这个类内容比较简单,api也都 通俗易懂,仅仅把注释贴上来即可,深究为什么这么简单,其实还是因为这个类做的事情其实仅仅是统一的调用
YYMemoryCache,YYMemoryCache来存取图片而已,具体的存储细节都实现在YYCache里面了,所以这里使用起来才会简单轻松.
先看开放了哪些api,都是什么意思
///图片缓存类型typedef NS_OPTIONS(NSUInteger, YYImageCacheType) { /// No value. YYImageCacheTypeNone = 0, /// Get/store image with memory cache.//从内存中获取 YYImageCacheTypeMemory = 1 << 0, /// Get/store image with disk cache.//从磁盘中获取 YYImageCacheTypeDisk = 1 << 1, /// Get/store image with both memory cache and disk cache.//同时获取 YYImageCacheTypeAll = YYImageCacheTypeMemory | YYImageCacheTypeDisk,};/** * YYImageCache是一个用来存储UIImage和image数据的缓存,是基于内存缓存与磁盘缓存实现的 @discussion 磁盘缓存会尝试保护原始的图片数据 如果原始的图片仍是image,会保存为一个png或者jpeg 如果原始图片是一个gif,apng,webp动图,会保存为原始格式 如果原始图片缩放比例不是1,那么缩放值会被保存为一个缩放的数据 虽然图片能被NSCoding协议解码,但是这不是一个最优解: 苹果的确使用UIImagePNGRepresentation()来解码所有类型的图片,但是可能会丢失原始的可变帧数据.结果就是打包成plist文件不能直接查看照片.如果图片没有alpha通道,使用JPEG代理PNG能够保存更多的尺寸和编解码时间. */@interface YYImageCache : NSObject//缓存名字,默认为nil@property (copy) NSString *name;//内存缓存,具体信息看YYMemoryCache@property (strong, readonly) YYMemoryCache *memoryCache;//磁盘缓存,具体信息看YYDiskCache@property (strong, readonly) YYDiskCache *diskCache;/** * 当从磁盘缓存请求图片的时候是否解码动图,默认为YES @discussion 当从磁盘缓存读取图片,会使用YYImage来解码比如WebP/APNG/GIF格式的动图,设置这个值为NO可以忽略动图 */@property (assign) BOOL allowAnimatedImage;/** * 是否解码图片存储位图,默认为YES @discussion 如果这个值为YES,图片会通过位图解码来获得更好的用户体验,但是可能会消耗更大的内存资源 */@property (assign) BOOL decodeForDisplay;- (instancetype)init UNAVAILABLE_ATTRIBUTE;+ (instancetype)new UNAVAILABLE_ATTRIBUTE;/** * 单例类初始化方法 */+ (instancetype)sharedCache;/** * 初始化方法,在多个情况下访问同一个路径会导致缓存不稳定 * * @param path cache读写的全路径,只初始化一次,你不应该来读写这个路径 * * @return 一个新的缓存对象,或者返回带nil带error信息 */- (instancetype)initWithPath:(NSString *)path NS_DESIGNATED_INITIALIZER;/** * 把图片通过一个具体的key存进缓存,同时memory跟disk都会存,这个方法会立刻返回,在后台线程执行 * * @param image 如果为nil这个方法无效 * @param key 存储图片的key,为nil这个方法无效 */- (void)setImage:(UIImage *)image forKey:(NSString *)key;/** * 通过一个key把图片缓存,这个方法会立刻返回并在后台执行 如果'type'包括'YYImageCacheTypeMemory',那么图片会被存进memory,如果image为nil会用'imageData'代理 如果'type'包括'YYImageCacheTypeDisk',那么'imageData'会被存进磁盘缓存,如果'imageData'为nil会用image代替 //这里可以看到作者一个思想,如果存进memory,直接存image,会减小很多解码的消耗,如果存disk,会存imageData * */- (void)setImage:(UIImage *)image imageData:(NSData *)imageData forKey:(NSString *)key withType:(YYImageCacheType)type;/** * 通过key移除cache中的一个图片,memory跟disk会同时移除 这个方法会立刻返回并在后台线程执行 * * @param key 移除图片用的key,为nil的话这个方法没啥用 */- (void)removeImageForKey:(NSString *)key;/** * 从缓存中通过key删图片 这个方法会立刻返回并在后台线程执行 * * @param key key * @param type 从哪删除,跟上个方法不同,这个可以删除指定类型的缓存 */- (void)removeImageForKey:(NSString *)key withType:(YYImageCacheType)type;/** * 通过key检查缓存中是否有某个图片 如果图片不在内存中,这个方法可能会阻塞线程,知道这个文件读取完毕 * * @param key key,为nil时返回NO * */- (BOOL)containsImageForKey:(NSString *)key;/** * 跟上个差不多,只不过可以查具体类型的缓存 */- (BOOL)containsImageForKey:(NSString *)key withType:(YYImageCacheType)type;/** * 通过key获取图片,如果图片不在内存中,这个方法可能会阻塞线程知道文件读取完毕 * * @param key 一个字符串类型图片缓存key,为nil方法返回nil * * @return 通过key查到的图片,没有图片就是nil */- (UIImage *)getImageForKey:(NSString *)key;/** * 跟上个方法差不多,只不过从指定缓存类型中获取图片 */- (UIImage *)getImageForKey:(NSString *)key withType:(YYImageCacheType)type;/** * 通过key异步的获取图片 * * @param key key * @param type 缓存类型 * @param block 完成的block回调,主线程调用的 */- (void)getImageForKey:(NSString *)key withType:(YYImageCacheType)type withBlock:(void(^)(UIImage *image, YYImageCacheType type))block;/** * 通过key查找图片数据data格式,方法会阻塞主线程知道文件读取完毕 * * @param key key * * @return 图片数据,查不到为nil */- (NSData *)getImageDataForKey:(NSString *)key;/** * 通过key来异步的获取图片数据 * * @param key <#key description#> * @param block 主线程的完成回调 */- (void)getImageDataForKey:(NSString *)key withBlock:(void(^)(NSData *imageData))block;其实现细节如下:
static inline dispatch_queue_t YYImageCacheIOQueue() { #ifdef YYDispatchQueuePool_h return YYDispatchQueueGetForQOS(NSQualityOfServiceDefault);#else return dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0);#endif}static inline dispatch_queue_t YYImageCacheDecodeQueue() { #ifdef YYDispatchQueuePool_h return YYDispatchQueueGetForQOS(NSQualityOfServiceUtility);#else return dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_LOW, 0);#endif}@interface YYImageCache ()- (NSUInteger)imageCost:(UIImage *)image;- (UIImage *)imageFromData:(NSData *)data;@end@implementation YYImageCache/** * 图片消耗 */- (NSUInteger)imageCost:(UIImage *)image { CGImageRef cgImage = image.CGImage; if (!cgImage) return 1; CGFloat height = CGImageGetHeight(cgImage); size_t bytesPerRow = CGImageGetBytesPerRow(cgImage); NSUInteger cost = bytesPerRow * height; if (cost == 0) cost = 1; return cost;}/** * 通过data转换为image */- (UIImage *)imageFromData:(NSData *)data { NSData *scaleData = [YYDiskCache getExtendedDataFromObject:data]; CGFloat scale = 0; if (scaleData) { scale = ((NSNumber *)[NSKeyedUnarchiver unarchiveObjectWithData:scaleData]).doubleValue; } if (scale <= 0) scale = [UIScreen mainScreen].scale; UIImage *image; if (_allowAnimatedImage) { image = [[YYImage alloc] initWithData:data scale:scale]; if (_decodeForDisplay) image = [image yy_imageByDecoded]; } else { YYImageDecoder *decoder = [YYImageDecoder decoderWithData:data scale:scale]; image = [decoder frameAtIndex:0 decodeForDisplay:_decodeForDisplay].image; } return image;}#pragma mark Public/** * 单例类的初始化方法 */+ (instancetype)sharedCache { static YYImageCache *cache = nil; static dispatch_once_t onceToken; dispatch_once(&onceToken, ^{ NSString *cachePath = [NSSearchPathForDirectoriesInDomains(NSCachesDirectory, NSUserDomainMask, YES) firstObject]; //拼接路径 cachePath = [cachePath stringByAppendingPathComponent:@"com.ibireme.yykit"]; cachePath = [cachePath stringByAppendingPathComponent:@"images"]; cache = [[self alloc] initWithPath:cachePath]; }); return cache;}- (instancetype)init { @throw [NSException exceptionWithName:@"YYImageCache init error" reason:@"YYImageCache must be initialized with a path. Use 'initWithPath:' instead." userInfo:nil]; return [self initWithPath:nil];}/** * 在初始化的时候同时初始化内存缓存跟磁盘缓存 * */- (instancetype)initWithPath:(NSString *)path { //在调用父类init之前先初始化一个内存缓存跟磁盘缓存 YYMemoryCache *memoryCache = [YYMemoryCache new];//生成内存缓存 memoryCache.shouldRemoveAllObjectsOnMemoryWarning = YES;//内存警告的时候删除所有内容 memoryCache.shouldRemoveAllObjectsWhenEnteringBackground = YES;//进入后台删除所有内容 memoryCache.countLimit = NSUIntegerMax;//不予限制 memoryCache.costLimit = NSUIntegerMax;//不予限制 memoryCache.ageLimit = 12 * 60 * 60;//cache存在的时间限制设置为12个小时 YYDiskCache *diskCache = [[YYDiskCache alloc] initWithPath:path];//生成磁盘缓存 diskCache.customArchiveBlock = ^(id object) { return (NSData *)object; };//自己来archive数据 diskCache.customUnarchiveBlock = ^(NSData *data) { return (id)data; };//自己unarchive数据 if (!memoryCache || !diskCache) return nil;//如果有任意一个初始化失败,返回nil self = [super init]; _memoryCache = memoryCache; _diskCache = diskCache; _allowAnimatedImage = YES; _decodeForDisplay = YES; return self;}- (void)setImage:(UIImage *)image forKey:(NSString *)key { [self setImage:image imageData:nil forKey:key withType:YYImageCacheTypeAll];}- (void)setImage:(UIImage *)image imageData:(NSData *)imageData forKey:(NSString *)key withType:(YYImageCacheType)type { //在每一个方法执行前先检查参数的有效性,非常好的习惯 if (!key || (image == nil && imageData.length == 0)) return; __weak typeof(self) _self = self; //如果类型有YYImageCacheTypeMemory if (type & YYImageCacheTypeMemory) { // add to memory cache if (image) { if (image.yy_isDecodedForDisplay) { //开启了位图解码的话直接把图片丢进内存缓存里面咯 [_memoryCache setObject:image forKey:key withCost:[_self imageCost:image]]; } else { //否则开启一个异步的解码队列,把图片转成位图,再丢进缓存里面 dispatch_async(YYImageCacheDecodeQueue(), ^{ __strong typeof(_self) self = _self; if (!self) return; [self.memoryCache setObject:[image yy_imageByDecoded] forKey:key withCost:[self imageCost:image]]; }); } } else if (imageData) {//如果图片不存在,图片数据存在,那就通过data生成一个图片,丢进内存中存起来 dispatch_async(YYImageCacheDecodeQueue(), ^{ __strong typeof(_self) self = _self; if (!self) return; UIImage *newImage = [self imageFromData:imageData]; [self.memoryCache setObject:[self imageFromData:imageData] forKey:key withCost:[self imageCost:newImage]]; }); } } //如果类型包含磁盘缓存,存进磁盘 if (type & YYImageCacheTypeDisk) { // add to disk cache if (imageData) { if (image) { [YYDiskCache setExtendedData:[NSKeyedArchiver archivedDataWithRootObject:@(image.scale)] toObject:imageData]; } [_diskCache setObject:imageData forKey:key]; } else if (image) { dispatch_async(YYImageCacheIOQueue(), ^{ __strong typeof(_self) self = _self; if (!self) return; NSData *data = [image yy_imageDataRepresentation]; [YYDiskCache setExtendedData:[NSKeyedArchiver archivedDataWithRootObject:@(image.scale)] toObject:data]; [self.diskCache setObject:data forKey:key]; }); } }}/** * 全删咯 * */- (void)removeImageForKey:(NSString *)key { [self removeImageForKey:key withType:YYImageCacheTypeAll];}//有哪个类型删哪个- (void)removeImageForKey:(NSString *)key withType:(YYImageCacheType)type { if (type & YYImageCacheTypeMemory) [_memoryCache removeObjectForKey:key]; if (type & YYImageCacheTypeDisk) [_diskCache removeObjectForKey:key];}- (BOOL)containsImageForKey:(NSString *)key { return [self containsImageForKey:key withType:YYImageCacheTypeAll];}- (BOOL)containsImageForKey:(NSString *)key withType:(YYImageCacheType)type { if (type & YYImageCacheTypeMemory) { if ([_memoryCache containsObjectForKey:key]) return YES; } if (type & YYImageCacheTypeDisk) { if ([_diskCache containsObjectForKey:key]) return YES; } return NO;}- (UIImage *)getImageForKey:(NSString *)key { return [self getImageForKey:key withType:YYImageCacheTypeAll];}//通过key找图片,都比较简单- (UIImage *)getImageForKey:(NSString *)key withType:(YYImageCacheType)type { if (!key) return nil; if (type & YYImageCacheTypeMemory) { UIImage *image = [_memoryCache objectForKey:key]; if (image) return image; } if (type & YYImageCacheTypeDisk) { NSData *data = (id)[_diskCache objectForKey:key]; UIImage *image = [self imageFromData:data]; if (image && (type & YYImageCacheTypeMemory)) { [_memoryCache setObject:image forKey:key withCost:[self imageCost:image]]; } return image; } return nil;}//跟上个方法类似,只不过把查询的结果通过block传递了回去- (void)getImageForKey:(NSString *)key withType:(YYImageCacheType)type withBlock:(void (^)(UIImage *image, YYImageCacheType type))block { if (!block) return; dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0), ^{ UIImage *image = nil; if (type & YYImageCacheTypeMemory) { image = [_memoryCache objectForKey:key]; if (image) { dispatch_async(dispatch_get_main_queue(), ^{ block(image, YYImageCacheTypeMemory); }); return; } } if (type & YYImageCacheTypeDisk) { NSData *data = (id)[_diskCache objectForKey:key]; image = [self imageFromData:data]; if (image) { [_memoryCache setObject:image forKey:key]; dispatch_async(dispatch_get_main_queue(), ^{ block(image, YYImageCacheTypeDisk); }); return; } } dispatch_async(dispatch_get_main_queue(), ^{ block(nil, YYImageCacheTypeNone); }); });}- (NSData *)getImageDataForKey:(NSString *)key { return (id)[_diskCache objectForKey:key];}- (void)getImageDataForKey:(NSString *)key withBlock:(void (^)(NSData *imageData))block { if (!block) return; dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0), ^{ NSData *data = (id)[_diskCache objectForKey:key]; dispatch_async(dispatch_get_main_queue(), ^{ block(data); }); });}@end联系客服
