1、ImageCache
-
使用内存缓存方式：
-
使用沙盒缓存方式：
-
使用网络图片第三方库方式：
-
SDWebImage：
iOS 中著名的网络图片处理框架
包含的功能：图片下载、图片缓存、下载进度监听、gif 处理等等
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
国内超过 90% 的 iOS 项目都有它的影子
-
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
-
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！
md5
如果单纯使用 文件名保存，重名的几率很高！
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！
-
8、SDWebImage 的内存警告是如何处理的！
利用通知中心观察
UIApplicationDidReceiveMemoryWarningNotification 接收到内存警告的通知
执行 clearMemory 方法，清理内存缓存！
UIApplicationWillTerminateNotification 接收到应用程序将要终止通知
执行 cleanDisk 方法，清理磁盘缓存！
UIApplicationDidEnterBackgroundNotification 接收到应用程序进入后台通知
执行 backgroundCleanDisk 方法，后台清理磁盘！
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！
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！
-
bug:
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。
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！
-
2、自定义内存缓存方式
-
Objective-C
-
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];
}
-
-
Swift
-
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()
}
-
3、自定义沙盒缓存方式
-
Objective-C
AppInfoModel.h
AppInfoModel.m
-
AppInfoCell.h
- 与上边一样
-
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
-
Swift
AppInfo.swift
-
AppInfoCell.swift
- 与上边一样
-
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
4、仿 SDWebImage 缓存方式
-
Objective-C
-
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;
}
-
-
Swift
-
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
}
-
5、SDWebImage 缓存方式
Github 网址：https://github.com/rs/SDWebImage
SDWebImage 使用 ARC
-
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;
}
-
-
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
}
-