Objective C: Downloading File With Progress Bar [duplicate]

问题

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• how to display progressbar during downloading video file from the server in to the iphone? 1 answer

I am trying to put a progress bar that syncs during the download that is happening. My app now can download a file using with this codes...

    pdfData = [[NSData alloc] initWithContentsOfURL:[NSURL URLWithString:@\"http://webaddress.com/pro/download/file.pdf\"]];

    NSString *resourcePDFPath = [[NSString alloc] initWithString:[[[[NSBundle mainBundle]  resourcePath] stringByDeletingLastPathComponent] stringByAppendingPathComponent:@\"Documents\"]];

    pdfFilePath = [resourcePDFPath stringByAppendingPathComponent:@\"myPDF.pdf\"];

    [pdfData writeToFile:pdfFilePath atomically:YES];

During the process of this code the app stopped during download, is it normal? Now what I want is to put a progress bar during that stop time while downloading.

I tried looking into the codes I found online but I\'m a bit confused, I think I need a step-by-step-well-explained reference.

回答1:

Using AFNetworking,

here progress is the UIProgressview

#import <AFNetworking/AFNetworking.h>//add to the header of class

-(void)downloadShowingProgress
{
   progress.progress = 0.0;

    currentURL=@"http://www.selab.isti.cnr.it/ws-mate/example.pdf";


    NSURLRequest *request = [NSURLRequest requestWithURL:[NSURL URLWithString:currentURL]];
    AFURLConnectionOperation *operation =   [[AFHTTPRequestOperation alloc] initWithRequest:request];

    NSArray *paths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES);
    NSString *filePath = [[paths objectAtIndex:0] stringByAppendingPathComponent:@"MY_FILENAME_WITH_EXTENTION.pdf"];
    operation.outputStream = [NSOutputStream outputStreamToFileAtPath:filePath append:NO];

    [operation setDownloadProgressBlock:^(NSUInteger bytesRead, NSUInteger totalBytesRead, NSUInteger totalBytesExpectedToRead) {
        progress.progress = (float)totalBytesRead / totalBytesExpectedToRead;

    }];

    [operation setCompletionBlock:^{
        NSLog(@"downloadComplete!");

    }];
    [operation start];

}

Using NSURLConnection

-(void)downloadWithNsurlconnection
{

    NSURL *url = [NSURL URLWithString:currentURL];
    NSURLRequest *theRequest = [NSURLRequest requestWithURL:url         cachePolicy:NSURLRequestReloadIgnoringLocalCacheData timeoutInterval:60];
    receivedData = [[NSMutableData alloc] initWithLength:0];
    NSURLConnection * connection = [[NSURLConnection alloc] initWithRequest:theRequest delegate:self     startImmediately:YES];


}


- (void) connection:(NSURLConnection *)connection didReceiveResponse:(NSURLResponse *)response {
    [UIApplication sharedApplication].networkActivityIndicatorVisible = YES;
    progress.hidden = NO;
    [receivedData setLength:0];
    expectedBytes = [response expectedContentLength];
}

- (void) connection:(NSURLConnection *)connection didReceiveData:(NSData *)data {
    [receivedData appendData:data];
    float progressive = (float)[receivedData length] / (float)expectedBytes;
    [progress setProgress:progressive];


}

- (void) connection:(NSURLConnection *)connection didFailWithError:(NSError *)error {
    [UIApplication sharedApplication].networkActivityIndicatorVisible = NO;

}

- (NSCachedURLResponse *) connection:(NSURLConnection *)connection willCacheResponse:    (NSCachedURLResponse *)cachedResponse {
    return nil;
}

- (void) connectionDidFinishLoading:(NSURLConnection *)connection {
    NSArray *paths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES);

    NSString *documentsDirectory = [paths objectAtIndex:0];
    NSString *pdfPath = [documentsDirectory stringByAppendingPathComponent:[currentURL stringByAppendingString:@".mp3"]];
    NSLog(@"Succeeded! Received %d bytes of data",[receivedData length]);
    [UIApplication sharedApplication].networkActivityIndicatorVisible = NO;
    [receivedData writeToFile:pdfPath atomically:YES];
    progress.hidden = YES;
}

回答2:

Use ASIHTTPRequest.h class and ASINetworkQueue.h for downloading the file.

and use this code for progress bar

    request = [ASIHTTPRequest requestWithURL:@"http://webaddress.com/pro/download/file.pdf];
    [request setDelegate:self];
    [request setDownloadProgressDelegate:progressView];
    [request setShowAccurateProgress:YES];
    request.shouldContinueWhenAppEntersBackground=YES;
    request.allowResumeForFileDownloads=YES;
    [request startAsynchronous];

this may help you

回答3:

I'm afraid it's not normal, use asynchronous method to get the NSData.

回答4:

First of all you should be clear whether to make a synchronous call or asynchronous. For mobile apps or any other app asynchronous is preferred one.

Once you are clear use NSURLConnection class to fetch the data from the URL. Here is the good tutorial.

And for loading you can start progress while starting the request and stop it when you receive connection:didFailWithError: or connectionDidFinishLoading: delegate method.

来源：https://stackoverflow.com/questions/16453655/objective-c-downloading-file-with-progress-bar