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 = @"<img[^>]+?
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;
}