NSURLConnection, tableview GUI hangs - iphone

Question

I am showing the images in the tableview using NSData dataWithContentsOfURL method but when i scroll the tableview GUI gets hanged.so after searching over the forum i found that i can try with NSUrlConnection method. so i tried but i cant implement it successfully.
Please find my code below...
kindly help me out that how i can correctly done it..
// Customize the appearance of table view cells.
- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath
{
static NSString *CellIdentifier = #"Cell";
UITableViewCell *cell = [tableView dequeueReusableCellWithIdentifier:CellIdentifier];
if (cell == nil)
{
cell = [[[UITableViewCell alloc] initWithFrame:CGRectZero reuseIdentifier:#"DataIdentifier"] autorelease];
cell.selectionStyle = UITableViewCellSelectionStyleNone;
cell.backgroundColor = [UIColor colorWithRed:230.0/255.0 green:249.0/255.0 blue:230.0/255.0 alpha:2.0];
cell.accessoryType = UITableViewCellAccessoryDisclosureIndicator;
profileName = [appDelegate.arrCommunityUserList objectAtIndex:indexPath.row];
NSString *imgName = [profileName.user_image stringByTrimmingCharactersInSet: [NSCharacterSet whitespaceAndNewlineCharacterSet]];
NSString *strValue = [NSString stringWithFormat:#"%d", profileName.userID];
if (tableView == myTableView)
{
cellRectangle = CGRectMake(15, 2, 75, 75 );
NSString *myurl = [NSString stringWithFormat: #"%#pics/photos/%#/%#",ConstantImgURL, strValue,imgName];
NSURL *url = [NSURL URLWithString: myurl];
imageView = [[UIImageView alloc] initWithFrame: cellRectangle];
NSURLRequest *request = [[NSURLRequest alloc] initWithURL:[NSURL URLWithString:myurl]];
[NSURLConnection connectionWithRequest:request delegate:self];
// create the connection with the request
// and start loading the data
NSURLConnection *theConnection =[[NSURLConnection alloc] initWithRequest:
request delegate:self];
if (theConnection)
{
receivedData = [[NSMutableData data] retain];
}
[cell.contentView addSubview:imageView];
}
}
return cell;
}
// did receive response
- ( void )connection:( NSURLConnection * )connection didReceiveResponse:( NSURLResponse * )response
//--------------------------------------------------------------------------------------------------
{
NSLog(#"Received response: %#", response);
}
// get recieved data
- ( void )connection:( NSURLConnection * )connection didReceiveData:( NSData * )data
//----------------------------------------------------------------------------------
{
// NSLog(#"Connection received data, retain count: %d", [connection retainCount]);
[receivedData appendData:data];
}
// finished loading
- ( void )connectionDidFinishLoading:( NSURLConnection * )connection
//-------------------------------------------------------------------
{
// Set appIcon and clear temporary data/image
UIImage *image = [[UIImage alloc] initWithData:receivedData];
imageView.image = image;
}
// connection failed with error
- ( void )connection:( NSURLConnection * )connection didFailWithError:( NSError * )connError
//---------------------------------------------------------------------------------------
{
// NSLog(#"Error receiving response: %#", connError);
[connection release];
[receivedData release];
}

Answer 1

dataWithContentsOfURL is a synchronous network request. That means that where your code is called it will wait until the request finishes before moving on to the next instruction. Synchronous networking is bad. Really bad. It only really ever works in testing.
What you should be doing, is firing off asynchronous requests for these images. The reason why your code above is horrendously slow is that every single time that the tableView asks its dataSource delegate for cellForRowAtIndexPath:; your code fires off a network request synchronously - which means the cell won't be returned until the network request for the image is finished.
Instead, what you should be doing is either loading all the images asynchronously when the tableView is requested. Here's a good example which uses tags to identify them as they return. This is not easy in the whole context of what you're doing; so perhaps you might want to start all the NSURLConnections when the tableView is shown, return 0 for numberOfSectionsInTableView until the connections finish, then call reloadData on the tableView when they're all finished (and make numberOfSectionsInTableView now return the right number of rows to display).

Answer 2

Start using ASI library: http://allseeing-i.com/ASIHTTPRequest/How-to-use
The sooner the better.

Answer 3

I think this might solve your Problem... http://www.markj.net/iphone-asynchronous-table-image/