上次写过用ASIHTTPRequest做断点续传的例子。但是一个是写的比较搓。一个是ASIHTTPRequest库已经不在维护。最后是扩展性不是很好。所以花了很长时间改写用MKNetworkKit来写。
如果需要回顾一下ASIHTTPRequest的断点续传的在这里
下载地址是
https://github.com/MugunthKumar/MKNetworkKit
作者本人的臭屁介绍在这里
- 首先把clone下来的MKNetworkKit文件夹拖进你的项目里面
- 到项目里面增加CFNetwork.Framework SystemConfiguration.framework 和 Security.framework.
- 把MKNetworkKit.h包含到你的pch文件里面。
- 如果是iOS，删除NSAlert+MKNetworkKitAdditions.h这个文件
- 如果是Mac，删除UIAlertView+MKNetworkKitAdditions.h这个文件
这样，再看看介绍里面的例子。应该就能看懂普通用法了。然后畅快的使用MKNetworkKit库了。
上次写的ASIHTTPRequest续传其实已经可以用了。但是为什么需要重新写呢。就是重用！！！
一直都很少自己设计接口什么的。其实只是做了写体力的劳动，把一堆逻辑换成代码给堆了起来。觉得没有人会去重用自己的代码。很少去花心思想怎么样才能写好。
这次改写就只有一个目标，为了更好更多人能使用断点续传来下载。
下载的持久化的微观含义是在push到新的view或者pop出当前view。下载应该在后台继续进行。 宏观含义是按home把程序放入后台以后，下载继续进行。
每次进入下载的view的时候progressview都应该保持一致
可以随时暂停下载和恢复下载
这次改写，这些功能都实现了，啊哈哈哈。
最开始使用MKNetworkKit库做下载的时候，progressview的数值一直不对。经过boss的观察，应该是某个东西写错地方了。然后 修改了某两个函数才可以的。详细如下： 找到MKNetworkOperation.m文件
- (void)connection:(NSURLConnection *)connection didReceiveResponse:(NSURLResponse *)response {
NSUInteger size = [self.response expectedContentLength] < 0 ? 0 : [self.response expectedContentLength];
self.response = (NSHTTPURLResponse*) response;
// dont' save data if the operation was created to download directly to a stream.
if([self.downloadStreams count] == 0)
self.mutableData = [NSMutableData dataWithCapacity:size];
else
self.mutableData = nil;
for(NSOutputStream *stream in self.downloadStreams)
[stream open];
NSDictionary *httpHeaders = [self.response allHeaderFields];
// if you attach a stream to the operation, MKNetworkKit will not cache the response.
// Streams are usually "big data chunks" that doesn't need caching anyways.
if([self.request.HTTPMethod isEqualToString:@"GET"] && [self.downloadStreams count] == 0) {
// We have all this complicated cache handling since NSURLRequestReloadRevalidatingCacheData is not implemented
// do cache processing only if the request is a "GET" method
NSString *lastModified = [httpHeaders objectForKey:@"Last-Modified"];
NSString *eTag = [httpHeaders objectForKey:@"ETag"];
NSString *expiresOn = [httpHeaders objectForKey:@"Expires"];
NSString *contentType = [httpHeaders objectForKey:@"Content-Type"];
// if contentType is image,
NSDate *expiresOnDate = nil;
if([contentType rangeOfString:@"image"].location != NSNotFound) {
// For images let's assume a expiry date of 7 days if there is no eTag or Last Modified.
if(!eTag && !lastModified)
expiresOnDate = [[NSDate date] dateByAddingTimeInterval:kMKNetworkKitDefaultImageCacheDuration];
else
expiresOnDate = [[NSDate date] dateByAddingTimeInterval:kMKNetworkKitDefaultImageHeadRequestDuration];
}
NSString *cacheControl = [httpHeaders objectForKey:@"Cache-Control"]; // max-age, must-revalidate, no-cache
NSArray *cacheControlEntities = [cacheControl componentsSeparatedByString:@","];
for(NSString *substring in cacheControlEntities) {
if([substring rangeOfString:@"max-age"].location != NSNotFound) {
// do some processing to calculate expiresOn
NSString *maxAge = nil;
NSArray *array = [substring componentsSeparatedByString:@"="];
if([array count] > 1)
maxAge = [array objectAtIndex:1];
expiresOnDate = [[NSDate date] dateByAddingTimeInterval:[maxAge intValue]];
}
if([substring rangeOfString:@"no-cache"].location != NSNotFound) {
// Don't cache this request
expiresOnDate = [[NSDate date] dateByAddingTimeInterval:kMKNetworkKitDefaultCacheDuration];
}
}
// if there was a cacheControl entity, we would have a expiresOnDate that is not nil.
// "Cache-Control" headers take precedence over "Expires" headers
expiresOn = [expiresOnDate rfc1123String];
// now remember lastModified, eTag and expires for this request in cache
if(expiresOn)
[self.cacheHeaders setObject:expiresOn forKey:@"Expires"];
if(lastModified)
[self.cacheHeaders setObject:lastModified forKey:@"Last-Modified"];
if(eTag)
[self.cacheHeaders setObject:eTag forKey:@"ETag"];
}
if ([self.mutableData length] == 0 || [self.downloadStreams count] > 0) {
// This is the first batch of data
// Check for a range header and make changes as neccesary
NSString *rangeString = [[self request] valueForHTTPHeaderField:@"Range"];
if ([rangeString hasPrefix:@"bytes="] && [rangeString hasSuffix:@"-"]) {
NSString *bytesText = [rangeString substringWithRange:NSMakeRange(6, [rangeString length] - 7)];
self.startPosition = [bytesText integerValue];
self.downloadedDataSize = self.startPosition;
DLog(@"Resuming at %d bytes", self.startPosition);
}
}
}
- (void)connection:(NSURLConnection *)connection didReceiveData:(NSData *)data {
if([self.downloadStreams count] == 0)
[self.mutableData appendData:data];
for(NSOutputStream *stream in self.downloadStreams) {
if ([stream hasSpaceAvailable]) {
const uint8_t *dataBuffer = [data bytes];
[stream write:&dataBuffer[0] maxLength:[data length]];
}
}
self.downloadedDataSize += [data length];
for(MKNKProgressBlock downloadProgressBlock in self.downloadProgressChangedHandlers) {
if([self.response expectedContentLength] > 0) {
double progress = (double)(self.downloadedDataSize) / (double)(self.startPosition + [self.response expectedContentLength]);
downloadProgressBlock(progress);
}
}
}具体改了哪，忘记了。有心思对照源码看看。应该是属于MKNetworkKit的bug。也不知道新版改过来没有。但是你clone我的demo，这个版本是可以的。
其实我一共就写了两个简单的类而已。
基础的是SIBreakpointsDownload。继承于MKNetworkOperation。判断了续传的位置。
一个SIDownloadManager写成单例，继承于MKNetworkEngine。用来管理多任务下载。
使用的时候就只用SIDownloadManager这个类来添加下载，暂停下载。然后想在下载的前后、出错时候、progressview改变时候对view作出改变。就实现它的delegate就好了。
demo地址
git@github.com:iiiyu/SIDownloader.git
其实已经很简单了，照着demo改改就能自己用了。
这次改写以后，代码结构变的很清晰。复杂性和耦合性都有所降低。可用性提高。而且，反正我是没有google到可以直接拿来用的断点下载库。这次娃哈哈就有了。然后blog也2月没有更新，鄙视自己。以后应该会慢慢更新恢复正常。最后，希望对大家有所帮助。