Establish a view of progress in a cycle or update a view of progress

Question

for (int i=0; i<[array count]; i++)
{
    NSError *error;
    NSArray *ipaths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES);
    NSString *idocumentsDir = [ipaths objectAtIndex:0];
    NSString *idataPath = [idocumentsDir stringByAppendingPathComponent:@"File"];
    NSLog(@"idataPath:%@",idataPath);

    //Create folder here
    if (![[NSFileManager defaultManager] fileExistsAtPath:idataPath])
    {
        [[NSFileManager defaultManager] createDirectoryAtPath:idataPath withIntermediateDirectories:NO attributes:nil error:&error];
    }
    // Image Download here
    NSString *fileName = [idataPath stringByAppendingFormat:@".jpg"];
    NSLog(@"imagePathDOWNLOAD:%@",fileName);

    _imgData = [[NSData alloc] initWithContentsOfURL:[NSURL URLWithString:[array objectAtIndex:i]]];
    [_imgData writeToFile:fileName atomically:YES];

    tempImg.image = [UIImage imageWithData:_imgData];   
}

How to set up a progress view for this loop, I want to set up a progress view for loading data. as well as a progress label (i.e.%). I want percent decimal numbers.

Answer 1

A simple solution is to do this asynchronously, updating the view of progress as you move:

• Create a progress view and add it to your view

• Send your code to the background

• As each download completes, send the progress view update back to the main queue

In pseudo code, it will look like

UIProgressView *progressView = [[UIProgressView alloc] init];
// configure the progress view and add it to your UI

dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0), ^{
    for (int i=0; i<[array count]; i++)
    {
        NSError *error;
        NSArray *ipaths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES);
        NSString *idocumentsDir = [ipaths objectAtIndex:0];
        NSString *idataPath = [idocumentsDir stringByAppendingPathComponent:@"File"];
        NSLog(@"idataPath:%@",idataPath);

        //Create folder here
        if (![[NSFileManager defaultManager] fileExistsAtPath:idataPath])
        {
            [[NSFileManager defaultManager] createDirectoryAtPath:idataPath withIntermediateDirectories:NO attributes:nil error:&error];
        }
        // Image Download here
        NSString *fileName = [idataPath stringByAppendingFormat:@".jpg"];
        NSLog(@"imagePathDOWNLOAD:%@",fileName);

        _imgData = [[NSData alloc] initWithContentsOfURL:[NSURL URLWithString:[array objectAtIndex:i]]];
        [_imgData writeToFile:fileName atomically:YES];

        // now dispatch any UI updates back to the main queue
        dispatch_async(dispatch_get_main_queue(), ^{

            [progressView setProgress: (CGFloat) (i + 1.0) / [array count] animated:YES];
            tempImg.image = [UIImage imageWithData:_imgData];
        });
    }
});

:

• ( , ) , . maxConcurrentCount 5, concurrency, , iOS .

• NSURLConnectionDataDelegate, NSData initWithContentsOfURL, . . .

• AFNetworking, .

---

, 1, , . GCD 3-4 NSOperationQueue, .

GCD:

CFAbsoluteTime start = CFAbsoluteTimeGetCurrent();

UIProgressView *progressView = [self addProgressView];

dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0), ^{

    NSInteger downloadSuccessCount = 0;
    NSInteger downloadFailureCount = 0;

    NSString *idataPath = [self createDownloadPath];

    for (int i = 0; i < [array count]; i++)
    {
        // Image Download here
        NSString *filename = [self pathForItem:i array:array folder:idataPath];
        NSURL *url = [self urlForItem:i array:array];
        NSData *data = [[NSData alloc] initWithContentsOfURL:url];
        UIImage *image = nil;
        if (data)
            image = [UIImage imageWithData:data];
        if (image) {
            downloadSuccessCount++;
            [data writeToFile:filename atomically:YES];
        } else {
            downloadFailureCount++;
        }

        // now dispatch any UI updates back to the main queue
        dispatch_async(dispatch_get_main_queue(), ^{

            [progressView setProgress: (CGFloat) (downloadSuccessCount + downloadFailureCount) / [array count] animated:YES];

            // update the image in the UI if you want

            [UIView transitionWithView:self.imageView duration:0.25 options:UIViewAnimationOptionTransitionCrossDissolve animations:^{
                tempImg.image = image;
            } completion:nil];
        });
    }

    NSLog(@"Completed in %.1f seconds", CFAbsoluteTimeGetCurrent() - start);
});

NSOperationQueue:

CFAbsoluteTime start = CFAbsoluteTimeGetCurrent();

UIProgressView *progressView = [self addProgressView];

NSOperationQueue *queue = [[NSOperationQueue alloc] init];
queue.maxConcurrentOperationCount = 5;

NSString *idataPath = [self createDownloadPath];
self.downloadSuccessCount = 0;
self.downloadFailureCount = 0;

NSOperation *completionOperation = [NSBlockOperation blockOperationWithBlock:^{
    NSLog(@"Completed in %.1f seconds", CFAbsoluteTimeGetCurrent() - start);
}];

for (int i = 0; i < [array count]; i++)
{
    NSOperation *operation = [NSBlockOperation blockOperationWithBlock:^{
        // Image Download here
        NSString *filename = [self pathForItem:i array:array folder:idataPath];
        NSURL *url = [self urlForItem:i array:array];
        NSData *data = [NSData dataWithContentsOfURL:url];
        UIImage *image = nil;
        if (data)
            image = [UIImage imageWithData:data];
        if (image)
            [data writeToFile:filename atomically:YES];

        // now dispatch any UI updates back to the main queue
        [[NSOperationQueue mainQueue] addOperationWithBlock:^{

            if (image) {
                self.downloadSuccessCount++;

                // update the image in the UI if you want, though this slows it down

                [UIView transitionWithView:self.imageView duration:0.25 options:UIViewAnimationOptionTransitionCrossDissolve animations:^{
                    tempImg.image = image;
                } completion:nil];
            }
            else
                self.downloadFailureCount++;

            [progressView setProgress: (CGFloat) (self.downloadSuccessCount + self.downloadFailureCount) / [array count] animated:YES];
        }];
    }];

    [queue addOperation:operation];
    [completionOperation addDependency:operation];
}

[queue addOperation:completionOperation];

, NSOperationQueue ( concurrency, GCD, ( )), .

, , AFNetworking, concurrency, .

Answer 2

[progressView setProgress: (CGFloat) (i + 1.0) / [array count] animated:YES];
self.progressLabel.text = [NSString stringWithFormat:@"%.0f",self.progressView.progress*100];