如何保存从网址下载的视频？

Question

我想保存之前从网址下载过的视频。 我使用此代码，当我点击下载按钮时，我将从URL下载视频。我使用连接方法，并在最后我使用NSFileManager保存视频数据。  问题是我创建了一个文件路径，但在其中没有任何类型的数据。我该如何解决？

-(IBAction)download:(id)sender{

    /*[downloadButton setEnabled:NO];
     [webView setUserInteractionEnabled:NO];*/

    //Prendo URL
    NSString *getURL = @"";

    getURL = [webView stringByEvaluatingJavaScriptFromString:@"function getURL() {var player = document.getElementById('player'); var video = player.getElementsByTagName('video')[0]; return video.getAttribute('src');} getURL();"];

    //Prendo il titolo
    videoTitle = videoTitleField.text;
    NSArray *components = [videoTitle componentsSeparatedByCharactersInSet:[[NSCharacterSet alphanumericCharacterSet] invertedSet]];
    videoTitle = [components componentsJoinedByString:@" "];

    if ([getURL length] > 0) {
        if ([videoTitle length] > 0) {
            //videoTitle = [getTitle retain];

            fileURL = [NSURL URLWithString:getURL];
            downloadUrl = fileURL;
            bytesReceived = percentComplete = 0;
            localFilename = [[[fileURL absoluteString] lastPathComponent] copy];
            receivedData = [[NSMutableData alloc] initWithLength:0];

            app.networkActivityIndicatorVisible = YES;
            //Inserisco alert view
            alert = [[UIAlertView alloc] initWithTitle:@"Download" message:[NSString stringWithFormat:@"%.2f",percentComplete] delegate:nil cancelButtonTitle:nil otherButtonTitles:nil];
            [alert show];

            //Connessione download
            DownloadRequest = [[NSURLRequest alloc] initWithURL:fileURL cachePolicy:NSURLRequestReloadIgnoringLocalCacheData timeoutInterval:15];
            DownloadConnection = [[NSURLConnection alloc] initWithRequest:DownloadRequest delegate:self startImmediately:YES];


        }
        else{
            //Utente non inserisce il nome per il video
            UIAlertView *alertview = [[UIAlertView alloc] initWithTitle:@"TubeDownloader" message:@"You have to insert a name for the video!" delegate:nil cancelButtonTitle:@"OK" otherButtonTitles:nil];
            [alertview show];
        }
    }else {
        //Non si riesce a prendere URL
        UIAlertView *alertView1 = [[UIAlertView alloc] initWithTitle:@"TubeDownloader" message:@"Couldn't get MP4 URL." delegate:nil cancelButtonTitle:@"OK" otherButtonTitles:nil];
        [alertView1 show];

        [downloadButton setEnabled:YES];
    }

}


-(void) connection:(NSURLConnection *)connection didReceiveData:(NSData *)data{

    if(!operationBreaked){

        [self.receivedData appendData:data];
        //[self.receivedData setData:data];
        float receivedLen = [data length];
        NSLog(@"receive lenght: %f\n",receivedLen);

        bytesReceived = (bytesReceived + receivedLen);

        if(expectedBytes != NSURLResponseUnknownLength){

            //progressView.progress = ((bytesReceived/(float)expectedBytes)*100)/100;
            percentComplete = (((bytesReceived/(float)expectedBytes)*100)/100) * 100;

        }

        NSLog(@"Ricevendo dati..percentuale di completamento:%f",percentComplete);
        [alert setMessage:[NSString stringWithFormat:@"Percentage:%.2f",percentComplete]];

    }else{
        [connection cancel];
        NSLog(@"Ricezione dati cancellata...percentuale:%f",percentComplete);
    }
         [self.receivedData appendData:data];
}

-(void) connection:(NSURLConnection *)connection didFailWithError:(NSError *)error{
    operationFailed = YES;
    //progressView.progress = 0.0;
}

-(void) connection:(NSURLConnection *)connection didReceiveResponse:(NSURLResponse *)response{

    NSLog(@"Bytes aspettati: %f... Bytes ricevuti:%f\n",(float)expectedBytes,(float)bytesReceived);

    NSHTTPURLResponse *r = (NSHTTPURLResponse*) response;//An NSHTTPURLResponse object represents a response to an HTTP URL load request. It’s a subclass of NSURLResponse that provides methods for accessing information specific to HTTP protocol responses.

    NSDictionary *headers = [r allHeaderFields];//headerFields:a dictionary representing the keys and values from the server’s response header.

    NSLog(@"[DO::didReceiveResponse] response headers: %@", headers);
    if (headers){
        if ([headers objectForKey: @"Content-Range"]) {
            NSString *contentRange = [headers objectForKey: @"Content-Range"];
            NSLog(@"Content-Range: %@", contentRange);
            NSRange range = [contentRange rangeOfString: @"/"];
            NSString *totalBytesCount = [contentRange substringFromIndex: range.location + 1];
            expectedBytes = [totalBytesCount floatValue];
        } else if ([headers objectForKey: @"Content-Length"]) {
            NSLog(@"Content-Length: %@", [headers objectForKey: @"Content-Length"]);
            expectedBytes = [[headers objectForKey: @"Content-Length"] floatValue];
        } else expectedBytes = -1;

        if ([@"Identity" isEqualToString: [headers objectForKey: @"Transfer-Encoding"]]) {
            expectedBytes = bytesReceived;
            operationFinished = YES;
        }
    }
}

-(void)connectionDidFinishLoading:(NSURLConnection *)connection{
    NSLog(@"connessione terminata con successo receive data:%f!!",bytesReceived);
    operationFinished = YES;
    [alert setMessage:@"Download been succesfully"];

    app.networkActivityIndicatorVisible = NO;

    //NSData *saveData = [NSData dataWithBytes:&receivedData length:sizeof(receivedData)];
    //Attivo timer per dimettere il timer
    [NSTimer scheduledTimerWithTimeInterval:1 target:self selector:@selector(dismissAlert) userInfo:nil repeats:NO];

    //[self.receivedData setData:];
    //Chiamo la funzione di salvataggio passandogli come NSData receivedata e localfileName
    //[self saveVideo:self.receivedData];
    NSFileManager *fileManager = [NSFileManager defaultManager];
    NSArray *path = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES);
    NSString *pathdir = [NSString stringWithFormat:@"%@.mp4", [[path objectAtIndex:0] stringByAppendingPathComponent:videoTitle]];

    NSLog(@"pathDir: %@",pathdir);
    [fileManager createFileAtPath:pathdir contents:receivedData attributes:nil];

    NSString *imagePath = [NSString stringWithFormat:@"%@.mp4", [[path objectAtIndex:0]stringByAppendingPathComponent:videoTitle]];

    AVAsset *asset = [[AVURLAsset alloc] initWithURL:[NSURL fileURLWithPath:[NSString stringWithFormat:@"%@.mp4",[[path objectAtIndex:0] stringByAppendingPathComponent:videoTitle]]] options:nil]; //AVAsset is an abstract class to represent timed audiovisual media such as videos and sounds. Each asset contains a collection of tracks that are intended to be presented or processed together, each of a uniform media type, including but not limited to audio, video, text, closed captions, and subtitles.

    AVAssetImageGenerator *imageGenerator = [[AVAssetImageGenerator alloc] initWithAsset:asset]; //An AVAssetImageGenerator object provides thumbnail or preview images of assets independently of playback. AVAssetImageGenerator uses the default enabled video track(s) to generate images.

    Float64 durationSeconds = CMTimeGetSeconds(asset.duration);

    CMTime midpoint = CMTimeMakeWithSeconds(durationSeconds / 2.0, 600);
    CMTime actualTime;

    CGImageRef preImage = [imageGenerator copyCGImageAtTime:midpoint actualTime:&actualTime error:NULL];

    if (preImage != NULL) {
        CGRect rect = CGRectMake(0.0, 0.0, CGImageGetWidth(preImage) * 0.5, CGImageGetHeight(preImage) * 0.5);

        UIImage *image = [UIImage imageWithCGImage:preImage];

        UIGraphicsBeginImageContext(rect.size);

        [image drawInRect:rect];

        NSData *data = UIImagePNGRepresentation(UIGraphicsGetImageFromCurrentImageContext());

        [fileManager createFileAtPath:imagePath contents:data attributes:nil];

        UIGraphicsEndImageContext();
    }

    CGImageRelease(preImage);

    //videoTitle = nil;

    NSLog(@"Salvataggio con successo");
}