Question

I’m trying to do an app where a short sound sample is supposed to be played while the person using the app is dragging his/her finger(s) across the screen. When the finger(s) are lifted away from the screen – the sound will stop.

This is the current function that triggers the sound (I’ve tried various methods):

-(BOOL)ccTouchBegan:(UITouch *)touch withEvent:(UIEvent *)event{

NSLog(@"Ja, den börjar...");
return YES; 
}

-(void)ccTouchMoved:(NSSet *)touch withEvent:(UIEvent *)event{

    soundFile = [[CDAudioManager sharedManager] audioSourceForChannel:kASC_Right];
    [soundFile load:@"sound.wav"];
    soundFile.backgroundMusic = NO;
    soundSourceForFile:@"sound.wav"]retain];
}

This is the function that stops the sound:

-(void)ccTouchEnded:(UITouch *)touch withEvent:(UIEvent *)event{
    [soundFile stop]; 
}

I first started out using the ccTouchBegan (Just to get some kind of sound working), which looped the sound seamlessly. At this point the ccTouchEnded worked together with the “Touch Up Inside” event.

The point, as I said, is the the sound is supposed to be played when the user drags his/her finger(s) across the screen. But when I tried to the tie the playSound function to the “ccTouchMoved” the sound loops repeatedly over itself, instead of one at the time, making it hell to use. The stopSound function doesn’t work after i changed to the ccTouchMoved.

I tried to use NSTimer to create some kind of way to handle the loops, but without any success.

I started this project with the regular iOS SDK, and found my limitations when i found out i wasn’t able to handle pitch & gain manipulation without Cocos2d.

I got everything working in the regular SDK by wrapping it in a if-statement:

if(![mySound isPlaying]{
    [mySound play];
}

This, as I said, worked perfectly fine in the regular SDK, but not now when I’m using Cocos2d.

Answer 1

ccTouchMoved will be called continuously as the finger moves along the screen. The problem you are having here is that each time this is called you are loading a new sound file and they are overlapping because they are newly created individual objects. You only have a reference to the final sound you load (which is what soundFile is pointing at) and you aren’t freeing up the memory either.

Example:

(as you drag your finger)

LoadedSoundA created and starts playing
soundfile points to LoadedSoundA
// finger moves
LoadedSoundB created and starts playing
soundfile points to LoadedSoundB
// finger moves
LoadedSoundC created and starts playing
soundfile points to LoadedSoundC
... etc

the only sound you have a pointer to at the moment is the last created sound, since you reassign soundfile each time. So you can only ‘stop’ the sound you created last.

You are also leaking a lot of memory since you are retaining all of these sounds and never releasing them.

I would suggest a different tactic:

In touchesBegan you should load the sound and have it play on loop and record the time of the touch into a class level iVar.

Now, in TouchesMoved you should get the time of the current touch and see if it is close enough to the time you recorded. If it is within say, 0.5 seconds then just update the recorded timestamp and continue; However, if it has been too long since the last touch you stop the sound that is playing.

This way you have a seamless sound being played, it is only created once and you maintain your ownership of it.

Hope this helps