ASIHTTPRequest 断点续传

最近学习ASIHTTPRequest如何使用,所以利用ASIHTTPRequest自身的功能,写了个可断点下载的小demo

我利用tableview作为下载列表,所有自己custom了一个cell,用来控制下载

enum DownloadStatus {
    DownloadNotStart = 0,
    Downloading,
    DownloadPause,
    DownloadFinish
};

@interface DownloadFileListTableViewCell : UITableViewCell <ASIHTTPRequestDelegate, ASIProgressDelegate>{
    UIProgressView *_progressView;
    UIButton *_controlButton;
    UILabel *_sizeTip;
    
    ASIHTTPRequest *_asiRequest;
    NSURL *_oriURL;
    enum DownloadStatus _downloadStatus;
    NSString *_saveFilePath;
    NSString *_tmpFilePath;
    
    long long _curSize;
    long long _totalSize;
}

最新的 ASIHTTPRequest 自己有一个支持断点下载的方法,

    [_asiRequest setTemporaryFileDownloadPath:_tmpFilePath];
    [_asiRequest setAllowResumeForFileDownloads:YES];

只要设置了这两个,就可以实现断点下载

下面是我自己实现的几个控制下载的方法

- (void)startDownload
{
    _curSize = 0;
    _totalSize = 0;
    
    _asiRequest = [[ASIHTTPRequest alloc] initWithURL:_oriURL];
    [_asiRequest setDelegate:self];
    [_asiRequest setDownloadProgressDelegate:self];
    [_asiRequest setShowAccurateProgress:YES];
    [_asiRequest setDownloadDestinationPath:_saveFilePath];
    [_asiRequest setTemporaryFileDownloadPath:_tmpFilePath];
    [_asiRequest setAllowResumeForFileDownloads:YES];
    
    _downloadStatus = Downloading;
    [_controlButton setTitle:@"Pause" forState:UIControlStateNormal];
    [_asiRequest startAsynchronous];
}

- (void)pauseDownload
{
    [_asiRequest clearDelegatesAndCancel];
    [_asiRequest release], _asiRequest = nil;
    _downloadStatus = DownloadPause;
    [_controlButton setTitle:@"Resume" forState:UIControlStateNormal];
}

- (void)resumeDownload
{
    _curSize = 0;
    
    _asiRequest = [[ASIHTTPRequest alloc] initWithURL:_oriURL];
    [_asiRequest setDelegate:self];
    [_asiRequest setDownloadProgressDelegate:self];
    [_asiRequest setShowAccurateProgress:YES];
    [_asiRequest setDownloadDestinationPath:_saveFilePath];
    [_asiRequest setTemporaryFileDownloadPath:_tmpFilePath];
    [_asiRequest setAllowResumeForFileDownloads:YES];
    
    _downloadStatus = Downloading;
    [_controlButton setTitle:@"Pause" forState:UIControlStateNormal];
    [_asiRequest startAsynchronous];
}

- (void)finishDownload
{
    [_controlButton setTitle:@"Finish" forState:UIControlStateNormal];
    _downloadStatus = DownloadFinish;
    NSLog(@"success Finish Download");
}

因为要利用progressview手动记录下载情况,所以,继承了ASIProgressDelegate,并实现了

- (void)request:(ASIHTTPRequest *)request didReceiveBytes:(long long)bytes
{
    // when resume download, the bytes is the size of the file which had down
    _curSize += bytes;
    
    float value = (_curSize*1.0)/(_totalSize*1.0);
    [_progressView setProgress:value];
    
    float tmp = 1024*1024.0;
    NSString *tip = [NSString stringWithFormat:@"%.1lf/%.1lfM", _curSize/tmp, _totalSize/tmp];
    [_sizeTip setText:tip];
}

这样,就可以随时记录下载情况了.

写这个demo的过程中,还遇到了url redirect的问题,ASIHTTPRequest本身是可以auto redirect的,但是不知什么原因,我这里并没有auto redirect,所以,我自己手动控制它redirect(实现ASIHTTPRequestDelegate的requestFailed方法)

- (void)requestFailed:(ASIHTTPRequest *)request
{
    NSError *error = [request error];
    [_controlButton setTitle:@"Fail" forState:UIControlStateNormal];
    NSLog(@"Failed error : %@", [error localizedDescription]);
    
    NSDictionary *resp = [request responseHeaders];
    NSString *redirectURL = [resp valueForKey:@"Location"];
    if([request responseStatusCode] == 302 && redirectURL){
        [self redirectToDest:redirectURL];
    }
}

当然,status code = 301的时候也需要redirect,我这里就没加上了.

到这里,我还遇到个问题就是,每次下载都定死了文件名,当下载多个文件时,会导致文件重写,所以,要时不同文件不重复,且能很好的辨认,最后的办法就是能从头部中获取服务端返回的文件名,并以此命名.但是,在ASIHTTPRequet的responseHeader中却找不到这个值.经google后得知,需要自己解析header 的 Content-Disposition.所以,我想获取ASIHTTPRequest刚获取的header,不知怎么获取.