beginBackgroundTaskWithExpirationHandler

Question

I am making an application where audio will play in the background. In the following code, bgTask is undeclared. What kind of object should bgTask be?

- (void)applicationDidEnterBackground:(UIApplication *)application 
{
    UIApplication  *app = [UIApplication sharedApplication];
    bgTask = [app beginBackgroundTaskWithExpirationHandler:^{ 
        [app endBackgroundTask:bgTask]; 
        bgTask = UIBackgroundTaskInvalid;
    }];

    dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0), ^{});

    [app endBackgroundTask:bgTask]; 
    bgTask = UIBackgroundTaskInvalid;
}

please format your code in the right way. – Pavan Oct 06 '10 at 09:36 — Pavan, Oct 06 '10 at 09:36

score 17 · Accepted Answer · edited Aug 09 '13 at 13:13

17

You need to declare bgTask before you assign:

UIBackgroundTaskIdentifier bgTask = 0;

edited Aug 09 '13 at 13:13

Dev

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answered Oct 06 '10 at 09:42

willcodejavaforfood

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10

thanks. I want to spank myself every time I read one of these vague docs written by Apple (~90% of their docs). They should hire people who know how to write docs. – Duck Aug 25 '11 at 17:00
25

You want to spank yourself..? – Andy May 03 '12 at 13:24
@willcodejavaforfood I have tried this code with a timer but timer stops after round 10 minutes how can I continue it in a long time – Johnykutty Jun 05 '12 at 09:26
12

Just to clarify, it should be `UIBackgroundTaskIdentifier bgTask = 0;` since it is a `NSUInteger`. – Alexandre OS Aug 23 '12 at 12:35

score 10 · Answer 2 · answered Aug 05 '13 at 18:43

10

I cannot comment on previous answers, however to initialize UIBackgroundTaskIdentifier you should not set it to nil or 0. You should set it to:

UIBackgroundTaskInvalid

In the documentation UIBackgroundTaskInvalid says it should be used to initialize variables or to check for errors.

answered Aug 05 '13 at 18:43

Bontarest

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`UIBackgroundTaskInvalid = 0x0000000000000000`. Same thing. – duci9y Jan 11 '14 at 10:58
6

@duci9y believe me, you don't want magic numbers in your code. Stick to constants provided by API. – pronebird May 13 '14 at 11:22

score 2 · Answer 3 · answered Nov 25 '13 at 05:15

2

You are using the bgTask in the block so you have to declare it like this..

__block UIBackgroundTaskIdentifier bgTask = 0;

__block will allow this variable to use in the block method. And its have double underscore.

answered Nov 25 '13 at 05:15

Dilip Manek

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beginBackgroundTaskWithExpirationHandler

3 Answers3

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