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 function that triggers the sound:

-(IBAction) playSound:(id)sender{

NSString *soundPath = [[NSBundle mainBundle]pathForResource:@"sound" ofType:@"wav"];
NSURL *fileURL = [[NSURL alloc] initFileURLWithPath:soundPath];

newPlayer = [[AVAudioPlayer alloc]initWithContentsOfURL:fileURL error:nil];
newPlayer.numberOfLoops = -1;
[newPlayer play];   
}

This is the function that stops the sound:

-(IBAction) stopSound{
if ([newPlayer isPlaying]) {
    [newPlayer stop];
}
[newPlayer release];
}

I first started out using the Touch Down event, which looped the sound seamlessly. At this point the stopSound worked together with the “Touch Up Inside” event.

The point, as I said, is the sound is supposed to be generated when the user drags his/her finger(s) across the screen. But when I tried to the tie the playSound function to the “Touch Drag Inside” 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 Drag Event.

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

Answer 1

My advice would be to create to generate a method that loops your audio clip (whatever duration, overlap, pausing, etc you want). Setup the method so that when you call it to play, it plays the way you want it to indefinitely.

The method might look like:

-(void) beginOrContinuePlayingAudioLoop:(BOOL)shouldPlay {

 //if touchesMoved called, shouldPlay will be YES
 //if touchesEnded called, shouldPlay will be NO

 if (shouldPlay == NO) {
 //cease playing
 currentlyPlaying = NO;
 }

if (currentlyPlaying == YES) {

return;

} else {

//begin playing audio
currentlyPlaying = YES;

 }
}

In your ViewController class, define a BOOL (currentlyPlaying) that indicates whether the audio loop is currently playing.

As opposed to using canned IBAction gesture recognizers, consider overriding the more generic touch responder calls, touchesMoved and touchesEnded on your view.

In touchesMoved, set your VC’s BOOL to YES and then fire your audio looping method to start playing. The “playing” method should always check and see if the audio is already playing, and only start playing

Also place a check in your method that returns/exits your method when the audio loop is already playing, this will avoid overlapping.

In touchesEnded, kill your audio via whatever method you choose, and reset the BOOL to NO.