SDWebImage前世今生之V2.4版本

2.4版本2011年10月1日发布

1. 类结构新增了两个类

• UIButton+WebCache 设置Button Image

//------------------------------2.4版本更新-功能扩展-------------------------
@interface UIButton (WebCache) 

- (void)setImageWithURL:(NSURL *)url;
- (void)setImageWithURL:(NSURL *)url placeholderImage:(UIImage *)placeholder;
- (void)cancelCurrentImageLoad;

@end
//-----------------------------------end-----------------------------------

//------------------------------2.4版本更新-功能优化-------------------------
@implementation UIButton (WebCache)

- (void)setImageWithURL:(NSURL *)url{
    [self setImageWithURL:url placeholderImage:nil];
}

- (void)setImageWithURL:(NSURL *)url placeholderImage:(UIImage *)placeholder{
    SDWebImageManager *manager = [SDWebImageManager sharedManager];
    //从队列中删除正在进行中的下载加载程序
    [manager cancelForDelegate:self];
    [self setImage:placeholder forState:UIControlStateNormal];
    if (url){
        [manager downloadWithURL:url delegate:self];
    }
}

- (void)cancelCurrentImageLoad{
    [[SDWebImageManager sharedManager] cancelForDelegate:self];
}

- (void)webImageManager:(SDWebImageManager *)imageManager didFinishWithImage:(UIImage *)image{
    //下载成功
    //正常情况下Button图片（默认情况下）：UIControlStateNormal
    [self setImage:image forState:UIControlStateNormal];
}

@end
//-----------------------------------end-----------------------------------

• SDWebImageCompat.h 系统版本兼容（设备、平台兼容）

#import 

//-------------------2.4版本更新-新增平台兼容-------------------
//TARGET_OS_IPHONE  //真机
//TARGET_IPHONE_SIMULATOR  //模拟器
#if !TARGET_OS_IPHONE
#import 

#ifndef UIImage
#define UIImage NSImage
#endif

#ifndef UIImageView
#define UIImageView NSImageView
#endif
#else
#import 
#endif
//----------------------------end----------------------------

2. SDWebImageManager

• 重命名下载器代理对象集合（downloadDelegates）
• 新增缓存器代理对象集合
• 新增重新下载功能（下载失败了）

@interface SDWebImageManager : NSObject {
    NSMutableArray *downloaders;
    NSMutableDictionary *downloaderForURL;
    NSMutableArray *failedURLs;
    
    //-----------------------2.4版本更新-下载回调与缓存回调-----------------------
    //存储下载器代理对象（下载多张图片，存在多个代理）
    NSMutableArray *downloadDelegates;
    //存储缓存器代理对象（缓存多张图片，存在多个代理）
    NSMutableArray *cacheDelegates;
    //------------------------------------end---------------------------------
}

//-----------------------2.4版本更新-新增-重新下载方法 、低优先级回调-----------------------
- (void)downloadWithURL:(NSURL *)url delegate:(id)delegate retryFailed:(BOOL)retryFailed;
- (void)downloadWithURL:(NSURL *)url delegate:(id)delegate retryFailed:(BOOL)retryFailed lowPriority:(BOOL)lowPriority;
//------------------------------------end---------------------------------
@end

3. SDWebImageManagerDelegate

• 新增didFailWithError回调

@protocol SDWebImageManagerDelegate 
@optional
- (void)webImageManager:(SDWebImageManager *)imageManager didFinishWithImage:(UIImage *)image;

//-----------------------2.4版本更新-错误回调-----------------------
- (void)webImageManager:(SDWebImageManager *)imageManager didFailWithError:(NSError *)error;
//---------------------------------end------------------------------
@end

4. SDWebImageDownloader

• 新增下载器通知（通知的方式回调）
  开始下载：SDWebImageDownloadStartNotification
  结束下载：SDWebImageDownloadStopNotification
• 增加用户信息属性与下载优先级
  用户信息属性：userInfo（保存一些公共参数信息）
  下载优先级：lowPriority（是否重新下载）
• 新增两个方法重载
  用户信息：
  + (id)downloaderWithURL:(NSURL *)url delegate:(id)delegate userInfo:(id)userInfo;
  下载优先级：
  + (id)downloaderWithURL:(NSURL *)url delegate:(id)delegate userInfo:(id)userInfo lowPriority:(BOOL)lowPriority;

//-----------------------2.4版本更新-功能优化-----------------------
extern NSString *const SDWebImageDownloadStartNotification;
extern NSString *const SDWebImageDownloadStopNotification;
//-----------------------------end-------------------------------

@interface SDWebImageDownloader : NSObject{
    @private
    NSURL *url;
    NSURLConnection *connection;
    NSMutableData *imageData;
    //-----------------------2.4版本更新-功能优化-----------------------
    id userInfo;
    BOOL lowPriority;
    //-----------------------------end-------------------------------
}
@property (nonatomic, retain) NSURL *url;
@property (nonatomic, assign) id delegate;

@property (nonatomic, retain) NSMutableData *imageData;

//-----------------------2.4版本更新-功能优化--------------
@property (nonatomic, retain) id userInfo;
@property (nonatomic, readwrite) BOOL lowPriority;
//-----------------------------end----------------------

+ (id)downloaderWithURL:(NSURL *)url delegate:(id)delegate;

//-----------------------2.4版本更新-新增功能--------------
+ (id)downloaderWithURL:(NSURL *)url delegate:(id)delegate userInfo:(id)userInfo lowPriority:(BOOL)lowPriority;
+ (id)downloaderWithURL:(NSURL *)url delegate:(id)delegate userInfo:(id)userInfo;
//-----------------------------end----------------------
@end

//-----------------------2.4版本更新-功能优化-----------------------
NSString *const SDWebImageDownloadStartNotification = @"SDWebImageDownloadStartNotification";
NSString *const SDWebImageDownloadStopNotification = @"SDWebImageDownloadStopNotification";
//-----------------------------end-------------------------------

@implementation SDWebImageDownloader

//-----------------------------------2.4版本更新-新增功能----------------------------
+ (id)downloaderWithURL:(NSURL *)url delegate:(id)delegate{
    return [self downloaderWithURL:url delegate:delegate userInfo:nil];
}
+ (id)downloaderWithURL:(NSURL *)url delegate:(id)delegate userInfo:(id)userInfo{
    return [self downloaderWithURL:url delegate:delegate userInfo:userInfo lowPriority:NO];
}

+ (id)downloaderWithURL:(NSURL *)url delegate:(id)delegate userInfo:(id)userInfo lowPriority:(BOOL)lowPriority{
    //绑定SDNetworkActivityIndicator(下载地址:http://github.com/rs/SDNetworkActivityIndicator)
    //要使用它，除了SDWebImage的导入，只需添加#import "SDNetworkActivityIndicator
    if (NSClassFromString(@"SDNetworkActivityIndicator")){
        id activityIndicator = [NSClassFromString(@"SDNetworkActivityIndicator") performSelector:NSSelectorFromString(@"sharedActivityIndicator")];
        [[NSNotificationCenter defaultCenter] addObserver:activityIndicator
                                                 selector:NSSelectorFromString(@"startActivity")
                                                     name:SDWebImageDownloadStartNotification object:nil];
        [[NSNotificationCenter defaultCenter] addObserver:activityIndicator
                                                 selector:NSSelectorFromString(@"stopActivity")
                                                     name:SDWebImageDownloadStopNotification object:nil];
    }

    SDWebImageDownloader *downloader = [[SDWebImageDownloader alloc] init];
    downloader.url = url;
    downloader.delegate = delegate;
    downloader.userInfo = userInfo;
    downloader.lowPriority = lowPriority;
    [downloader performSelectorOnMainThread:@selector(start) withObject:nil waitUntilDone:YES];
    return downloader;
}
//-----------------------------------------end------------------------------------

- (void)start{
    //------------------------------2.4版本更新-功能优化-------------------------
    //为了防止潜在的重复缓存(NSURLCache + SDImageCache)，我们为图像请求禁用缓存
    NSURLRequest *request = [[NSURLRequest alloc] initWithURL:url cachePolicy:NSURLRequestReloadIgnoringLocalCacheData timeoutInterval:15];
    self.connection = [[NSURLConnection alloc] initWithRequest:request delegate:self startImmediately:NO];
    //如果不是低优先级模式，确保我们不会被UI操作阻塞(NSURLConnection的默认runloop模式是NSEventTrackingRunLoopMode)
    if (!lowPriority){
        [connection scheduleInRunLoop:[NSRunLoop currentRunLoop] forMode:NSRunLoopCommonModes];
    }
    [connection start];
    if (connection){
        self.imageData = [NSMutableData data];
        [[NSNotificationCenter defaultCenter] postNotificationName:SDWebImageDownloadStartNotification object:nil];
    } else {
        if ([delegate respondsToSelector:@selector(imageDownloader:didFailWithError:)]){
            [delegate performSelector:@selector(imageDownloader:didFailWithError:) withObject:self withObject:nil];
        }
    }
    //--------------------------------------end-------------------------------
}

//------------------------------2.4版本更新-功能优化-------------------------
#pragma GCC diagnostic ignored "-Wundeclared-selector"
//-----------------------------------end-----------------------------------
- (void)connectionDidFinishLoading:(NSURLConnection *)aConnection{
    self.connection = nil;
    //------------------------------2.4版本更新-功能优化-------------------------
    [[NSNotificationCenter defaultCenter] postNotificationName:SDWebImageDownloadStopNotification object:nil];
    //-----------------------------------end-----------------------------------
    if ([delegate respondsToSelector:@selector(imageDownloaderDidFinish:)]){
        [delegate performSelector:@selector(imageDownloaderDidFinish:) withObject:self];
    }
    if ([delegate respondsToSelector:@selector(imageDownloader:didFinishWithImage:)]){
        UIImage *image = [[UIImage alloc] initWithData:imageData];
        [delegate performSelector:@selector(imageDownloader:didFinishWithImage:) withObject:self withObject:image];
    }
}
- (void)connection:(NSURLConnection *)connection didFailWithError:(NSError *)error{
    //------------------------------2.4版本更新-功能优化-------------------------
    [[NSNotificationCenter defaultCenter] postNotificationName:SDWebImageDownloadStopNotification object:nil];
    //-----------------------------------end-----------------------------------
    if ([delegate respondsToSelector:@selector(imageDownloader:didFailWithError:)]){
        [delegate performSelector:@selector(imageDownloader:didFailWithError:) withObject:self withObject:error];
    }
    self.connection = nil;
    self.imageData = nil;
}

//------------------------------2.4版本更新-功能优化-------------------------
- (void)dealloc{
    [[NSNotificationCenter defaultCenter] removeObserver:self];
}
//-----------------------------------end----------------------------------


@end

5. SDImageCache

• 新增系统平台兼容iPhone系统TARGET_OS_IPHONE

//-----------------------2.4版本更新-系统版本兼容-----------------------
        #if TARGET_OS_IPHONE
        //--------------------------------end--------------------------------
        //订阅应用程序事件
        //应用程序终止，里面回调didReceiveMemoryWarning方法，清空内存
        [[NSNotificationCenter defaultCenter] addObserver:self
                                                 selector:@selector(clearMemory)
                                        name:UIApplicationDidReceiveMemoryWarningNotification
                                                   object:nil];
        //应用程序终止，里面回调willTerminate方法，清空磁盘
        [[NSNotificationCenter defaultCenter] addObserver:self
                                                 selector:@selector(cleanDisk)
                                                name:UIApplicationWillTerminateNotification
                                                   object:nil];

        //-----------------------2.1版本更新-系统版本兼容-----------------------
        #ifdef __IPHONE_4_0
       
        UIDevice *device = [UIDevice currentDevice];
        if ([device respondsToSelector:@selector(isMultitaskingSupported)] && device.multitaskingSupported){
            [[NSNotificationCenter defaultCenter] addObserver:self
                                                     selector:@selector(clearMemory)
                                                         name:UIApplicationDidEnterBackgroundNotification
                                                       object:nil];
        }
       
        #endif
        //--------------------------------end--------------------------------
        #endif

• 将图片数据缓存磁盘支持了TARGET_OS_IPHONE

- (void)storeKeyWithDataToDisk:(NSArray *)keyAndData{
    NSFileManager *fileManager = [[NSFileManager alloc] init];
    NSString *key = [keyAndData objectAtIndex:0];
    NSData *data = [keyAndData count] > 1 ? [keyAndData objectAtIndex:1] : nil;
    if (data){
        [fileManager createFileAtPath:[self cachePathForKey:key] contents:data attributes:nil];
    } else {
        //如果没有给定的数据表示，转换JPEG中的UIImage并存储它
        //这个技巧占用更多的CPU/内存，并且不保留alpha通道
        //线程安全，没有锁
        UIImage *image = [self imageFromKey:key fromDisk:YES];
        if (image){
            //-----------------------2.4版本更新-系统版本兼容-----------------------
            #if TARGET_OS_IPHONE
            [fileManager createFileAtPath:[self cachePathForKey:key] contents:UIImageJPEGRepresentation(image, (CGFloat)1.0) attributes:nil];
            #else
            NSArray* representations  = [image representations];
            NSData* jpegData = [NSBitmapImageRep representationOfImageRepsInArray: representations usingType: NSJPEGFileType properties:nil];
            [fileManager createFileAtPath:[self cachePathForKey:key] contents:jpegData attributes:nil];
            #endif
            //--------------------------------end--------------------------------
        }
    }
}

• 图片缓存优化

- (void)storeImage:(UIImage *)image imageData:(NSData *)data forKey:(NSString *)key toDisk:(BOOL)toDisk{
    //-----------------------2.4版本更新-功能优化-----------------------
    if (!image || !key){
        return;
    }
    [memCache setObject:image forKey:key];
    if (toDisk){
        if (!data)
            return;
        NSArray *keyWithData;
        if (data){
            keyWithData = [NSArray arrayWithObjects:key, data, nil];
        }else{
            keyWithData = [NSArray arrayWithObjects:key, nil];
        }
        [cacheInQueue addOperation:[[NSInvocationOperation alloc] initWithTarget:self
 selector:@selector(storeKeyWithDataToDisk:) object:keyWithData]];
    }
    //------------------------------end------------------------------
}