ASIHTTPRequest 断点续传-优快云博客

本文链接：https://blog.youkuaiyun.com/focusjava/article/details/10402265

http://code4app.com/ios/Hayate/4fe32cb96803fa6a72000001

一、创建网络请求队列

首先，创建网络请求队列，如下：

ASINetworkQueue *que = [[ASINetworkQueue alloc] init];

self.netWorkQueue = que;

[que release];

[self.netWorkQueue reset];

[self.netWorkQueue setShowAccurateProgress:YES];

[self.netWorkQueue go];

二、创建存放路径

//初始化Documents路径

NSString *path = [NSHomeDirectory() stringByAppendingPathComponent:@"Documents"];

//初始化临时文件路径

NSString *folderPath = [path stringByAppendingPathComponent:@"temp"];

//创建文件管理器

NSFileManager *fileManager = [NSFileManager defaultManager];

//判断temp文件夹是否存在

BOOL fileExists = [fileManager fileExistsAtPath:folderPath];

if (!fileExists) {//如果不存在说创建,因为下载时,不会自动创建文件夹

[fileManager createDirectoryAtPath:folderPath

withIntermediateDirectories:YES

attributes:nil

error:nil];

}

三、发送下载请求

这里对下面几个对象说明一下：CustomCell是我自定义的cell，cell上面有下载和暂停两个按钮，其tag值为cell所在的行，因此这里的[sendertag]为下载按钮的tag值，self.downloadArray为array数组对象，存放要下载的资源字典信息，在该字典中有一键为URL，它对应的值就是我们下载链接。

这些东西，根据自己的实际需要改动一下即可使用

CustomCell *cell = (CustomCell *)[self.myTableView cellForRowAtIndexPath:[NSIndexPath indexPathForRow:[sender tag] inSection:0]];

NSString *filePath = [[self.downloadArray objectAtIndex:[sender tag]] objectForKey:@"URL"];

NSLog(@"filePath=%@",filePath);

//初始下载路径

NSURL *url = [NSURL URLWithString:filePath];

//设置下载路径

ASIHTTPRequest *request = [[ASIHTTPRequest alloc] initWithURL:url];

//设置ASIHTTPRequest代理

request.delegate = self;

//初始化保存ZIP文件路径

NSString *savePath = [path stringByAppendingPathComponent:[NSString stringWithFormat:@"book_%d.zip",[sender tag]]];

//初始化临时文件路径

NSString *tempPath = [path stringByAppendingPathComponent:[NSString stringWithFormat:@"temp/book_%d.zip.temp",[sender tag]]];

//设置文件保存路径

[request setDownloadDestinationPath:savePath];

//设置临时文件路径

[request setTemporaryFileDownloadPath:tempPath];

//设置进度条的代理,

[request setDownloadProgressDelegate:cell];

//设置是是否支持断点下载

[request setAllowResumeForFileDownloads:YES];

//设置基本信息

[request setUserInfo:[NSDictionary dictionaryWithObjectsAndKeys:[NSNumber numberWithInt:[sender tag]],@"bookID",nil]];

NSLog(@"UserInfo=%@",request.userInfo);

//添加到ASINetworkQueue队列去下载

[self.netWorkQueue addOperation:request];

//收回request

[request release];

三、暂停请求

这里的cell下下载时的一样，

CustomCell *cell = (CustomCell *)[self.myTableView cellForRowAtIndexPath:[NSIndexPath indexPathForRow:[sender tag] inSection:0]];

for (ASIHTTPRequest *request in [self.netWorkQueue operations]) {

NSInteger bookid = [[request.userInfo objectForKey:@"bookID"] intValue];//查看userinfo信息

if ([sender tag] == bookid) {//判断ID是否匹配

//暂停匹配对象

[request clearDelegatesAndCancel];

}

四、ASIHTTPRequestDelegate回调方法

上面已经把下载请求与暂停请求实现，点击下载时，开始下载资源；当点暂停时，下载中断；当我们再点击下载按钮时，继续下载，在第二步的

[request setAllowResumeForFileDownloads:YES]设置是是否支持断点下载。下面要实现ASIHTTPRequestDelegate代理方法如下：

#pragma mark -

#pragma mark ASIHTTPRequestDelegate method

//ASIHTTPRequestDelegate,下载之前获取信息的方法,主要获取下载内容的大小，可以显示下载进度多少字节

- (void)request:(ASIHTTPRequest *)request didReceiveResponseHeaders:(NSDictionary *)responseHeaders {

NSLog(@"didReceiveResponseHeaders-%@",[responseHeaders valueForKey:@"Content-Length"]);

NSLog(@"contentlength=%f",request.contentLength/1024.0/1024.0);

int bookid = [[request.userInfo objectForKey:@"bookID"] intValue];

NSUserDefaults *userDefaults = [NSUserDefaults standardUserDefaults];

float tempConLen = [[userDefaults objectForKey:[NSString stringWithFormat:@"book_%d_contentLength",bookid]] floatValue];

NSLog(@"tempConLen=%f",tempConLen);

//如果没有保存,则持久化他的内容大小

if (tempConLen == 0 ) {//如果没有保存,则持久化他的内容大小

[userDefaults setObject:[NSNumber numberWithFloat:request.contentLength/1024.0/1024.0] forKey:[NSString stringWithFormat:@"book_%d_contentLength",bookid]];

}

//ASIHTTPRequestDelegate,下载完成时,执行的方法

- (void)requestFinished:(ASIHTTPRequest *)request {

int bookid = [[request.userInfo objectForKey:@"bookID"] intValue];

CustomCell *cell = (CustomCell *)[self.myTableView cellForRowAtIndexPath:[NSIndexPath indexPathForRow:bookid inSection:0]];

cell.downloadCompleteStatus = YES;

cell.progressView.progress = 0.0;

}

经过上述步骤，一个支持断点续传的功能程序实现了！

HTTP断点续传的基本原理

断点续传是我们现在经常接触的概念，那么HTTP协议是如何支持断点续传的呢。我们先从一个例子来看看。

下面是一个断点续传的例子：（使用Net Vampire得到）

I 01-7-12 19:19:23 ------------------------- Attempt 1 -------------------------
P 01-7-12 19:19:24 Connecting to 127.0.0.3 ...
P 01-7-12 19:19:24 Connected to 127.0.0.3 [127.0.0.3]
S 01-7-12 19:19:24 GET /VS0515AI.EXE HTTP/1.1
S 01-7-12 19:19:24 Connection: close
S 01-7-12 19:19:24 Host: 127.0.0.3
S 01-7-12 19:19:24 Accept: */*
S 01-7-12 19:19:24 Pragma: no-cache
S 01-7-12 19:19:24 Cache-Control: no-cache
S 01-7-12 19:19:24 Referer: http://127.0.0.3/
S 01-7-12 19:19:24 User-Agent: Mozilla/4.04 [en] (Win95; I ;Nav)
S 01-7-12 19:19:24
R 01-7-12 19:19:24 HTTP/1.1 200 OK
R 01-7-12 19:19:24 Server: Zero Http Server/1.0
R 01-7-12 19:19:24 Date: Thu, 12 Jul 2001 11:19:24 GMT
R 01-7-12 19:19:24 Cache-Control: no-cache
R 01-7-12 19:19:24 Last-Modified: Tue, 30 Jan 2001 13:11:30 GMT
R 01-7-12 19:19:24 Content-Type: application/octet-stream
R 01-7-12 19:19:24 Content-Length: 15143086
R 01-7-12 19:19:24 Connection: close
R 01-7-12 19:19:24
P 01-7-12 19:19:25 Data transfer started
I 01-7-12 19:19:32 Job Stopped by user
I 01-7-12 19:19:33 Received 5 275 648 bytes in 0:00:07 (691 435 bytes/s)

I 01-7-12 19:19:40 ------------------------- Attempt 2 -------------------------
P 01-7-12 19:19:40 Connecting to 127.0.0.3 ...
P 01-7-12 19:19:40 Connected to 127.0.0.3 [127.0.0.3]
S 01-7-12 19:19:40 GET /VS0515AI.EXE HTTP/1.1
S 01-7-12 19:19:40 Connection: close
S 01-7-12 19:19:40 Host: 127.0.0.3
S 01-7-12 19:19:40 Accept: */*
S 01-7-12 19:19:40 Pragma: no-cache
S 01-7-12 19:19:40 Cache-Control: no-cache
S 01-7-12 19:19:40 Referer: http://127.0.0.3/
S 01-7-12 19:19:40 User-Agent: Mozilla/4.04 [en] (Win95; I ;Nav)
S 01-7-12 19:19:40 Range: bytes=5275648-
S 01-7-12 19:19:40
R 01-7-12 19:19:40 HTTP/1.1 206 Partial Content
R 01-7-12 19:19:40 Server: Zero Http Server/1.0
R 01-7-12 19:19:40 Date: Thu, 12 Jul 2001 11:19:40 GMT
R 01-7-12 19:19:40 Cache-Control: no-cache
R 01-7-12 19:19:40 Last-Modified: Tue, 30 Jan 2001 13:11:30 GMT
R 01-7-12 19:19:40 Content-Type: application/octet-stream
R 01-7-12 19:19:40 Content-Range: bytes 5275648-15143085/15143086
R 01-7-12 19:19:40 Content-Length: 9867438
R 01-7-12 19:19:40 Connection: close
R 01-7-12 19:19:40
P 01-7-12 19:19:40 Data transfer started
I 01-7-12 19:19:41 Job Stopped by user
I 01-7-12 19:19:41 Received 1 124 756 bytes in 0:00:01 (969 617 bytes/s)

第一次是普通的传输；第二次由于没有传完全，就发出了Range这个头部，从5275648字节开始传输（默认是按字节算），回应使用206状态值，表示现在开始部分传输，回复Content-Length头部，表示传输的部分，用字节记，然后就与普通传输没有区别了。

NSUrlConnection实现断点续传的关键是自定义http request的头部的range域属性。

　Range头域
　　Range头域可以请求实体的一个或者多个子范围。例如，
　　表示头500个字节：bytes=0-499
　　表示第二个500字节：bytes=500-999
　　表示最后500个字节：bytes=-500
　　表示500字节以后的范围：bytes=500-
　　第一个和最后一个字节：bytes=0-0,-1
　　同时指定几个范围：bytes=500-600,601-999
　　但是服务器可以忽略此请求头，如果无条件GET包含Range请求头，响应会以状态码206（PartialContent）返回而不是以200（OK）。

在ios中使用NSMutableURLRequest来定义头部域

NSURL *url1=[NSURL URLWithString:@"下载地址";
NSMutableURLRequest* request1=[NSMutableURLRequest requestWithURL:url1];
[request1 setValue:@"bytes=20000-" forHTTPHeaderField:@"Range"];
[request1 setCachePolicy:NSURLRequestReloadIgnoringLocalCacheData];
NSData *returnData1 = [NSURLConnection sendSynchronousRequest:request1 returningResponse:nil error:nil];
[self writeToFile:returnData1 fileName:@"SOMEPATH"];
-(void)writeToFile:(NSData *)data fileName:(NSString *) fileName
{
NSString *filePath=[NSString stringWithFormat:@"%@",fileName];
if([[NSFileManager defaultManager] fileExistsAtPath:filePath] == NO){
NSLog(@"file not exist,create it...");
[[NSFileManager defaultManager] createFileAtPath:filePath contents:nil attributes:nil];
}else {
NSLog(@"file exist!!!");
}
FILE *file = fopen([fileName UTF8String], [@"ab+" UTF8String]);
if(file != NULL){
fseek(file, 0, SEEK_END);
}
int readSize = [data length];
fwrite((const void *)[data bytes], readSize, 1, file);
fclose(file);
}

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