UIwebView实现html的离线缓存

1、html的缓存主要採取ASIHTTPRequest的缓存策略

（1）、设置缓存策略

//设置缓存

ASIDownloadCache *cache=[[ASIDownloadCache alloc] init];

self.myCache=cache;

//设置缓存路径

NSArray *paths =NSSearchPathForDirectoriesInDomains(NSDocumentDirectory,NSUserDomainMask, YES);

NSString *documentDirectory = [paths objectAtIndex:0];

//设置缓存存放路径

[self.myCache setStoragePath:[documentDirectory stringByAppendingPathComponent:@"resource"]];

//ASIAskServerIfModifiedCachePolicy 与默认缓存大致一样。差别仅是每次请求都会 去server推断是否有更新

//ASIOnlyLoadIfNotCachedCachePolicy 假设有缓存在本地，无论其过期与否。总会拿来使用

//ASIFallbackToCacheIfLoadFailsCachePolicy 这个选项常常被用来与其他选项组合使用。请求失败时，假设有缓存当网络则返回本地缓存信息

[self.myCache setDefaultCachePolicy:ASIFallbackToCacheIfLoadFailsCachePolicy]; //设置缓存策略

（2）、设置异步缓存

NSURL *Requesturl=[NSURL URLWithString:url];

ASIHTTPRequest *request=[ASIHTTPRequest requestWithURL:Requesturl];

// //获取全局变量

AppDelegate *appDelegate = [[UIApplication sharedApplication] delegate];

// //设置缓存方式

[request setDownloadCache:appDelegate.myCache];

// //设置缓存数据存储策略。这里採取的是假设无更新或无法联网就读取缓存数据

[request setCacheStoragePolicy:ASICachePermanentlyCacheStoragePolicy];

[request setDelegate:self];

[request startAsynchronous];

html缓存完毕。如想查看具体 请点击 ： IOS开发网络篇之──ASIHTTPRequest具体解释

2、html中的图片缓存

（1）、通过正则获取html代码中的全部图片url

NSString *urlPattern = @"]+?src=[\"']?([^>'\"]+)[\"']?";

NSError *error = [NSError new];

NSRegularExpression *regex = [NSRegularExpression regularExpressionWithPattern:urlPattern options:NSRegularExpressionCaseInsensitive error:&error ];

//match 这块内容很强大

NSUInteger counts =[regex numberOfMatchesInString:content options:NSRegularExpressionCaseInsensitive range:NSMakeRange(0, [content length])];//匹配到的次数

if(counts > 0){

NSArray* matches = [regex matchesInString:content options:NSMatchingReportCompletion range:NSMakeRange(0, [content length])];

for (NSTextCheckingResult *match in matches) {

NSInteger count = [match numberOfRanges];//匹配项

for(NSInteger index = 0;index < count;index++){

NSRange halfRange = [match rangeAtIndex:index];

if (index == 1) {

//[listImage addObject:[content substringWithRange:halfRange]];

NSLog(@"转换出来的字符串＝＝＝%@",[content substringWithRange:halfRange]);

[listImage addObject:[content substringWithRange:halfRange]];

}

}

}//遍历后能够看到三个range。1、为总体。2、为([\\w-]+\\.)匹配到的内容。3、([\\w.%&=-]*)匹配到的内容

}

（2）、SDwebImage下载图片 、JS交互替换

dispatch_queue_t queue = dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0ul);

dispatch_group_t group = dispatch_group_create();

for (int i = 0; i < listImage.count; i++)

{

NSString *imageUrl = [imageUrlArray objectAtIndex:i];

NSString *key=[self getMd5_32Bit_String:imageUrl];

UIImage *cachedImage=[[SDImageCache sharedImageCache] imageFromDiskCacheForKey:key];

NSString *index = [NSString stringWithFormat:@"%d", i];

if (cachedImage) {

[tchWebView stringByEvaluatingJavaScriptFromString:[self createSetImageUrlJavaScript:index

imgUrl:key]];

}else{

dispatch_group_async(group, queue, ^{

//异步下载图片

[SDWebImageDownloader.sharedDownloader downloadImageWithURL:[NSURL URLWithString:imageUrl]

options:0

progress:^(NSInteger receivedSize, NSInteger expectedSize)

{

// progression tracking code

}

completed:^(UIImage *image, NSData *data, NSError *error, BOOL finished)

{

if (image && finished)

{

[[SDImageCache sharedImageCache] storeImage:image forKey:key];

dispatch_sync(dispatch_get_main_queue(), ^{

[tchWebView stringByEvaluatingJavaScriptFromString:[self createSetImageUrlJavaScript:index

imgUrl:key]];

});

}

}];

});

}

}

dispatch_release(group);

//设置下载完毕的图片到web img

- (NSString *)createSetImageUrlJavaScript:(NSString *) index imgUrl:(NSString *) url{

UIImage *myCachaImage=[[SDImageCache sharedImageCache] imageFromDiskCacheForKey:url];

NSData *imageData = UIImageJPEGRepresentation(myCachaImage,1.0);

NSString *imageSource = [NSString stringWithFormat:@"data:image/jpg;base64,%@",[imageData base64Encoding]];

NSString *js = [NSString stringWithFormat:@"var imgArray = document.getElementsByTagName('img'); imgArray[%@].src=\"%@\"; " , index, imageSource];

return js;

}

//32位MD5加密方式

- (NSString *)getMd5_32Bit_String:(NSString *)srcString{

const char *cStr = [srcString UTF8String];

unsigned char digest[CC_MD5_DIGEST_LENGTH];

CC_MD5( cStr, strlen(cStr), digest );

NSMutableString *result = [NSMutableString stringWithCapacity:CC_MD5_DIGEST_LENGTH * 2];

for(int i = 0; i < CC_MD5_DIGEST_LENGTH; i++)

[result appendFormat:@"%02x", digest[i]];

return result;

}

參考：http://bbs.csdn.net/topics/390831054

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