Cache Image From URL working, but returns blank image?

Question

I have two methods, first checks if I've already downloaded the image, and if not retrieves the image from a URL and caches it to my docs directory in my app. If it has been, it simply retrieves it, and if I have a internet connection, will re-download it. Here are the two methods:

- (UIImage *) getImageFromUserIMagesFolderInDocsWithName:(NSString *)nameOfFile
{
    UIImage *image = [UIImage imageNamed:nameOfFile];
    if (!image) // image doesn't exist in bundle...
    {
        // Get Image
        NSString *cleanNameOfFile = [[[nameOfFile stringByReplacingOccurrencesOfString:@"." withString:@""]
                                                  stringByReplacingOccurrencesOfString:@":" withString:@""]
                                                  stringByReplacingOccurrencesOfString:@"/" withString:@""];

        NSString *filePath = [NSHomeDirectory() stringByAppendingPathComponent:[NSString stringWithFormat:@"Documents/%@.png", cleanNameOfFile]];
        image = [[UIImage alloc] initWithData:[NSData dataWithContentsOfFile:filePath]];
        if (!image)
        {
            // image isn't cached
            image = [UIImage imageWithData:[NSData dataWithContentsOfURL:[NSURL URLWithString:nameOfFile]]];
            [self saveImageToUserImagesFolderInDocsWithName:cleanNameOfFile andImage:image];
        }
        else
        {
            // if we have a internet connection, update the cached image
            /*if (isConnectedToInternet) {
                image = [UIImage imageWithData:[NSData dataWithContentsOfURL:[NSURL URLWithString:nameOfFile]]];
                [self saveImageToUserImagesFolderInDocsWithName:cleanNameOfFile andImage:image];
            }*/
            // otherwise just return it
        }
    }
    return image;
}

Here's to save the image

- (void) saveImageToUserImagesFolderInDocsWithName:(NSString *)nameOfFile andImage:(UIImage *)image
{
    NSString *pngPath = [NSHomeDirectory() stringByAppendingPathComponent:[NSString stringWithFormat:@"Documents/%@.png", nameOfFile]];
    [UIImagePNGRepresentation(image) writeToFile:pngPath atomically:YES];


    NSLog(@"directory: %@", [[UIImage alloc] initWithContentsOfFile:pngPath]);
}

The image has already been successfully downloaded and cached to my documents directory (I know because I can see it in the File system). And it successfully re loads the image the first time I call this method, but once I go to another view, and re-call this method when I come back to the same view, it's blank. Yet, the URL is correct. What's wrong here?

score 0 · Answer 1 · answered Sep 29 '12 at 17:23

0

Maybe, you should do:

image = [UIImage imageWithContentsOfFile: nameOfFile];

answered Sep 29 '12 at 17:23

Andrey

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I've tried that as well (in place of returning it as nsdata then initializing it) same thing happens. – ManOx Sep 29 '12 at 17:25
Have you tracked `filePath` and `pngPath` variables? – Andrey Sep 29 '12 at 17:28

score 0 · Accepted Answer · edited May 23 '17 at 10:24

1) You should not be writing into a hardcoded path as you do (ie "Documents/xxx"), but rather ask for the Application Support directory, use it, and also mark files so that they don't get uploaded to iCloud (unless you want that). See this link on the specifics. Create a subfolder in it and mark it as not for iCloud backup.

2) Try changing:

image = [UIImage imageWithData:[NSData dataWithContentsOfURL:[NSURL URLWithString:nameOfFile]]];

to

image = [UIImage imageWithData:[NSData dataWithContentsOfURL:[NSURL URLWithString:filePath]]];

Cache Image From URL working, but returns blank image?

2 Answers2