1、ImageCache
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使用内存缓存方式：
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使用沙盒缓存方式：
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使用网络图片第三方库方式：
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SDWebImage：
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iOS 中著名的网络图片处理框架
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包含的功能：图片下载、图片缓存、下载进度监听、gif 处理等等
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用法极其简单，功能十分强大，大大提高了网络图片的处理效率
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国内超过 90% 的 iOS 项目都有它的影子
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1、图片文件缓存的时间有多长？
- 1 周
_maxCacheAge = kDefaultCacheMaxCacheAge; // - (id)initWithNamespace: diskCacheDirectory: static const NSInteger kDefaultCacheMaxCacheAge = 60 * 60 * 24 * 7; // 1 week SDImageCache.m -
2、SDWebImage 的内存缓存是用什么实现的？
- NSCache
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3、SDWebImage 的最大并发数是多少？
- 是程序固定死了，可以通过属性进行调整！
_downloadQueue.maxConcurrentOperationCount = 6; // SDWebImageDownloader.m - (id)init -
4、网络访问超时时长
- iOS 开发中，默认的访问时长是 1 分钟，SDWebImage 中是 15 秒。
_downloadTimeout = 15.0; // SDWebImageDownloader.m - (id)init -
5、SDWebImage 支持动图吗？GIF
- 支持
#import <ImageIO/ImageIO.h> // UIImage+GIF.m [UIImage animatedImageWithImages:images duration:duration]; -
6、SDWebImage 是如何区分不同格式的图像的
- 根据图像数据第一个字节来判断的！
// NSData+ImageContentType.m + (NSString *)sd_contentTypeForImageData: PNG：0x89 image/png ，压缩比没有 JPG 高，但是无损压缩，解压缩性能高，苹果推荐的图像格式！ JPG：0xFF image/jpeg，压缩比最高的一种图片格式，有损压缩！最多使用的场景，照相机！解压缩的性能不好！ GIF：0x47 image/gif ，序列桢动图，特点：只支持 256 种颜色！最流行的时候在 1998～1999，有专利的！ -
7、SDWebImage 缓存图片的名称是怎么确定的！
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md5
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如果单纯使用 文件名保存，重名的几率很高！
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使用 MD5 的散列函数！对完整的 URL 进行 md5，结果是一个 32 个字符长度的字符串！
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8、SDWebImage 的内存警告是如何处理的！
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利用通知中心观察
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UIApplicationDidReceiveMemoryWarningNotification 接收到内存警告的通知
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执行 clearMemory 方法，清理内存缓存！
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UIApplicationWillTerminateNotification 接收到应用程序将要终止通知
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执行 cleanDisk 方法，清理磁盘缓存！
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UIApplicationDidEnterBackgroundNotification 接收到应用程序进入后台通知
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执行 backgroundCleanDisk 方法，后台清理磁盘！
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通过以上通知监听，能够保证缓存文件的大小始终在控制范围之内！
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clearDisk 清空磁盘缓存，将所有缓存目录中的文件，全部删除！ 实际工作，将缓存目录直接删除，再次创建一个同名空目录！
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bug:
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SDWebImage 中，一旦内存警告，清理了内存之后，之后所有的图片都是从沙盒加载的。
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原因：NSCache 中一旦调用了 removeAllObjects，就无法给 cache 添加对象。关于 NSCache 的内存管理，交给他自己就行！
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2、自定义内存缓存方式
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Objective-C
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AppInfoModel.h
@interface AppInfoModel : NSObject /// 标题名称 @property (nonatomic, strong) NSString *name; /// 下载数量 @property (nonatomic, strong) NSString *download; /// 图片地址 @property (nonatomic, strong) NSString *icon; /// 声明工厂方法，数据源初始化方法 + (instancetype)appInfoModelWithDict:(NSDictionary *)dict; @end -
AppInfoModel.m
// 实现工厂方法 + (instancetype)appInfoModelWithDict:(NSDictionary *)dict { id obj = [[self alloc] init]; [obj setValuesForKeysWithDictionary:dict]; return obj; } -
AppInfoCell.h
@interface AppInfoCell : UITableViewCell @property (nonatomic, weak) IBOutlet UILabel *nameLabel; @property (nonatomic, weak) IBOutlet UILabel *downloadLabel; @property (nonatomic, weak) IBOutlet UIImageView *iconImageView; @end -
ViewController.m
/// 表格数据源 @property (nonatomic, strong) NSArray *dataSourceArray; /// 图片下载队列 @property (nonatomic, strong) NSOperationQueue *downloadQueue; /// 下载缓冲池 @property (nonatomic, strong) NSMutableDictionary *downloadQueueCache; /// 图片缓冲池 @property (nonatomic, strong) NSMutableDictionary *imageCache; /// 图片下载地址黑名单 @property (nonatomic, retain) NSMutableArray *urlBlackList; // 懒加载 - (NSArray *)dataSourceArray { if (_dataSourceArray == nil) { NSArray *array = [NSArray arrayWithContentsOfURL:[[NSBundle mainBundle] URLForResource:@"apps.plist" withExtension:nil]]; NSMutableArray *arrayM = [NSMutableArray arrayWithCapacity:array.count]; [array enumerateObjectsUsingBlock:^(id obj, NSUInteger idx, BOOL *stop) { [arrayM addObject:[AppInfoModel appInfoModelWithDict:obj]]; }]; _dataSourceArray = [arrayM copy]; } return _dataSourceArray; } - (NSOperationQueue *)downloadQueue { if (_downloadQueue == nil) { _downloadQueue = [[NSOperationQueue alloc] init]; } return _downloadQueue; } - (NSMutableDictionary *)downloadQueueCache { if (_downloadQueueCache == nil) { _downloadQueueCache = [[NSMutableDictionary alloc] init]; } return _downloadQueueCache; } - (NSMutableDictionary *)imageCache { if (_imageCache == nil) { _imageCache = [[NSMutableDictionary alloc] init]; } return _imageCache; } - (NSMutableArray *)urlBlackList { if (_urlBlackList == nil) { _urlBlackList = [[NSMutableArray alloc] init]; } return _urlBlackList; } // 表格视图数据源方法 - (NSInteger)tableView:(UITableView *)tableView numberOfRowsInSection:(NSInteger)section { return self.dataSourceArray.count; } - (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath { AppInfoCell *cell = [tableView dequeueReusableCellWithIdentifier:@"AppCell" forIndexPath:indexPath]; AppInfoModel *dataModel = self.dataSourceArray[indexPath.row]; cell.nameLabel.text = dataModel.name; cell.downloadLabel.text = dataModel.download; // 判断图片缓存池中是否有相应的图片 if (self.imageCache[dataModel.icon] != nil) { // 从缓存池中取出图片显示在 Cell 上 cell.iconImageView.image = self.imageCache[dataModel.icon]; } else { // 从网络异步下载图片 [self downloadImageWithIndexPath:indexPath]; } return cell; } - (void)downloadImageWithIndexPath:(NSIndexPath *)indexPath { AppInfoModel *dataModel = self.dataSourceArray[indexPath.row]; // 判断下载缓冲池中是否存在当前下载操作 if (self.downloadQueueCache[dataModel.icon] != nil) { return; } // 判断图片地址是否在黑名单中 if ([self.urlBlackList containsObject:dataModel.icon]) { return; } // 创建异步下载图片操作 NSBlockOperation *downloadOperation = [NSBlockOperation blockOperationWithBlock:^{ UIImage *image = [UIImage imageWithData:[NSData dataWithContentsOfURL:[NSURL URLWithString:dataModel.icon]]]; // 下载完成从下载缓冲池中删除当前下载操作 [self.downloadQueueCache removeObjectForKey:dataModel.icon]; // 添加黑名单记录 if (image == nil && ![self.urlBlackList containsObject:dataModel.icon]) { [self.urlBlackList addObject:dataModel.icon]; } // 主线程跟新 UI [[NSOperationQueue mainQueue] addOperationWithBlock:^{ if (image != nil) { // 将下载完成的图片保存到图片缓冲池中 [self.imageCache setObject:image forKey:dataModel.icon]; [self.tableView reloadRowsAtIndexPaths:@[indexPath] withRowAnimation:UITableViewRowAnimationAutomatic]; } }]; }]; // 将当前下载添加到下载缓冲池中 [self.downloadQueueCache setObject:downloadOperation forKey:dataModel.icon]; // 开始异步下载图片 [self.downloadQueue addOperation:downloadOperation]; } // 内存警告 /* 日常上课通常就直接删除，但是在工作后，必须要处理！不处理后果很严重，第一次内存警告如果不处理，就没有第二次的机会了，就直接被闪退了 */ - (void)didReceiveMemoryWarning { [super didReceiveMemoryWarning]; // 清理缓冲池 [self.downloadQueueCache removeAllObjects]; [self.imageCache removeAllObjects]; // 取消下载操作，等用户再滚动表格，调用数据源方法，又能够自动下载 [self.downloadQueue cancelAllOperations]; }
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Swift
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AppInfo.swift
class AppInfo: NSObject { var name:String! var icon:String! var download:String! class func AppInfoWithDict(dict:[String:AnyObject]) -> AnyObject { let obj:AnyObject = self.init() obj.setValuesForKeysWithDictionary(dict) return obj } required override init() { super.init() } } -
AppInfoCell.swift
class AppInfoCell: UITableViewCell { @IBOutlet weak var iconView: UIImageView! @IBOutlet weak var nameLabel: UILabel! @IBOutlet weak var downLabel: UILabel! } -
ViewController.swift
// 懒加载 // 数据源 lazy var dataSourceArray:[AnyObject] = { var dataArray:[AnyObject] = Array() let array = NSArray(contentsOfURL: NSBundle.mainBundle().URLForResource("apps.plist", withExtension: nil)!) array!.enumerateObjectsUsingBlock { (obj:AnyObject, idx:Int, stop:UnsafeMutablePointer<ObjCBool>) in dataArray.append(AppInfoModel.AppInfoWithDict(obj as! [String : AnyObject])) } return dataArray }() // 下载队列 lazy var downloadQueue:NSOperationQueue = { var tmp:NSOperationQueue = NSOperationQueue() return tmp }() // 下载缓冲池 lazy var downloadQueueCache:[String:NSBlockOperation] = { var tmp:[String:NSBlockOperation] = Dictionary() return tmp }() // 图片缓冲池 lazy var imageCache:[String:UIImage] = { var tmp:[String:UIImage] = Dictionary() return tmp }() // 图片下载地址黑名单 lazy var urlBlackList:[String] = { var tmp:[String] = Array() return tmp }() // 表格视图数据源方法 override func tableView(tableView: UITableView, numberOfRowsInSection section: Int) -> Int { return self.dataSourceArray.count } override func tableView(tableView: UITableView, cellForRowAtIndexPath indexPath: NSIndexPath) -> UITableViewCell { let cell:AppInfoCell = tableView.dequeueReusableCellWithIdentifier("AppCell", forIndexPath: indexPath) as! AppInfoCell let dataModel = self.dataSourceArray[indexPath.row] as! AppInfoModel cell.nameLabel.text = dataModel.name cell.downLabel.text = dataModel.download // 判断图片缓存池中是否有相应的图片 if self.imageCache[dataModel.icon] != nil { // 从缓存池中取出图片显示在 Cell 上 cell.iconView.image = self.imageCache[dataModel.icon] } else { // 从网络异步下载图片 self.downloadImageWithIndexPath(indexPath) } return cell } func downloadImageWithIndexPath(indexPath:NSIndexPath) { let dataModel = self.dataSourceArray[indexPath.row] as! AppInfoModel // 判断下载缓冲池中是否存在当前下载操作 if self.downloadQueueCache[dataModel.icon] != nil { return } // 判断图片地址是否在黑名单中 if self.urlBlackList.contains(dataModel.icon) { return } // 创建异步下载图片操作 let downloadOperation = NSBlockOperation { let image:UIImage? = UIImage(data: NSData(contentsOfURL: NSURL(string: dataModel.icon)!)!) // 下载完成从下载缓冲池中删除当前下载操作 self.downloadQueueCache.removeValueForKey(dataModel.icon) // 添加黑名单记录 if image == nil && !self.urlBlackList.contains(dataModel.icon) { self.urlBlackList.append(dataModel.icon) } // 主线程跟新 UI NSOperationQueue.mainQueue().addOperationWithBlock({ if image != nil { // 将下载完成的图片保存到图片缓冲池中 self.imageCache[dataModel.icon] = image self.tableView.reloadRowsAtIndexPaths([indexPath], withRowAnimation: .Automatic) } }) } // 将当前下载添加到下载缓冲池中 self.downloadQueueCache[dataModel.icon] = downloadOperation // 开始异步下载图片 self.downloadQueue.addOperation(downloadOperation) } // 内存警告 override func didReceiveMemoryWarning() { super.didReceiveMemoryWarning() self.downloadQueueCache.removeAll() self.imageCache.removeAll() self.downloadQueue.cancelAllOperations() }
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3、自定义沙盒缓存方式
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Objective-C
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AppInfoModel.h
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AppInfoModel.m
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AppInfoCell.h
- 与上边一样
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NSString+BundlePath.h
/// 拼接缓存目录 - (NSString *)appendCachePath; -
NSString+BundlePath.m
- (NSString *)appendCachePath { NSString *dir = NSSearchPathForDirectoriesInDomains(NSCachesDirectory, NSUserDomainMask, YES).lastObject; return [dir stringByAppendingPathComponent:self.lastPathComponent]; } -
ViewController.m
// 懒加载 与上边一样 // 表格视图数据源方法 - (NSInteger)tableView:(UITableView *)tableView numberOfRowsInSection:(NSInteger)section { return self.dataSourceArray.count; } - (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath { AppInfoCell *cell = [tableView dequeueReusableCellWithIdentifier:@"AppCell" forIndexPath:indexPath]; AppInfoModel *dataModel = self.dataSourceArray[indexPath.row]; cell.nameLabel.text = dataModel.name; cell.downloadLabel.text = dataModel.download; // 判断图片缓存池中是否有相应的图片 if (self.imageCache[dataModel.icon] != nil) { // 从缓存池中取出图片显示在 Cell 上 cell.iconImageView.image = self.imageCache[dataModel.icon]; } else { // 从沙盒加载图片 UIImage *image = [UIImage imageWithContentsOfFile:[dataModel.icon appendCachePath]]; if (image != nil) { cell.iconImageView.image = image; self.imageCache[dataModel.icon] = image; } else { // 从网络异步下载图片 [self downloadImageWithIndexPath:indexPath]; } } return cell; } - (void)downloadImageWithIndexPath:(NSIndexPath *)indexPath { AppInfoModel *dataModel = self.dataSourceArray[indexPath.row]; // 判断下载缓冲池中是否存在当前下载操作 if (self.downloadQueueCache[dataModel.icon] != nil) { return; } // 判断图片地址是否在黑名单中 if ([self.urlBlackList containsObject:dataModel.icon]) { return; } // 创建异步下载图片操作 NSBlockOperation *downloadOperation = [NSBlockOperation blockOperationWithBlock:^{ NSData *imageData = [NSData dataWithContentsOfURL:[NSURL URLWithString:dataModel.icon]]; UIImage *image = [UIImage imageWithData:imageData]; // 下载完成从下载缓冲池中删除当前下载操作 [self.downloadQueueCache removeObjectForKey:dataModel.icon]; // 添加黑名单记录 if (image == nil && ![self.urlBlackList containsObject:dataModel.icon]) { [self.urlBlackList addObject:dataModel.icon]; } if (image != nil) { // 将图像写入沙盒 [imageData writeToFile:[dataModel.icon appendCachePath] atomically:YES]; } // 主线程跟新 UI [[NSOperationQueue mainQueue] addOperationWithBlock:^{ if (image != nil) { // 将下载完成的图片保存到图片缓冲池中 [self.imageCache setObject:image forKey:dataModel.icon]; [self.tableView reloadRowsAtIndexPaths:@[indexPath] withRowAnimation:UITableViewRowAnimationAutomatic]; } }]; }]; // 将当前下载添加到下载缓冲池中 [self.downloadQueueCache setObject:downloadOperation forKey:dataModel.icon]; // 开始异步下载图片 [self.downloadQueue addOperation:downloadOperation]; } // 内存警告 与上边一样
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Swift
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AppInfo.swift
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AppInfoCell.swift
- 与上边一样
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String+BundlePath.swift
public func appendCachePath() -> String? { let dir:String? = NSSearchPathForDirectoriesInDomains(.CachesDirectory, .UserDomainMask, true).last if (dir != nil) { return dir! + "/" + (self as NSString).lastPathComponent } else { return nil } } -
ViewController.swift
// 懒加载 与上边一样 // 表格视图数据源方法 override func tableView(tableView: UITableView, numberOfRowsInSection section: Int) -> Int { return self.dataSourceArray.count } override func tableView(tableView: UITableView, cellForRowAtIndexPath indexPath: NSIndexPath) -> UITableViewCell { let cell:AppInfoCell = tableView.dequeueReusableCellWithIdentifier("AppCell", forIndexPath: indexPath) as! AppInfoCell let dataModel = self.dataSourceArray[indexPath.row] as! AppInfoModel cell.nameLabel.text = dataModel.name cell.downLabel.text = dataModel.download // 判断图片缓存池中是否有相应的图片 if self.imageCache[dataModel.icon] != nil { // 从缓存池中取出图片显示在 Cell 上 cell.iconView.image = self.imageCache[dataModel.icon] } else { // 从沙盒加载图片 let image = UIImage(contentsOfFile: dataModel.icon.appendCachePath()!) if (image != nil) { cell.iconView.image = image self.imageCache[dataModel.icon] = image } else { // 从网络异步下载图片 self.downloadImageWithIndexPath(indexPath) } } return cell } func downloadImageWithIndexPath(indexPath:NSIndexPath) { let dataModel = self.dataSourceArray[indexPath.row] as! AppInfoModel // 判断下载缓冲池中是否存在当前下载操作 if self.downloadQueueCache[dataModel.icon] != nil { return } // 判断图片地址是否在黑名单中 if self.urlBlackList.contains(dataModel.icon) { return } // 创建异步下载图片操作 let downloadOperation = NSBlockOperation { let imageData:NSData? = NSData(contentsOfURL: NSURL(string: dataModel.icon)!) let image:UIImage? = UIImage(data: imageData!) // 下载完成从下载缓冲池中删除当前下载操作 self.downloadQueueCache.removeValueForKey(dataModel.icon) // 添加黑名单记录 if image == nil && !self.urlBlackList.contains(dataModel.icon) { self.urlBlackList.append(dataModel.icon) } if image != nil { // 将图像写入沙盒 imageData!.writeToFile(dataModel.icon.appendCachePath()!, atomically: true) print(dataModel.icon.appendCachePath()!) } // 主线程跟新 UI NSOperationQueue.mainQueue().addOperationWithBlock({ if image != nil { // 将下载完成的图片保存到图片缓冲池中 self.imageCache[dataModel.icon] = image self.tableView.reloadRowsAtIndexPaths([indexPath], withRowAnimation: .Automatic) } }) } // 将当前下载添加到下载缓冲池中 self.downloadQueueCache[dataModel.icon] = downloadOperation // 开始异步下载图片 self.downloadQueue.addOperation(downloadOperation) } // 内存警告 与上边一样
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4、仿 SDWebImage 缓存方式
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Objective-C
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AppInfoModel.h
@interface AppInfoModel : NSObject /// 标题名称 @property (nonatomic, strong) NSString *name; /// 下载数量 @property (nonatomic, strong) NSString *download; /// 图片地址 @property (nonatomic, strong) NSString *icon; /// 从 Plist 加载 AppInfo + (NSArray *)loadPList; @end -
AppInfoModel.m
+ (NSArray *)loadPList { NSArray *array = [NSArray arrayWithContentsOfURL:[[NSBundle mainBundle] URLForResource:@"apps.plist" withExtension:nil]]; NSMutableArray *plist = [NSMutableArray arrayWithCapacity:array.count]; [array enumerateObjectsUsingBlock:^(id obj, NSUInteger idx, BOOL *stop) { id model = [[self alloc] init]; [model setValuesForKeysWithDictionary:obj]; [plist addObject:model]; }]; return plist; } -
AppInfoCell.h
@interface AppInfoCell : UITableViewCell @property (nonatomic, weak) IBOutlet UILabel *nameLabel; @property (nonatomic, weak) IBOutlet UILabel *downloadLabel; @property (nonatomic, weak) IBOutlet UIImageView *iconImageView; @end -
NSString+BundlePath.h
/// 拼接缓存目录 - (NSString *)appendCachePath; -
NSString+BundlePath.m
- (NSString *)appendCachePath { NSString *dir = NSSearchPathForDirectoriesInDomains(NSCachesDirectory, NSUserDomainMask, YES).lastObject; return [dir stringByAppendingPathComponent:self.lastPathComponent]; } -
WebImageOperation.h
@interface WebImageOperation : NSOperation /// 实例化 web 图像操作 + (instancetype)webImageOperationWithURLString:(NSString *)urlString completion:(void (^)(UIImage *image))completion; @end -
WebImageOperation.m
/// 下载图片的 URL @property (nonatomic, copy) NSString *urlStr; /// 下载完成的回调 @property (nonatomic, copy) void (^completion) (UIImage *image); + (instancetype)webImageOperationWithURLString:(NSString *)urlString completion:(void (^)(UIImage *))completion { WebImageOperation *imageOperation = [[self alloc] init]; imageOperation.urlStr= urlString; imageOperation.completion = completion; return imageOperation; } // 操作加入队列后会自动执行该方法 - (void)main { @autoreleasepool { if (self.isCancelled) return; NSURL *url = [NSURL URLWithString:self.urlStr]; NSData *data = [NSData dataWithContentsOfURL:url]; if (self.isCancelled) return; if (data != nil) { [data writeToFile:self.urlStr.appendCachePath atomically:YES]; } if (self.isCancelled) return; if (self.completion && data != nil) { [[NSOperationQueue mainQueue] addOperationWithBlock:^{ self.completion([UIImage imageWithData:data]); }]; } } } -
WebImageManager.h
// 负责所有网络图像的下载操作以及缓存管理！ @interface WebImageManager : NSObject /// 全局单例访问入口 + (instancetype)sharedManager; /// 下载网络图像 - (void)downloadImage:(NSString *)urlString completion:(void (^) (UIImage *image))completion; /// 取消 urlString 对应的下载操作 - (void)cancelDownload:(NSString *)urlString; @end -
WebImageManager.m
/// 下载队列 @property (nonatomic, strong) NSOperationQueue *downloadQueue; /// 下载操作缓冲池 @property (nonatomic, strong) NSMutableDictionary *downloadQueueCache; /// 图片缓冲池 @property (nonatomic, strong) NSMutableDictionary *imageCache; // 下载管理器 // 实例化下载管理器 + (instancetype)sharedManager { static id instance; static dispatch_once_t onceToken; dispatch_once(&onceToken, ^{ instance = [[self alloc] init]; }); return instance; } // 下载操作 - (void)downloadImage:(NSString *)urlString completion:(void (^)(UIImage *))completion { // 判断缓存中是否存在图像 if ([self checkCacheWithURLString:urlString]) { if (completion != nil) { // 直接回调，传递给调用方图像 completion(self.imageCache[urlString]); } return; } // 判断缓冲池中是否存在下载操作 if (self.downloadQueueCache[urlString] != nil) { return; } WebImageOperation *downloadOperation = [WebImageOperation webImageOperationWithURLString:urlString completion:^(UIImage *image) { // 下载完成从操作缓冲池中移除操作 [self.downloadQueueCache removeObjectForKey:urlString]; // 下载完成添加到图片缓冲池中 [self.imageCache setObject:image forKey:urlString]; if (completion != nil) { completion(image); } }]; // 将操作添加到缓冲池 [self.downloadQueueCache setObject:downloadOperation forKey:urlString]; // 将操作添加到队列 [self.downloadQueue addOperation:downloadOperation]; } // 取消 urlString 对应的下载操作 - (void)cancelDownload:(NSString *)urlString { // 从缓冲池拿到下载操作 WebImageOperation *downloadOperation = self.downloadQueueCache[urlString]; if (downloadOperation != nil) { // 取消操作 [downloadOperation cancel]; // 从缓冲池中删除操作 [self.downloadQueueCache removeObjectForKey:urlString]; } } // 判断缓存中是否存在图像 - (BOOL)checkCacheWithURLString:(NSString *)urlString { // 判断图片缓冲池中是否存在图像 if (self.imageCache[urlString] != nil) { return YES; } UIImage *image = [UIImage imageWithContentsOfFile:[urlString appendCachePath]]; // 判断沙盒中是否存在图像 if (image != nil) { [self.imageCache setObject:image forKey:urlString]; return YES; } return NO; } // 懒加载 - (NSOperationQueue *)downloadQueue { if (_downloadQueue == nil) { _downloadQueue = [[NSOperationQueue alloc] init]; } return _downloadQueue; } - (NSMutableDictionary *)downloadQueueCache { if (_downloadQueueCache == nil) { _downloadQueueCache = [[NSMutableDictionary alloc] init]; } return _downloadQueueCache; } - (NSMutableDictionary *)imageCache { if (_imageCache == nil) { _imageCache = [[NSMutableDictionary alloc] init]; } return _imageCache; } -
UIImageView+WebImageView.h
@interface UIImageView (WebImageView) /// 设置 Web 图像 URL，自动加载图像 - (void)setWebImageWithURL:(NSString *)urlString; @end -
UIImageView+WebImageView.m
#import <objc/runtime.h> // 下载图片的 url @property (nonatomic, copy) NSString *urlStr; - (void)setWebImageWithURL:(NSString *)urlString { // 屏蔽快速滑动重复添加下载 if ([self.urlStr isEqualToString:urlString]) { return; } // 暂停之前的操作 if (self.urlStr != nil && ![self.urlStr isEqualToString:urlString]) { [[WebImageManager sharedManager] cancelDownload:self.urlStr]; // 如果 ImageView 之前有图像-清空图像 self.image = nil; } // 记录新的 url self.urlStr = urlString; __weak typeof(self) weakSelf = self; // 下载网络图片 [[WebImageManager sharedManager] downloadImage:self.urlStr completion:^(UIImage *image) { weakSelf.image = image; }]; } // 向分类添加属性 // 运行时的关联对象，动态添加属性 const void *URLStrKey = "URLStrKey"; - (void)setUrlStr:(NSString *)urlString { objc_setAssociatedObject(self, URLStrKey, urlString, OBJC_ASSOCIATION_COPY_NONATOMIC); } - (NSString *)urlStr { return objc_getAssociatedObject(self, URLStrKey); } -
ViewController.m
/// 表格数据源 @property (nonatomic, strong) NSArray *dataSourceArray; // 懒加载 - (NSArray *)dataSourceArray { if (_dataSourceArray == nil) { _dataSourceArray = [AppInfoModel loadPList]; } return _dataSourceArray; } // 表格视图数据源方法 - (NSInteger)tableView:(UITableView *)tableView numberOfRowsInSection:(NSInteger)section { return self.dataSourceArray.count; } - (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath { AppInfoCell *cell = [tableView dequeueReusableCellWithIdentifier:@"AppCell" forIndexPath:indexPath]; AppInfoModel *dataModel = self.dataSourceArray[indexPath.row]; cell.nameLabel.text = dataModel.name; cell.downloadLabel.text = dataModel.download; [cell.iconImageView setWebImageWithURL:dataModel.icon]; return cell; }
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Swift
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AppInfoModel.swift
class AppInfoModel: NSObject var name:String! var icon:String! var download:String! class func loadPList() -> [AnyObject] { let array = NSArray(contentsOfURL: NSBundle.mainBundle().URLForResource("apps.plist", withExtension: nil)!) var plist:[AnyObject] = Array() array!.enumerateObjectsUsingBlock { (obj:AnyObject, idx:Int, stop:UnsafeMutablePointer<ObjCBool>) in let model:AnyObject = self.init() model.setValuesForKeysWithDictionary(obj as! [String : AnyObject]) plist.append(model) } return plist } class func AppInfoWithDict(dict:[String:AnyObject]) -> AnyObject { let obj:AnyObject = self.init() obj.setValuesForKeysWithDictionary(dict) return obj } required override init() { super.init() } -
AppInfoCell.swift
@IBOutlet weak var iconView: UIImageView! @IBOutlet weak var nameLabel: UILabel! @IBOutlet weak var downLabel: UILabel! -
String+BundlePath.swift
/// 拼接缓存目录 public func appendCachePath() -> String? { let dir:String? = NSSearchPathForDirectoriesInDomains(.CachesDirectory, .UserDomainMask, true).last if (dir != nil) { return dir! + "/" + (self as NSString).lastPathComponent } else { return nil } } -
WebImageOperation.swift
class WebImageOperation: NSOperation /// 下载图片的 URL var urlStr:String! /// 下载完成的回调 var completion:((image:UIImage) -> Void)! class func webImageOperationWithURLString(urlString:String, completion:((image:UIImage) -> Void)) -> WebImageOperation { let imageOperation:WebImageOperation = WebImageOperation() imageOperation.urlStr = urlString imageOperation.completion = completion return imageOperation } // 操作加入队列后会自动执行该方法 override func main() { if self.cancelled == true { return } let url:NSURL = NSURL(string: self.urlStr)! let data:NSData? = NSData(contentsOfURL: url) if self.cancelled == true { return } if data != nil { data?.writeToFile(self.urlStr.appendCachePath()!, atomically: true) } if self.cancelled == true { return } if (self.completion != nil) && (data != nil) { NSOperationQueue.mainQueue().addOperationWithBlock({ self.completion(image: UIImage(data: data!)!) }) } } -
WebImageManager.swift
// 负责所有网络图像的下载操作以及缓存管理！ class WebImageManager: NSObject // 下载队列 lazy var downloadQueue:NSOperationQueue = { var tmp:NSOperationQueue = NSOperationQueue() return tmp }() // 下载缓冲池 lazy var downloadQueueCache:[String:WebImageOperation] = { var tmp:[String:WebImageOperation] = Dictionary() return tmp }() // 图片缓冲池 lazy var imageCache:[String:UIImage] = { var tmp:[String:UIImage] = Dictionary() return tmp }() // 下载管理器 static let sharedManager = WebImageManager() private override init() {} // 下载操作 func downloadImage(urlString:String, completion:((image:UIImage) -> Void)?) { // 判断缓存中是否存在图像 if self.checkCacheWithURLString(urlString) == true { if completion != nil { // 直接回调，传递给调用方图像 completion!(image: self.imageCache[urlString]!) } return } // 判断缓冲池中是否存在下载操作 if self.downloadQueueCache[urlString] != nil { print("玩命下载中...稍安勿躁!") return } let downloadOperation:WebImageOperation = WebImageOperation.webImageOperationWithURLString(urlString) { (image) in // 下载完成从操作缓冲池中移除操作 self.downloadQueueCache.removeValueForKey(urlString) // 下载完成添加到图片缓冲池中 self.imageCache[urlString] = image if (completion != nil) { completion!(image: image); } } // 将操作添加到缓冲池 self.downloadQueueCache[urlString] = downloadOperation // 将操作添加到队列 self.downloadQueue.addOperation(downloadOperation) } // 取消 urlString 对应的下载操作 func cancelDownload(urlString:String) { // 从缓冲池拿到下载操作 let downloadOperation:WebImageOperation? = self.downloadQueueCache[urlString] if downloadOperation != nil { print("取消下载操作") // 取消操作 downloadOperation!.cancel() // 从缓冲池中删除操作 self.downloadQueueCache.removeValueForKey(urlString) } } // 判断缓存中是否存在图像 func checkCacheWithURLString(urlString:String) -> Bool { // 判断图片缓冲池中是否存在图像 if self.imageCache[urlString] != nil { print("从内存中加载...") return true } let image:UIImage? = UIImage(contentsOfFile: urlString.appendCachePath()!) // 判断沙盒中是否存在图像 if image != nil { print("从沙盒中加载...") self.imageCache[urlString] = image return true } return false } -
UIImageView+WebImageView.h
@interface UIImageView (WebImageView) /// 设置 Web 图像 URL，自动加载图像 - (void)setWebImageWithURL:(NSString *)urlString; @end -
UIImageView+WebImageView.m
#import <objc/runtime.h> #import "SwiftImageCache-Swift.h" // 下载图片的 url @property (nonatomic, copy) NSString *urlStr; - (void)setWebImageWithURL:(NSString *)urlString { // 屏蔽快速滑动重复添加下载 if ([self.urlStr isEqualToString:urlString]) { return; } // 暂停之前的操作 if (self.urlStr != nil && ![self.urlStr isEqualToString:urlString]) { [[WebImageManager sharedManager] cancelDownload:self.urlStr]; // 如果 ImageView 之前有图像-清空图像 self.image = nil; } // 记录新的 url self.urlStr = urlString; __weak typeof(self) weakSelf = self; // 下载网络图片 [[WebImageManager sharedManager] downloadImage:self.urlStr completion:^(UIImage *image) { weakSelf.image = image; }]; } // 向分类添加属性 // 运行时的关联对象，动态添加属性 const void *URLStrKey = "URLStrKey"; - (void)setUrlStr:(NSString *)urlString { objc_setAssociatedObject(self, URLStrKey, urlString, OBJC_ASSOCIATION_COPY_NONATOMIC); } - (NSString *)urlStr { return objc_getAssociatedObject(self, URLStrKey); } -
SwiftImageCache-Bridging-Header.h
#import "UIImageView+WebImageView.h" -
ViewController.swift
// 懒加载 lazy var dataSourceArray:[AnyObject] = { var tmp:[AnyObject] = AppInfoModel.loadPList() return tmp }() // 表格视图数据源方法 override func tableView(tableView: UITableView, numberOfRowsInSection section: Int) -> Int { return self.dataSourceArray.count } override func tableView(tableView: UITableView, cellForRowAtIndexPath indexPath: NSIndexPath) -> UITableViewCell { let cell:AppInfoCell = tableView.dequeueReusableCellWithIdentifier("AppCell", forIndexPath: indexPath) as! AppInfoCell let dataModel = self.dataSourceArray[indexPath.row] as! AppInfoModel cell.nameLabel.text = dataModel.name cell.downLabel.text = dataModel.download cell.iconView.setWebImageWithURL(dataModel.icon) return cell }
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5、SDWebImage 缓存方式
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Github 网址：https://github.com/rs/SDWebImage
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SDWebImage 使用 ARC
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Objective-C
// 添加第三方库文件 SDWebImage // 包含头文件 #import "UIImageView+WebCache.h"-
AppInfoModel.h
@interface AppInfoModel : NSObject /// 标题名称 @property (nonatomic, strong) NSString *name; /// 下载数量 @property (nonatomic, strong) NSString *download; /// 图片地址 @property (nonatomic, strong) NSString *icon; /// 从 Plist 加载 AppInfo + (NSArray *)loadPList; @end -
AppInfoModel.m
+ (NSArray *)loadPList { NSArray *array = [NSArray arrayWithContentsOfURL:[[NSBundle mainBundle] URLForResource:@"apps.plist" withExtension:nil]]; NSMutableArray *plist = [NSMutableArray arrayWithCapacity:array.count]; [array enumerateObjectsUsingBlock:^(id obj, NSUInteger idx, BOOL *stop) { id model = [[self alloc] init]; [model setValuesForKeysWithDictionary:obj]; [plist addObject:model]; }]; return plist; } -
AppInfoCell.h
@interface AppInfoCell : UITableViewCell @property (nonatomic, weak) IBOutlet UILabel *nameLabel; @property (nonatomic, weak) IBOutlet UILabel *downloadLabel; @property (nonatomic, weak) IBOutlet UIImageView *iconImageView; @end -
ViewController.m
/// 表格数据源 @property (nonatomic, strong) NSArray *dataSourceArray; // 懒加载 - (NSArray *)dataSourceArray { if (_dataSourceArray == nil) { _dataSourceArray = [AppInfoModel loadPList]; } return _dataSourceArray; } // 表格视图数据源方法 - (NSInteger)tableView:(UITableView *)tableView numberOfRowsInSection:(NSInteger)section { return self.dataSourceArray.count; } - (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath { AppInfoCell *cell = [tableView dequeueReusableCellWithIdentifier:@"AppCell" forIndexPath:indexPath]; AppInfoModel *dataModel = self.dataSourceArray[indexPath.row]; cell.nameLabel.text = dataModel.name; cell.downloadLabel.text = dataModel.download; [cell.iconImageView sd_setImageWithURL:[NSURL URLWithString:dataModel.icon]]; return cell; }
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Swift
// 添加第三方库文件 SDWebImage // 创建桥接头文件，如 SwiftImageCache-Bridging-Header.h // 在桥接头文件中添加头文件 #import "UIImageView+WebCache.h"-
AppInfoModel.swift
class AppInfoModel: NSObject var name:String! var icon:String! var download:String! class func loadPList() -> [AnyObject] { let array = NSArray(contentsOfURL: NSBundle.mainBundle().URLForResource("apps.plist", withExtension: nil)!) var plist:[AnyObject] = Array() array!.enumerateObjectsUsingBlock { (obj:AnyObject, idx:Int, stop:UnsafeMutablePointer<ObjCBool>) in let model:AnyObject = self.init() model.setValuesForKeysWithDictionary(obj as! [String : AnyObject]) plist.append(model) } return plist } class func AppInfoWithDict(dict:[String:AnyObject]) -> AnyObject { let obj:AnyObject = self.init() obj.setValuesForKeysWithDictionary(dict) return obj } required override init() { super.init() } -
AppInfoCell.swift
class AppInfoCell: UITableViewCell @IBOutlet weak var iconView: UIImageView! @IBOutlet weak var nameLabel: UILabel! @IBOutlet weak var downLabel: UILabel! -
ViewController.swift
// 懒加载 lazy var dataSourceArray:[AnyObject] = { var tmp:[AnyObject] = AppInfoModel.loadPList() return tmp }() // 表格视图数据源方法 override func tableView(tableView: UITableView, numberOfRowsInSection section: Int) -> Int { return self.dataSourceArray.count } override func tableView(tableView: UITableView, cellForRowAtIndexPath indexPath: NSIndexPath) -> UITableViewCell { let cell:AppInfoCell = tableView.dequeueReusableCellWithIdentifier("AppCell", forIndexPath: indexPath) as! AppInfoCell let dataModel = self.dataSourceArray[indexPath.row] as! AppInfoModel cell.nameLabel.text = dataModel.name cell.downLabel.text = dataModel.download // 设置图片 cell.iconView.sd_setImageWithURL(NSURL(string: dataModel.icon)) return cell }
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