实现iOS图片等资源的热更新化(四) 一个最小化的补丁更新逻辑.doc

实现iOS图片等资源文件的热更新化(四): 一个最小化的补丁更新逻辑这么做的意义先交代动机和意义,或许应该成为自己博客的一个标准框架内容之一,不然以后自己需要看着,也不过是一堆干瘪的代码.基本的逻辑图,如上!此处,我就从简!从简的原因有3:补丁更新,状态可以设计的很复杂,就像开头那篇文章提到的那样,但是我感觉没多大必要,至少在我们的App中;我想演示一个相对完整的逻辑,但是又不想耗费太多的时间构建场景;从简后的方案,简单但够用了,至少目前针对我们的项目来说;所以说:这篇文章的意义,其实是在于简化已有的热更新代码,越简单越好维护.基本思路App启动时,判断特定的服务器接口所返回的图片url是否为最新,判断方式就是比对返回值中的md5字段与本地保存的资源的url是否一致;如果图片资源有更新,则下载解压到指定的缓存目录,初步打算以资源文件的md5来划分文件夹,来避免冲突;读取图片时,优先从缓存目录读取,缓存目录不存在再从ipa资源包中读取;下面就一步一步来实现了.App启动时,判断有无最新图片资源此处主要涉及到的可能的技术点:1. 如何用基础的网络类库发送网络请求?先简单封装一个函数来获取,用到了block.block经常用,但到现在都记不太清形式,大都是从其他处copy下,然后改改参数.记不住,也懒得记!- (void)fetchPatchInfo:(NSString *) urlStr completionHandler:(void ()(NSDictionary * patchInfo, NSError * error)completionHandler NSURLSessionConfiguration * defaultConfigObject = NSURLSessionConfiguration defaultSessionConfiguration; NSURLSession * defaultSession = NSURLSession sessionWithConfiguration: defaultConfigObject delegate: self delegateQueue: NSOperationQueue mainQueue; NSURL * url = NSURL URLWithString:urlStr; NSURLSessionDataTask * dataTask = defaultSession dataTaskWithURL:url completionHandler:(NSData * data, NSURLResponse * response, NSError * error) NSDictionary * patchInfo = NSJSONSerialization JSONObjectWithData:data options:0 error:&error; completionHandler(patchInfo, error); ; dataTask resume; 基于block,调用的代码也就很简答了.self fetchPatchInfo: /ios122/ios_assets_hot_update/master/res/patch_04.json completionHandler:(NSDictionary * patchInfo, NSError * error) if ( ! error) NSLog(patchInfo:%, patchInfo); else NSLog(fetchPatchInfo error: %, error); ; 好吧,我承认AFNetworking用习惯了,好久没用原始的网络请求的代码了,有点low,莫怪!2. 如何校验下载的文件的md5值,如果你需要的话?开头那篇文章链接里,有提到.核心,其实是在于下载文件之后,md5值的计算,剩余的就是字符串比较操作了.注意要先引入系统库1#include /* * 获取文件的md5信息. * * param path 文件路径. * * return 文件的md5值. */-(NSString *)mcMd5HashOfPath:(NSString *)path NSFileManager * fileManager = NSFileManager defaultManager; / 确保文件存在. if( fileManager fileExistsAtPath:path isDirectory:nil ) NSData * data = NSData dataWithContentsOfFile:path; unsigned char digestCC_MD5_DIGEST_LENGTH; CC_MD5( data.bytes, (CC_LONG)data.length, digest ); NSMutableString * output = NSMutableString stringWithCapacity:CC_MD5_DIGEST_LENGTH * 2; for( int i = 0; i CC_MD5_DIGEST_LENGTH; i+ ) output appendFormat:%02x, digesti; return output; else return ; 3. 使用什么保存与获取本地缓存资源的md5等信息?好吧,我打算直接使用用户配置文件,NSString * source_patch_key = SOURCE_PATCH; NSUserDefaults standardUserDefaults setObject:patchInfo forKey: source_patch_key;patchInfo = NSUserDefaults standardUserDefaults objectForKey: source_patch_key; NSLog(patchInfo:%, patchInfo); 补丁下载与解压此处主要涉及到的可能的技术点:1. 如何基于图片缓存信息来找到指定的缓存目录?问题本身有些绕口,其实我想做的就是根据补丁的md5,放到不同的缓存文件夹,如补丁md5为 e963ed645c50a004697530fa596f180b,则对应放到 patch/e963ed645c50a004697530fa596f180b 文件夹.封装一个简单的根据md5返回缓存路径的方法吧:- (NSString *)cachePathFor:(NSString * )patchMd5 NSArray * LibraryPaths = NSSearchPathForDirectoriesInDomains(NSLibraryDirectory, NSUserDomainMask, YES); NSString * cachePath = LibraryPaths objectAtIndex:0 stringByAppendingFormat:/Caches/patch stringByAppendingPathComponent:patchMd5; return cachePath; 使用时,类似这样:NSString * urlStr = patchInfo objectForKey: url; weak_self downloadFileFrom:urlStr completionHandler:(NSURL * location, NSError * error) if (error) NSLog(download file url:% error: %, urlStr, error); return; NSString * cachePath = weak_self cachePathFor: patchInfo objectForKey:md5; NSLog(location:% cachePath:%,location, cachePath); ; 2. 如何解压文件到指定目录?如果需要安装 CocoaPods ,建议使用 brew:1brew install CocoaPods 解压本身推荐 SSZipArchive 库,一行代码搞定:1SSZipArchive unzipFileAtPath:location.path toDestination: patchCachePath overwrite:YES password:nil error:&error; 3. 在什么时候更新本地的缓存资源的相关信息?建议是在下载并解压资源文件到指定缓存目录后,再更新补丁的相关缓存信息,因为这个信息,读取图片时,也是需要的.如果删除某个补丁,按照目前的设计,一种比较偷懒的方案就是,在服务器上放上一个新的空资源文件就可以了.NSString * source_patch_key = SOURCE_PATCH; NSUserDefaults standardUserDefaults setObject:patchInfo forKey: source_patch_key; 读取图片功能扩展此处主要涉及到的可能的技术点:1. 如何用基础的网络类库下载文件?依然是要封装一个简单函数,下载完成后,通过block传出文件临时的保存位置:-(void) downloadFileFrom:(NSString * ) urlStr completionHandler: (void ()(NSURL *location, NSError * error) completionHandler NSURL * url = NSURL URLWithString:urlStr; NSURLSessionConfiguration * defaultConfigObject = NSURLSessionConfiguration defaultSessionConfiguration; NSURLSession * defaultSession = NSURLSession sessionWithConfiguration: defaultConfigObject delegate:self delegateQueue: NSOperationQueue mainQueue; NSURLSessionDownloadTask * downloadTask = defaultSession downloadTaskWithURL:url completionHandler:(NSURL * location, NSURLResponse * response, NSError * error) completionHandler(location,error); ; downloadTask resume; 2. 如何判断bundle中是否含有某文件?可以使用 fileExistsAtPath,但其实使用 -pathForResource: ofType: 就够了,因为找不到资源问加你时,它返回nil,所以我们直接调用它,然后判断返回是否为 nil 即可:1NSString * imgPath = mainBundle pathForResource:imgName ofType:png; 3. 将代码如何与原有的imageNamed:逻辑合并?不需要初始复制到缓存目录 + 初始请求最新的资源补丁信息 + 代码迁移合并 + 接口优化相对完整的逻辑代码注意,按照目前的设计,就不需要初始把原来ipa中的bundle复制到缓存目录了;当缓存目录中没有相关资源时,会自动尝试从ipa中的bundle读取,bundle约定统一使用 main.bundle 来简化操作,类目,对外暴露两个方法:#import interface UIImage (imageNamed_bundle_)/* load img smart .*/+ (UIImage *)yf_imageNamed:(NSString *)imgName; /* smart update for patch */+ (void)yf_updatePatchFrom:(NSString *) pathInfoUrlStr;end App启动时,或在其他合适的地方,要注意检查有无更新:- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions / Override point for customization after application launch. /* fetch pathc info every time */ NSString * patchUrlStr = /ios122/ios_assets_hot_update/master/res/patch_04.json; UIImage yf_updatePatchFrom: patchUrlStr; return YES; 内部实现,优化了许多,但也算不上复杂:#import UIImage+imageNamed_bundle_.h#import implementation UIImage (imageNamed_bundle_) + (NSString *)yf_sourcePatchKey return SOURCE_PATCH; + (void)yf_updatePatchFrom:(NSString *) pathInfoUrlStr self yf_fetchPatchInfo: pathInfoUrlStr completionHandler:(NSDictionary *patchInfo, NSError *error) if (error) NSLog(fetchPatchInfo error: %, error); return; NSString * urlStr = patchInfo objectForKey: url; NSString * md5 = patchInfo objectForKey:md5; NSString * oriMd5 = NSUserDefaults standardUserDefaults objectForKey: self yf_sourcePatchKey objectForKey:md5; if (oriMd5 isEqualToString:md5) / no update return; self yf_downloadFileFrom:urlStr completionHandler:(NSURL *location, NSError *error) if (error) NSLog(download file url:% error: %, urlStr, error); return; NSString * patchCachePath = self yf_cachePathFor: md5; SSZipArchive unzipFileAtPath:location.path toDestination: patchCachePath overwrite:YES password:nil error:&error; if (error) NSLog(unzip and move file error, with urlStr:% error:%, urlStr, error); return; /* update patch info. */ NSString * source_patch_key = self yf_sourcePatchKey; NSUserDefaults standardUserDefaults setObject:patchInfo forKey: source_patch_key; ; ; + (NSString *)yf_relativeCachePathFor:(NSString *)md5 return patch stringByAppendingPathComponent:md5; + (UIImage *)yf_imageNamed:(NSString *)imgName NSString * bundleName = main; /* cache dir */ NSString * md5 = NSUserDefaults standardUserDefaults objectForKey: self yf_sourcePatchKey objectForKey:md5; NSString * relativeCachePath = self yf_relativeCachePathFor: md5; return self yf_imageNamed: imgName bundle:bundleName cacheDir: relativeCachePath; + (UIImage *)yf_imageNamed:(NSString *)imgName bundle:(NSString *)bundleName cacheDir:(NSString *)cacheDir NSArray * LibraryPaths = NSSearchPathForDirectoriesInDomains(NSLibraryDirectory, NSUserDomainMask, YES); bundleName = NSString stringWithFormat:%.bundle,bundleName; NSString * ipaBundleDir = NSBundle mainBundle.resourcePath; NSString * cacheBundleDir = ipaBundleDir; if (cacheDir) cacheBundleDir = LibraryPaths objectAtIndex:0 stringByAppendingFormat:/Caches stringByAppendingPathComponent:cacheDir; imgName = NSString stringWithFormat:%3x,imgName; NSString * bundlePath = cacheBundleDir stringByAppendingPathComponent: bundleName; NSBundle * mainBundle = NSBundle bundleWithPath:bundlePath; NSString * imgPath = mainBundle pathForResource:imgName ofType:png; /* try load from ipa! */ if ( ! imgPath & ! ipaBundleDir isEqualToString: cacheBundleDir) bundlePath = ipaBundleDir stringByAppendingPathComponent: bundleName; mainBundle = NSBundle WithPath:bundlePath; imgPath = mainBundle pathForResource:imgName ofType:png; UIImage * image; static NSString * model; if (!model) model = UIDevice currentDevicemodel; if (model isEqualToString:iPad) NSData * imageData = NSData dataWithContentsOfFile: imgPath; image = UIImage imageWithData:imageData scale:2.0; else image = UIImage imageWithContentsOfFile: imgPath; return image; + (void)yf_fetchPatchInfo:(NSString *) urlStr completionHandler:(void ()(NSDictionary * patchInfo, NSError * error)completionHandler NSURLSessionConfiguration *defaultConfigObject = NSURLSessionConfiguration defaultSessionConfiguration; NSURLSession *defaultSession = NSURLSession sessionWithConfiguration: defaultConfigObject delegate: nil delegateQueue: NSOperationQueue mainQueue; NSURL * url = NSURL URLWithString:urlStr; NSURLSessionDataTask * dataTask = defaultSession dataTaskWithURL:url completionHandler:(NSData *data, NSURLResponse *response, NSError *error) NSDictionary * patchInfo = NSJSONSerialization JSONObjectWithData:data options:0 error:&error; completionHandler(patchInfo, error); ; dataTask resume; + (void) yf_downloadFileFrom:(NSStr