Continue download in background

Question

I am creating an application wherein I am downloading some data from server. While going in background I want that connection should continue running so that data can be downloaded. I know there is method in appDelegate

- (void)applicationDidEnterBackground:(UIApplication *)application

which is called when application enters background. But as the connection is created in viewController, how can it be managed in appDelegate?
Also is/are there other way(s) this can be done? I have gone through this link but is there a something simple to implement?

that is the official way to do it, thre are no other ways as much as i know — Omar Abdelhafith, Jun 19 '12 at 12:26
you should check this link http://stackoverflow.com/questions/4579810/ios-application-background-downloading — swiftBoy, Jun 28 '12 at 10:58

score 15 · Accepted Answer · answered Jun 27 '12 at 01:32

One way to do some operations that continue in the background is to create a separate thread to do the downloading. Inside the thread, bracket your download operations between calls to beginBackgroundTaskWithExpirationHandler: and endBackgroundTask. You don't need to check to see whether you are running in the background or not, you just always call these two methods.

// Tell iOS this as a background task in case we get backgrounded
UIBackgroundTaskIdentifier taskId = [[UIApplication sharedApplication] 
          beginBackgroundTaskWithExpirationHandler:NULL];

//----------------------------------------------
// Perform your download operations here
//----------------------------------------------
ASIHTTPRequest *request = [ASIHTTPRequest requestWithURL:url];

// Tell iOS that we are done with stuff that needed to keep going even if backgrounded    
[[UIApplication sharedApplication] endBackgroundTask:taskId];

You can set ASIHttpRequest property : [request setShouldContinueWhenAppEntersBackground:YES]; — HelloWorld, Dec 08 '12 at 08:03
Thank you so much!!! Please correct me if I'm wrong: To conclude, there's almost no difference between running the task in background or foreground. Both would execute with this code. Yet 2 differences come to mind: 1. **if** your background task is too long, then maybe you would get terminated before finishing it! 2. It's better to `endBackgroundTask:taskId` so you'd save extra battery. — mfaani, Jul 19 '17 at 18:45

bennythemink · Answer 2 · 2012-06-19T12:40:27.250

3

[edit] Sorry I was incorrect, as was pointed out in the comments you can extend the time limit you have to perform operations once/before your app goes into the background. Here is Apple's Official Documentation

edited Jun 19 '12 at 12:40

answered Jun 19 '12 at 12:30

bennythemink

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This is not true, you can execute a [Finite-Length task](http://developer.apple.com/library/ios/#DOCUMENTATION/iPhone/Conceptual/iPhoneOSProgrammingGuide/ManagingYourApplicationsFlow/ManagingYourApplicationsFlow.html#//apple_ref/doc/uid/TP40007072-CH4-SW28) in the background for a maximum of 10 min. – rckoenes Jun 19 '12 at 12:31
@rckoenes you are indeed correct, my apologies. I will edit my answer. Thanks for the information :) – bennythemink Jun 19 '12 at 12:37
Still not true, you can call [`beginBackgroundTaskWithExpirationHandler:`](http://developer.apple.com/library/ios/#DOCUMENTATION/UIKit/Reference/UIApplication_Class/Reference/Reference.html#//apple_ref/occ/instm/UIApplication/beginBackgroundTaskWithExpirationHandler:) before executing the Finite-Length task. You do not need to perform the operations once you go in the background. You can start the task before your app get pushed to background. – rckoenes Jun 19 '12 at 12:43

score 1 · Answer 3 · answered Jun 26 '12 at 12:15

1

I don't know how you handle your data downloading exactly. But you can take a look at ASIHTTPRequest. It is very simple and straightforward, and works with ARC if you set the compiler flags to -fno-objc-arc. With this you only have to use

ASIHTTPRequest *request = [ASIHTTPRequest requestWithURL:url];
[request setShouldContinueWhenAppEntersBackground:YES]; //For iOS 4.0 and up

And that works.

Here you can see how ASIHTTPRequest works

Hope it helps!

answered Jun 26 '12 at 12:15

Thermometer

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ASIHTTPRequest is not actively developed anymore... as per message [here](http://allseeing-i.com/ASIHTTPRequest/). Just saying. – zero0cool Jun 28 '12 at 15:49
True, but it still works like a charm. I haven't found any good alternatives with as much functionality as ASIHTTPRequest. – Thermometer Jun 29 '12 at 12:51

Continue download in background

3 Answers3

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