)diskImageExistsForURL:(NSURL *)url;
/**
* Async check if image has already been cached
*
* @param url image url
* @param completionBlock the block to be executed when the check is finished
*
* @note the completion block is always executed on the main queue
*/
/*
* 如果檢測到圖片已經被緩存,那麼執行回調block.這個block會永遠執行在主線程.也就是你可以在這個回調block里更新ui.
*/
- (void)cachedImageExistsForURL:(NSURL *)url
completion:(SDWebImageCheckCacheCompletionBlock)completionBlock;
/**
* Async check if image has already been cached on disk only
*
* @param url image url
* @param completionBlock the block to be executed when the check is finished
*
* @note the completion block is always executed on the main queue
*/
/*
* 如果檢測到圖片已經被緩存在磁碟(存且僅存在disk),那麼執行回調block.這個block會永遠執行在主線程.也就是你可以在這個回調block里更新ui.
*/
- (void)diskImageExistsForURL:(NSURL *)url
completion:(SDWebImageCheckCacheCompletionBlock)completionBlock;
/**
*Return the cache key for a given URL
*/
/*
* 通過image的url返回image存在緩存里的key.有人會問了,為什麼不直接把圖片的url當做image的key來使用呢?而是非要對url做一些處理才能當做key.我的解釋是,我也不太清楚.可能為了防止重覆吧.
*/
- (NSString *)cacheKeyForURL:(NSURL *)url;
@end
#pragma mark - Deprecated
typedef void(^SDWebImageCompletedBlock)(UIImage *image, NSError *error, SDImageCacheType cacheType) __deprecated_msg("Block type deprecated. Use `SDWebImageCompletionBlock`");
typedef void(^SDWebImageCompletedWithFinishedBlock)(UIImage *image, NSError *error, SDImageCacheType cacheType, BOOL finished) __deprecated_msg("Block type deprecated. Use `SDWebImageCompletionWithFinishedBlock`");
// 已被廢棄
@interface SDWebImageManager (Deprecated)
/**
* Downloads the image at the given URL if not present in cache or return the cached version otherwise.
*
* @deprecated This method has been deprecated. Use `downloadImageWithURL:options:progress:completed:`
*/
- (id )downloadWithURL:(NSURL *)url
options:(SDWebImageOptions)options
progress:(SDWebImageDownloaderProgressBlock)progressBlock
completed:(SDWebImageCompletedWithFinishedBlock)completedBlock __deprecated_msg("Method deprecated. Use `downloadImageWithURL:options:progress:completed:`");
@end
/*
* 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 // 內部類.
@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 特性生成一個單例,用爛了的方法.不贅述.
+ (id)sharedManager {
static dispatch_once_t once;
static id instance;
dispatch_once(&once, ^{
instance = [self new];
});
return instance;
}
// 初始化方法.
// 1.獲得一個SDImageCache的單例.2.獲取一個SDWebImageDownloader的單例.3.新建一個MutableSet來存儲下載失敗的url.
// 4.新建一個用來存儲下載operation的可變數組.
// 為什麼不用MutableArray儲存下載失敗的URL?
// 因為NSSet類有一個特性,就是Hash.實際上NSSet是一個哈希表,哈希表比數組優秀的地方是什麼呢?就是查找速度快.查找同樣一個元素,哈希表只需要通過key
// 即可取到,而數組至少需要遍歷依次.因為SDWebImage里有關失敗URL的業務需求是,一個失敗的URL只需要儲存一次.這樣的話Set自然比Array更合適.
- (id)init {
if ((self = [super init])) {
_imageCache = [self createCache];
_imageDownloader = [SDWebImageDownloader sharedDownloader];
_failedURLs = [NSMutableSet new];
_runningOperations = [NSMutableArray new];
}
return self;
}
// 獲取一個cache的單例
- (SDImageCache *)createCache {
return [SDImageCache sharedImageCache];
}
// 利用Image的URL生成一個緩存時需要的key.
// 這裡有兩種情況,第一種是如果檢測到cacheKeyFilter不為空時,利用cacheKeyFilter來處理URL生成一個key.
// 如果為空,那麼直接返回URL的string內容,當做key.
- (NSString *)cacheKeyForURL:(NSURL *)url {
if (self.cacheKeyFilter) {
return self.cacheKeyFilter(url);
}
else {
return [url absoluteString];
}
}
// 檢測一張圖片是否已被緩存.
// 首先檢測記憶體緩存是否存在這張圖片,如果已有,直接返回yes.
// 如果記憶體緩存里沒有這張圖片,那麼調用diskImageExistsWithKey這個方法去硬碟緩存里找
- (BOOL)cachedImageExistsForURL:(NSURL *)url {
NSString *key = [self cacheKeyForURL:url];
if ([self.imageCache imageFromMemoryCacheForKey:key] != nil) return YES;
return [self.imageCache diskImageExistsWithKey:key];
}
// 檢測硬碟里是否緩存了圖片
- (BOOL)diskImageExistsForURL:(NSURL *)url {
NSString *key = [self cacheKeyForURL:url];
return [self.imageCache diskImageExistsWithKey:key];
}
// 首先生成一個用來cache 住Image的key(利用key的url生成)
// 然後檢測記憶體緩存里是否已經有這張圖片
// 如果已經被緩存,那麼再主線程里回調block
// 如果沒有檢測到,那麼調用diskImageExistsWithKey,這個方法會在非同步線程里,將圖片存到硬碟,當然在存圖之前也會檢測是否已在硬碟緩存圖片.
- (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);
}
}];
}
//將圖片存入硬碟
- (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);
}
}];
}
// 通過url建立一個operation用來下載圖片.
- (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;
// 創建一個互斥鎖防止現在有別的線程修改failedURLs.
// 判斷這個url是否是fail過的.如果url failed過的那麼isFailedUrl就是true
@synchronized (self.failedURLs) {
isFailedUrl = [self.failedURLs containsObject:url];
}
// 如果url不存在那麼直接返回一個block,如果url存在.那麼繼續進行判斷.
// options與SDWebImageRetryFailed這個option進行按位與操作.判斷用戶的options里是否有retry這個option.
// 如果用戶的options里沒有retry這個選項並且isFaileUrl 是true.那麼就回調一個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;
}
// 創建一個互斥鎖防止現在有別的線程修改runningOperations.
@synchronized (self.runningOperations) {
[self.runningOperations addObject:operation];
}
NSString *key = [self cacheKeyForURL:url];
// cacheOperation應該是一個用來下載圖片並且緩存的operation
operation.cacheOperation = [self.imageCache queryDiskCacheForKey:key done:^(UIImage *image, SDImageCacheType cacheType) {
// 判斷operation這時候有沒有執行cancel操作,如果cancel掉了就把這個operation從我們的operation數組裡remove掉然後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
// 下麵都是判斷我們的options里包含哪些SDWebImageOptions,然後給我們的downloaderOptions相應的添加對應的SDWebImageDownloaderOptions. downloaderOptions |= SDWebImageDownloaderLowPriority這種表達式的意思等同於
// 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;
}
// 調用imageDownloader去下載image並且返回執行這個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掉所有正在執行的operation
- (void)cancelAll {
@synchronized (self.runningOperations) {
NSArray *copiedOperations = [self.runningOperations copy];
[copiedOperations makeObjectsPerformSelector:@selector(cancel)];
[self.runningOperations removeObjectsInArray:copiedOperations];
}
}
// 判斷是否有正在運行的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
下麵來簡單的解釋一下OC里枚舉的兩種類型.
NS_ENUM和NS_OPTIONS
本質上是一樣的都是枚舉.
我舉個例子.
typedef NS_ENUM(NSInteger, UIViewAnimationTransition) {
UIViewAnimationTransitionNone,
UIViewAnimationTransitionFlipFromLeft,
UIViewAnimationTransitionFlipFromRight,
UIViewAnimationTransitionCurlUp,
UIViewAnimationTransitionCurlDown,
};
typedef NS_OPTIONS(NSUInteger, UIViewAutoresizing) {
UIViewAutoresizingNone = 0,
UIViewAutoresizingFlexibleLeftMargin = 1 << 0,
UIViewAutoresizingFlexibleWidth = 1 << 1,
UIViewAutoresizingFlexibleRightMargin = 1 << 2,
UIViewAutoresizingFlexibleTopMargin = 1 << 3,
UIViewAutoresizingFlexibleHeight = 1 << 4,
UIViewAutoresizingFlexibleBottomMargin = 1 << 5
};
應該可以看出一些苗頭.
NS_ENUM這種聲明出來的東西大部分是單選. NS_OPTIONS聲明出來的大部分是多選.
像UIViewAnimationTransition這種在用的時候肯定是只能選一種效果,你要麼從左翻到右,要麼從右翻到左,你做動畫的時候總不能同一時刻讓他同時從左到右,又從右到左翻,對吧.
而UIViewAutosizing就不一樣了.我要是讓子view的寬高和父View一樣,那麼autoviewsizing的選項肯定是類似於這種.UIViewAutoresizingFlexibleWidth | UIViewAutoresizingFlexibleHeight
沒錯吧,意思就是兩個options的我都得選才行.
那麼如果有個場景讓我判斷當前的view的Autoresizing有哪幾個.我怎麼判斷呢?
很簡單.用按位與操作就行了.
假設 autoResizings = UIViewAutoresizingFlexibleLeftMargin | UIViewAutoresizingFlexibleWidth | UIViewAutoresizingFlexibleRightMargin;
我們判斷autoResizings里是否有UIViewAutoresizingFlexibleLeftMargin的時候只需要if(autoResizings & UIViewAutoresizingFlexibleLeftMargin)是否為true就可以了.
用二進位表示的話(這裡不用care NSUInteger到底是幾位的.就表示這麼個意思)
UIViewAutoresizingFlexibleLeftMargin = 00000001
UIViewAutoresizingFlexibleWidth = 00000010
UIViewAutoresizingFlexibleRightMargin = 00000100
所以根據上面的表達式,我們的autoResizings = 00000111.
那麼執行按位與操作是這樣的.
00000111
&00000001
結果就是00000001,為true.表示含有這個選項.
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