iPhone OS 4 Multitasking - Playing Audio In background

Question

I am trying to use iPhone OS 4.0's multitasking capability. I tried to play audio in the background with no luck. I added UIBackgroundModes property in info.plist and mentioned requires audio to play in background. Also I added the code for playing the audio. `

NSURL *url = [NSURL fileURLWithPath:[[NSBundle mainBundle] pathForResource:@"someday" ofType:@"mp3"]]; 
AVAudioPlayer *audioPlayer = [[AVAudioPlayer alloc] initWithContentsOfURL:url error:nil];
[audioPlayer play];

`. The audio starts playing once i click on button in the app. But when I shut the app it stops. How can I make it play in the background?

Thanks, Tony

Answer 1

It sounds like you didn't set up your Audio Session correctly. From http://developer.apple.com/iphone/library/documentation/AudioVideo/Conceptual/MultimediaPG/UsingAudio/UsingAudio.html :

For example, when using the default audio session, audio in your application stops when the Auto-Lock period times out and the screen locks. If you want to ensure that playback continues with the screen locked, include the following lines in your application’s initialization code:

NSError *setCategoryErr = nil;
NSError *activationErr  = nil;
[[AVAudioSession sharedInstance] setCategory: AVAudioSessionCategoryPlayback error:&setCategoryErr];
[[AVAudioSession sharedInstance] setActive:YES error:&activationErr];

The AVAudioSessionCategoryPlayback category ensures that playback continues when the screen locks. Activating the audio session puts the specified category into effect.