Update views while being touched - iphone

Question

I am having an app where I load images in a UITableView. Each row has an image view.
I download images from URL and assign it to UIImageView. The problem here is that the image views are not updating if I was dragging the table view. It only updates when I release the finger.
Another problem is that I have a label in all cells that shows a counter which is incremented using a timer. Timer action is also not getting called when my finger is on the table view.
How do I do the updates in both these cases?
May be this is a very basic question. But I have no clue.
Thanks everyone!
EDIT: I have noticed that -connection:didReceiveResponse: method is not getting called when the view is being touched.
EDIT 2: I tried adding run loop with NSURLConnection. My method looks like this.
- (void)start {
NSMutableURLRequest* request = [[NSMutableURLRequest alloc] initWithURL:self.imageURL cachePolicy:NSURLRequestReturnCacheDataElseLoad timeoutInterval:self.timeoutInterval];
[request setValue:#"gzip" forHTTPHeaderField:#"Accept-Encoding"];
_connection = [[NSURLConnection alloc] initWithRequest:request delegate:self startImmediately:YES];
NSPort* port = [NSPort port];
NSRunLoop* rl = [NSRunLoop currentRunLoop]; // Get the runloop
[rl addPort:port forMode:NSRunLoopCommonModes];
[_connection scheduleInRunLoop:rl forMode:NSRunLoopCommonModes];
[_connection start];
[rl run];
}
This loads the images even when I am touching on the view. But the table view is scrolling very slowly. Its not even scrolling. It only moves when I drag. No movement after I release the finger.

Answer 1

Problem 1
The solution is to use downloading mechanism that doesn't get blocked while you drag the table view. SDWebImage is an asynchronous image downloader with cache support with an UIImageView category. This will let your image view to be updated even if you are dragging your table. I have faced a the same issue in my project where i used SDWebImage. Just a call like this will do.
[cell.imageView setImageWithURL:[NSURL URLWithString:#"http://www.domain.com/path/to/image.jpg"]
placeholderImage:[UIImage imageNamed:#"placeholder.png"]];
Problem 2
If its scheduledTimer will not get called while the main thread is tracking touches. Do something like this. Just create a timer and add to loop
NSTimer* timer = [NSTimer timerWithTimeInterval:1.0f target:self selector:#selector(updateLabel:) userInfo:nil repeats:YES];
[[NSRunLoop mainRunLoop] addTimer:timer forMode:NSRunLoopCommonModes];
this will not interrupt your timer.

Answer 2

this might be some helpful to you because you downloading images for displaying in UItableViewCells here i am giving you the example of the anything in background without blocking UI there you can get good tutorial link.they have mentioned enough good way same thing.go through this link
And Rest of the thing could be solved with the help of as Meera j Pai mentioned in his Answer.

Answer 3

I solved the problem with both NSConnection & NSTimer using the answers given by #Amar & #Meera J Pai, by using NSRunLoop.
I have changed my connection code to be like this.
_connection = [[NSURLConnection alloc] initWithRequest:request delegate:self startImmediately:NO]
[_connection scheduleInRunLoop:[NSRunLoop currentRunLoop] forMode:NSRunLoopCommonModes];
[_connection start];
It worked great!
Thanks everyone.