iphone开发怎么后台播放音频

NSError *myErr = nil;

AVAudioSession *audioSession = [AVAudioSession sharedInstance];

BOOL bAudioInputAvailable = [audioSession inputIsAvailable];

?

if?(bAudioInputAvailable)

{?

? ?[audioSession?setCategory:AVAudioSessionCategoryPlayAndRecord?error:&myErr];

}? ??

else

{

? ?[audioSession setCategory:AVAudioSessionCategoryPlayback error:&myErr];

}