iPhone image save from web issues

Question

I have code that will check to see if an image is on the phone or not (the name being retrieved from the db), and if not, it runs this code:

NSString *urlString = [NSString stringWithFormat: @"http://www.vegashipster.com/%@",image_path];                        
NSData *imageData = [[NSData alloc] initWithData:[NSData dataWithContentsOfURL:[NSURL URLWithString:urlString]]];

NSLog(@"saving jpg");
UIImage *image = [[UIImage alloc] initWithData:imageData];//1.0f = 100% quality

[UIImageJPEGRepresentation(image, 1.0f) writeToFile:myFilePath atomically:YES];
NSLog(@"saving image done");
NSLog(@"URL String: %@",urlString);
NSLog(@"http://www.vegashipster.com/%@",image_path);

rest_image = [UIImage imageNamed:image_path];

[image release];
[imageData release];

This code works just fine on the simulator, but on the iPhone, the screen freezes for a few seconds (downloading the image, I think), then loads the page, but with no image visible. The next time you hit that page, there is no freeze. So I believe the file is being created, but it's a messed up image file, and therefore not displayed.

I've already broken this code up so that it runs in it's own thread, and again, it works in the simulator. I had thought that if it ran behind the scenes, there would be less of a chance that the image data would get messed up, but the exact same thing happens (minus the freezing). Does anyone know what I am doing wrong with this code? Thanks for any and all help/comments.

Edit

And yes, the images being downloaded are strictly .jpg

Edit 2

I seen:

Make sure you are writing to your DOCUMENTS directory, which you have read+write access to. Otherwise you won't get any files.

at http://www.iphonedevsdk.com/forum/iphone-sdk-development/15628-file-weirdness-files-written-disk-do-not-appear-nsfilemanager-defaultmanager.html . Could this be my issue?

NSString *image_path = [[NSString stringWithUTF8String:(char *)sqlite3_column_text(statement, 5)] stringByReplacingOccurrencesOfString:@"../"
NSString *myFilePath = [[[NSBundle mainBundle] resourcePath] stringByAppendingPathComponent:image_path];

Last Edit

Well, I found what I believe to be my answer at How can I get a writable path on the iPhone? . It pretty much states I cannot save image files where my own image files are located inside the build. If this is incorrect, please let me know and I will try your way.

Answer 1

NSData *imageData = [[NSData alloc] initWithData:[NSData dataWithContentsOfURL:[NSURL URLWithString:urlString]]];

Is a synchronous call, ie it blocks until it has fully executed, which in the case of network operations can be 1 second, 10 seconds or 3 minutes if you don't have a time out. You are presumably running this on the main thread which is why your UI freezes (all UI stuff is done on the main thread so you must do everything not to block it). The reason it doesn't freeze the next time around is probably that it has cached the image data.

You should use asynchronous APIs, NSURLConnection has some, however I strongly recommend ASIHTTPRequest, which is an obj c wrapper around NSURLConnection and co. The code would look something like this (read through the how to use section)

- (IBAction)grabURLInBackground:(id)sender
{
   NSURL *url = [NSURL URLWithString:@"http://allseeing-i.com"];
   ASIHTTPRequest *request = [ASIHTTPRequest requestWithURL:url];
   [request setDelegate:self];
   [request startAsynchronous];
}

- (void)requestFinished:(ASIHTTPRequest *)request
{
   // Use when fetching text data
   NSString *responseString = [request responseString];

   // Use when fetching binary data
   NSData *responseData = [request responseData];
   UIImage* downloadedImage = [UIImage imageWithData:responseData];
}

- (void)requestFailed:(ASIHTTPRequest *)request
{
   NSError *error = [request error];
}

Answer 2

Sorry, forgot about this thread completely. I did end up fixing this issue. Here is what I did:

NSFileManager* fileManager = [NSFileManager defaultManager];

NSArray *paths = NSSearchPathForDirectoriesInDomains(NSLibraryDirectory, NSUserDomainMask, YES);
NSString *libraryDirectory = [paths objectAtIndex:0];

NSString *myFilePath = [libraryDirectory stringByAppendingPathComponent:image_path];

BOOL fileExists = [fileManager fileExistsAtPath:myFilePath];

if (fileExists){
    hotel_image = [UIImage imageWithContentsOfFile:myFilePath];
}else{
    [NSThread detachNewThreadSelector:@selector(downloadImage:) toTarget:[HotelsDetailsViewController class] withObject:image_path];

    fileExists = [fileManager fileExistsAtPath:myFilePath];

    if (fileExists){
        hotel_image = [UIImage imageWithContentsOfFile:myFilePath];
    }else{
        hotel_image = [UIImage imageNamed:@"hdrHotels.jpg"];
    }
}

In short, I found my app's library directory and saved there.