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Hello all, I'm trying to download images asynchronously then display them when downloaded. I'm using the same principles to do it as thisThis tutorial. The problem is that when I run the app for the first time all the images are either "pixel noise", the same image over and over, or partly loaded with some pixels in the image scrambled. I also get errors in the console like:
ImageIO: PNG Extra compressed data
ImageIO: PNG invalid block type
ImageIO: PNG invalid distance too far back
After the first time loading it all works fine with all the images rendering properly and no console errors. This happens whether I set the cache policy to not allow, allow, or anything in between.
This isn't a problem with the actual images. I have saved the PNG's as non-interlaced, re-saved the images to make sure nothing was wrong, and loaded a lot of different images from Google images. The problem remains.
And if I try changing the file to to JPG's the same problem occurs but the console just spits out different error messages.
This isn't a problem with the actual images. I have saved the PNG's as non-interlaced, re-saved the images to make sure nothing was wrong, and loaded a lot of different images from Google images. The problem remains.
Sounds like it's a problem with your code then!
Seriously though, if you want people to help you debug your code, you'll need to show the code. Preferably reduced down to the bare minimum that can reproduce the bug. I would suggest you also break down your problem a little bit more. Analyze your async http request first, and then the UI component.
Seriously though, if you want people to help you debug your code, you'll need to show the code. Preferably reduced down to the bare minimum that can reproduce the bug. I would suggest you also break down your problem a little bit more. Analyze your async http request first, and then the UI component.
Sorry for not including it at the beginning. The method loadImages is caleld when the view loads.
I don't see anywhere in your code where you tell the view that it needs to be refreshed. From the Apple View Programming Documentation Loading
View drawing occurs on an as-needed basis. . . When the actual content of your view changes, it is your responsibility to notify the system that your view needs to be redrawn. You do this by calling your views setNeedsDisplay or setNeedsDisplayInRect: method of the view. These methods let the system know that it should update the view during the next drawing cycle.
This would explain why you are getting odd results the first time around, but then later (i.e. when the view is redrawn) everything looks fine.
Shredder2794
Posts: 9New Users
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Seriously though, if you want people to help you debug your code, you'll need to show the code. Preferably reduced down to the bare minimum that can reproduce the bug. I would suggest you also break down your problem a little bit more. Analyze your async http request first, and then the UI component.
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0 • Off Topic Insightful Disagree Dislike Like AwesomeThe method loadImages is caleld when the view loads.
-(void)loadImages{
self.photosArray = [[NSMutableArray alloc] initWithObjects:
@\"http://solar-center.stanford.edu/SID/images/earth.gif\",
@\"http://freeimagesarchive.com/data/media/27/3_space.jpg\",
@\"http://solar-center.stanford.edu/SID/images/earth.gif\",
@\"http://freeimagesarchive.com/data/media/27/3_space.jpg\",
@\"http://solar-center.stanford.edu/SID/images/earth.gif\",
@\"http://freeimagesarchive.com/data/media/27/3_space.jpg\",
@\"http://solar-center.stanford.edu/SID/images/earth.gif\",
@\"http://freeimagesarchive.com/data/media/27/3_space.jpg\",
nil];
[self runTimerAndDownloadImages];
}
-(void)runTimerAndDownloadImages{
for (int i = 0; i < [self.photosArray count]; i++) {
NSURLRequest *request = [[NSURLRequest alloc]initWithURL:[NSURL URLWithString:[self.photosArray objectAtIndex:i]] cachePolicy:NSURLRequestReturnCacheDataElseLoad timeoutInterval:30.0];
NSURLConnection *connection = [[NSURLConnection alloc]initWithRequest:request delegate:self];
if(connection){
self.imageData = [NSMutableData data];
}
}
}
- (void)connection:(NSURLConnection *)connection didReceiveResponse:(NSURLResponse *)response
{
[self.imageData setLength:0];
}
- (void)connection:(NSURLConnection *)connection didReceiveData:(NSData *)data
{
[self.imageData appendData:data];
}
- (void)connection:(NSURLConnection *)connection didFailWithError:(NSError *)error
{
NSLog(@\"Error!\");
}
- (void)connectionDidFinishLoading:(NSURLConnection *)connection
{
UIImage *downloadedImage = [[UIImage alloc] initWithData:self.imageData];
[[self.buttonsArray objectAtIndex:self.downloadedImageNumber] setImage:downloadedImage forState:UIControlStateNormal];
self.downloadedImageNumber++;
}
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0 • Off Topic Insightful Disagree Dislike Like Awesome- Spam
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