UI Hang in offline mode - ios

Question

Does any body know what I need to check if app freezes after some time ? I mean, I can see the app in the iPhone screen but no view responds.
I did some google and i found that, i've blocked the main thread somehow.
But my question is how to identify which method causes blocking of main thread ? is there any way to identify ?
I using XMPP for chat and core data for storing and retrieving the messages.I connect the app with XMPP Server in app delegate class.But i don't know how XMPP Delegate call again and again. According to me core data doing its work fine but in the offline mode XMPP try to disconnect and until it does not complete its task it freeze the app for some time and then works fine in the offline mode.
But I am not sure what is the culprit.I am not able to find the issue.
And i tried the pause button too when it freeze but in the left window i am not able to find which method make the app freeze.
Here is code which i am using
(UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath
{
static NSString *cellIdentifier = #"IMChatMessageCell";
CMMessageArchiving_Message_CoreDataObject *msgInfo = (CMMessageArchiving_Message_CoreDataObject *)[[self messageFetchResultController] objectAtIndexPath:indexPath];
IMPromos *promo = nil;
if (msgInfo.promo_Object)
{
promo = msgInfo.promo_Object;
////NSLog(#"%#", promo);
}
else
{
promo = [IMDataHandler fetchPromoForPromoID:msgInfo.promo_id];
msgInfo.promo_Object = promo;
}
if (msgInfo.mediaThumbnailPath)
return [self mediaMessageCell:tableView indexPath:indexPath messageInfo: msgInfo];
IMChatMessageCell chatMessageCell = (IMChatMessageCell)[tableView dequeueReusableCellWithIdentifier:cellIdentifier];
if (chatMessageCell == nil)
{
NSArray *objects = [[NSBundle mainBundle] loadNibNamed:cellIdentifier owner:nil options:nil];
for (NSObject *obj in objects)
{
if ([obj isKindOfClass:[IMChatMessageCell class]])
{
chatMessageCell = (IMChatMessageCell *)obj;
break;
}
}
}
int imageWith;
NSString *message = [msgInfo body];
if (NO == msgInfo.isOutgoing)// left aligned
{
// Just set the textfield here ///
NSString* promoImage = [[IMUtils getImageFolderPath] stringByAppendingPathComponent: [chatMessageCell.cellPromo.promo_image lastPathComponent]];
//NSLog(#"%#",promoImage);
UIImage *image = [UIImage imageWithContentsOfFile:promoImage];
if (image)
{
chatMessageCell.userImageView.image = image;
if(!promo.promo_message.length)
{
chatMessageCell.userImageView.frame = CGRectIntegral(CGRectMake(padding, 15, image.size.width,image.size.height));
bubbleItemOrigin=USER_IMAGE_Y_POS_WITHOUT_HEADER;
if(!promo.promo_link.length)
bubbleItemOrigin-=5;
}
else
{
chatMessageCell.userImageView.frame = CGRectIntegral(CGRectMake(padding, USER_IMAGE_Y_POS, image.size.width, image.size.height));
bubbleItemOrigin=USER_IMAGE_Y_POS;
}
}
return chatMessageCell;
}
(void)viewWillAppear:(BOOL)animated
{
[self scrollToBottom];
[super viewWillAppear:animated];
[self refreshTitleView];
messagesFetchResultController.delegate = self;
messageTextField.font = [IMUtils appFontWithSize:font_size];
}
I am using this code.
When i am running the app without network then it freeze
and something like this printing into logs
and XMPP'S delegate get called.