Why does my audio play before the Sprite Kit scene transition? - ios

Question

In this code, Audio is a class where all things concerning AVAudioPlayer are handled. Currently there is some music playing. I want to have this fade out completely in 1 second and then play another song. Simultaneously, I want a new scene to appear. So I want the new song to start right as the transition (also lasting 1 second) ends. However, I find myself always waiting for the music to stop, before the scene transition starts. I've tried many ways, with and without selectors, with and without the various sleep functions, but without any luck. I've also tried to use stopMusic instead of transitionMusic and then use playMusic: in the new scene, but I always find myself waiting for stopMusic to finish before the transition starts.
Here's a part of the first scene, which is run if a certain button on the screen is pressed:
Audio *musicPlayer = [[Audio alloc] init];
NewScene *newScene = [NewScene sceneWithSize:self.size];
SKTransition *reveal = [SKTransition pushWithDirection:SKTransitionDirectionLeft duration:1.0];
reveal.pausesOutgoingScene = NO;
reveal.pausesIncomingScene = NO;
[self.view presentScene:newScene transition:reveal];
[musicPlayer transitionMusic:#"NewSong"];
The method transitionMusic: is as follows:
-(void)transitionMusic:(NSString *)fileName {
[self performSelectorOnMainThread:#selector(stopMusic) withObject:nil waitUntilDone:YES];
[self playMusic:fileName];
}
And stopMusic and playMusic: are:
-(void)stopMusic {
while(BGM.volume > 0.05) {
[BGM setVolume:(BGM.volume - 0.05)];
[NSThread sleepForTimeInterval:0.05];
}
[BGM stop];
}
-(void)playMusic:(NSString *)fileName {
NSURL * backgroundMusicURL = [[NSBundle mainBundle] URLForResource:[NSString stringWithFormat:#"%#",fileName] withExtension:#"caf"];
BGM = [[AVAudioPlayer alloc] initWithContentsOfURL:backgroundMusicURL error:nil];
[BGM setNumberOfLoops:-1];
[BGM setVolume:1.0];
[BGM prepareToPlay];
[BGM play];
}
Also, BGM is a static audioplayer declared in Audio.h. Can anyone point out what I'm doing wrong?

Answer 1

Your musicPlayer player object is dependent on your old scene. You need to create a singleton to handle your transition music independently from one scene to another.
BoxesOfBabies.com has a good tutorial on how to set up a singleton and use it to Control Music Across Multiple SKScene.
EDIT:
In your SKScene:
#import "MySingleton"
#implementation MainScene
{
MySingleton *_mySingleton;
}
In your init method:
_mySingleton = [MySingleton sharedInstance];
To start playing audio in any of your scenes:
[_mySingleton startPlayingSong1];
or
[_mySingleton startPlayingSong2];
whatever methods you have in your singleton.