Pause and resume is not working properly in AFNetwoking ios - ios

Question

I am using AFNetworking for downloading files having size between 1 to 4 gbs,.
Currently while downloading such a huge files I pause the current download when app enters in background state and resume when it gets active.
But what happens wrong in my case is that, first time while downloading when I minimize the app I pause it and when I again maximize app after 20 to 30 mins I resume it and download continues from where it was left paused last time. But it works only first time, second time when I again minimize the app with same download it gets paused and when I again maximizes it , it stuck at the same point showing some wrong values for progress and current transfer speed and it never moves forward or never continues current download.
Strange behaviour??
I have tried both old and new (2.0) versions but no luck.
Can you guess what is happening wrong in my case?
Or
Please suggest me some good alternatives to using AFNetworking.
UPDATE
Method called to download file
-(void) downloadTracksFromProgramArray:(NSArray*) programs
{
if (programs.count == 0) {
return;
}
queue = [[NSOperationQueue alloc] init];
[queue setMaxConcurrentOperationCount:1];
queueSize = 0;
urlString = [programs objectAtIndex:0];
NSString *filename = [urlString lastPathComponent];
// 11-09-12
// remove query string from aws
NSString *string1 = [NSHomeDirectory() stringByAppendingPathComponent:[NSString stringWithFormat:#"Documents/%#",[filename lastPathComponent]]] ;
// remove query string from aws
NSArray *jaysarray = [string1 componentsSeparatedByString:#"?"];
NSString *downloadPath1 = [NSString stringWithFormat:#"%#",[jaysarray objectAtIndex:0]];
extract_file_path_after_download = downloadPath1;
NSLog(#"%#",[jaysarray objectAtIndex:0]);
// NSLog(#"%#",[jaysarray objectAtIndex:1]);
current_downloading_file_path = [downloadPath1 copy];
NSLog(#"download url %#",[NSURL URLWithString:urlString]);
NSURLRequest *request = [NSURLRequest requestWithURL:[NSURL URLWithString:urlString]];
operation = [[AFHTTPRequestOperation alloc] initWithRequest:request];
operation.outputStream = [NSOutputStream outputStreamToFileAtPath:downloadPath1 append:NO];
//handle successful completion of each track download
[operation setCompletionBlockWithSuccess:^(AFHTTPRequestOperation *operation, id responseObject) {
NSLog(#"Successfully downloaded file to %#", downloadPath1);
//if ([[queue operations] count] == 0) {
NSNotification *success = [NSNotification notificationWithName:#"AudioDone" object:[NSNumber numberWithBool: YES]];
[[NSNotificationCenter defaultCenter] postNotification:success];
queueSize = 0;
//} else {
//send total track info
//get total queue size by the first success and add 1 back
if (queueSize ==0) {
queueSize = [[queue operations] count] +1.0;
}
float progress = (float)(queueSize-[[queue operations] count])/queueSize;
NSNumber * totProgress = [NSNumber numberWithFloat:progress];
NSLog(#"Total Progress: %#", totProgress);
current_downloading_file_path = #"";
//Commented by rakesh biradar - becoz #"TotalProgress" notification method does not do anything(memory).
//NSNotification * totalProgressNotification = [NSNotification notificationWithName:#"TotalProgress"
// object:totProgress];
//[[NSNotificationCenter defaultCenter] postNotification:totalProgressNotification];
//}
NSLog(#"QueueCount: %d", [[queue operations] count]); //[[self sharedQueue] operationCount]);
} failure:^(AFHTTPRequestOperation *operation, NSError *error) {
//deletes the partial downloaded file from document folder
if(([current_downloading_file_path length] > 0) && [[NSFileManager defaultManager] fileExistsAtPath:current_downloading_file_path])
[[NSFileManager defaultManager] removeItemAtPath:current_downloading_file_path error:nil];
current_downloading_file_path = #"";
NSLog(#"Error: %#", error);
}];
//Send progress notification
[operation setDownloadProgressBlock:^(NSUInteger bytesWritten, long long totalBytesWritten, long long totalBytesExpectedToWrite) {
//NSLog(#"Sent %lld of %lld bytes, %#", totalBytesWritten, totalBytesExpectedToWrite, path);
float percentDone = ((float)((int)totalBytesWritten) / (float)((int)totalBytesExpectedToWrite));
//NSLog(#"Percent: %f", percentDone);
NSDictionary *userInfo = [NSDictionary dictionaryWithObjects: [NSArray arrayWithObjects:filename, [NSNumber numberWithFloat: percentDone],[NSNumber numberWithLongLong:totalBytesWritten],[NSNumber numberWithLongLong:totalBytesExpectedToWrite],[NSNumber numberWithUnsignedInteger:bytesWritten],nil]
forKeys:[NSArray arrayWithObjects:#"message", #"percent",#"totalBytesWritten",#"totalBytesExpectedToWrite",#"bytesWritten", nil]];
NSNotification * progress = [NSNotification notificationWithName:#"DownloadingAudio" object:nil userInfo:userInfo];
[[NSNotificationCenter defaultCenter] postNotification:progress];
}];
[queue addOperation:operation];
//[self enqueueHTTPRequestOperation:operation];
//NSLog(#"Operation Queue: %#", [self sharedQueue]);
}
Method when app goes in background
- (void)applicationWillResignActive:(UIApplication *)application {
// Sent when the application is about to move from active to inactive state. This can occur for certain types of temporary interruptions (such as an incoming phone call or SMS message) or when the user quits the application and it begins the transition to the background state.
// Use this method to pause ongoing tasks, disable timers, and throttle down OpenGL ES frame rates. Games should use this method to pause the game.
if (operation)
{
NSLog(#"%#",operation);
//[self saveCustomObject:operation];
[operation pause];
}
}
Method called when app becomes active
- (void)applicationDidBecomeActive:(UIApplication *)application {
// Restart any tasks that were paused (or not yet started) while the application was inactive. If the application was previously in the background, optionally refresh the user interface.
// Handle the user leaving the app while the Facebook login dialog is being shown
// For example: when the user presses the iOS "home" button while the login dialog is active
if (operation)
{
//operation = [self loadCustomObjectWithKey:#"myEncodedObjectKey"];
NSLog(#"%#",operation);
[operation resume];
}
[FBAppCall handleDidBecomeActive];
}