beginBackgroundTaskWithExpirationHandler never gets called - iphone

Question

I have an app that plays audio in the background. I'm trying to use beginBackgroundTaskWithExpirationHandler to skip to the next track when the current track is finished.
Here is the code that is called when the playback state changes. It never logs the "beginBG called" even though other code in the same method implements successfully in the background.
UIApplication *app = [UIApplication sharedApplication];
bgTask = [app beginBackgroundTaskWithExpirationHandler:^{
[self ffwButtonPressed:ffwButton];
NSLog(#"beginBG called");
[app endBackgroundTask:bgTask];
bgTask = UIBackgroundTaskInvalid;
}];
ffwButtonPressed invokes a few different methods to change the track. When that is complete...
UIApplication *app = [UIApplication sharedApplication];
if (bgTask != UIBackgroundTaskInvalid) {
[app endBackgroundTask:bgTask];
bgTask = UIBackgroundTaskInvalid;
NSLog(#"end bgTask");
Edit: Declaration
UIBackgroundTaskIdentifier bgTask;
Edit: In ViewDidLoad
bgTask = 0;

Answer 1

You are actually misunderstanding the function
-(UIBackgroundTaskIdentifier)beginBackgroundTaskWithExpirationHandler:(void (^)(void))handler
The block argument called "handler" is what will happen when the background task expire (10min).
To get your code running you need to put your code out of the expiration handler:
UIApplication *app = [UIApplication sharedApplication];
bgTask = [app beginBackgroundTaskWithExpirationHandler:^{
bgTask = UIBackgroundTaskInvalid;
};
[self ffwButtonPressed:ffwButton];
NSLog(#"beginBG called");
[app endBackgroundTask:bgTask];
Here is a link to the documentation

Answer 2

I ended up not needing beginBackgroundTaskWithExpirationHandler at all. This line solved my problem...
[[UIApplication sharedApplication] beginReceivingRemoteControlEvents];

Answer 3

Does your App have a permission to run in the background as an Audio App? (need to put the right mode in your Info.plist)
See Apple's docs

Answer 4

beginBackgroundTaskWithExpirationHandler handler only get called when timer runout which is fairly large value. Real task as mentioned by Tomsum above should not be part part of block. Also remember to call endBackgroundTask: at end if backGroundTaskID != UIBackgroundTaskInvalid and only thing need to be done in block is setting back task variable = UIBackgroundTaskInvalid

Answer 5

Swift Version:
var backgroundTask: UIBackgroundTaskIdentifier? = 0
backgroundTask = UIApplication.shared.beginBackgroundTask(withName: "backgroundTask", expirationHandler: {() -> Void in
backgroundTask = UIBackgroundTaskInvalid
})
// Perform actions in background
YOUR_CODE_GOES_HERE (e.g. fetch requests, etc.)
UIApplication.shared.endBackgroundTask(backgroundTask!)

Answer 6

there can be a little modify, we should add endBackgroundTask in expiration handler:
IApplication *app = [UIApplication sharedApplication];
bgTask = [app beginBackgroundTaskWithExpirationHandler:^{
[app endBackgroundTask:bgTask];
bgTask = UIBackgroundTaskInvalid;
};
[self ffwButtonPressed:ffwButton];
NSLog(#"beginBG called");
[app endBackgroundTask:bgTask];

Answer 7

Is this all your code? Maybe the bgTask variable is not initialized, You need to declare bgTask before you assign. Try this -
UIBackgroundTaskIdentifier bgTask = nil;