NSNotificationCenter notification fired twice on swipe - ios

Question

I am building an app with AVPlayer that will play songs from an api.
When a song ends, next song will be played. For this I am using the following code:
- (void)viewDidLoad
{
[[NSNotificationCenter defaultCenter] addObserver:self
selector:#selector(playbackFinished:)
name:AVPlayerItemDidPlayToEndTimeNotification
object:[_audioPlayer currentItem]];
}
-(void)playbackFinished:(NSNotification *)notification {
// flagSkip = NO;
NSLog(#"## %# ", NSStringFromSelector(_cmd));
// if(flagSkip == NO)
[[DataSingleton sharedMySingleton] nextTrack];
// else
// flagSkip = NO;
}
On Swipe gesture, next song will be played.
For this, am removing the notification observer and adding it again as follows:
- (IBAction)skipButtonPressed:(id)sender
{
[[DataSingleton sharedMySingleton] nextTrack];
[[NSNotificationCenter defaultCenter] removeObserver:self name:AVPlayerItemDidPlayToEndTimeNotification object:[_audioPlayer currentItem]];
[[NSNotificationCenter defaultCenter] addObserver:self
selector:#selector(playbackFinished:)
name:AVPlayerItemDidPlayToEndTimeNotification
object:[_audioPlayer currentItem]];
}else{
//
}
}
But when I swipe, sometimes the notification method gets called.
Where am I getting wrong? How do I solve this?
Edit to include [[DataSingleton sharedMySingleton] nextTrack]
-(void)nextTrack{
NSDictionary *prevTrackInfo;
if (currentIndex == -1){
// We're at the start of a refilled list, so previousTrack should be
// the only thing in the cache dir. Clean it up.
dispatch_queue_t removeFilesQueue;
NSLog(#"## %# removeFilesQueue", NSStringFromSelector(_cmd));
removeFilesQueue = dispatch_queue_create("com.zombieprocess.removeFilesQueue", DISPATCH_QUEUE_SERIAL);
dispatch_sync(removeFilesQueue, ^{
// Code goes here
NSError *error = nil;
[fileMgr removeItemAtPath:[self getFeedBandsCacheDir] error:&error];
[fileMgr createDirectoryAtPath:[self getFeedBandsCacheDir] withIntermediateDirectories:YES attributes:nil error:nil];
});
//dispatch_release(removeFilesQueue);
} else{
if (trackInfo){
prevTrackInfo = trackInfo;
}else{
NSLog(#"nextTrack, attempting to store prevTrackInfo, no trackInfo for currentIndex: %d", currentIndex);
}
}
currentIndex += 1;
// We should not have this, but just in case
if (currentIndex >= self.feedEntries.count) {
// We are at the end. Get the feed again.
NSLog(#"## %# currentIndex >= self.feedEntries.count", NSStringFromSelector(_cmd));
if (self.feedEntries.count == 0) {
[self loadFeed];
return;
}
currentIndex = 0; // This will loop it back to the beginning
// [self loadFeed];
// return;
}
trackInfo = [self.feedEntries objectAtIndex:currentIndex];
[self dispatchPlayNotification];
if (prevTrackInfo && [self isTrackCached:prevTrackInfo] && prevTrackInfo != trackInfo && feedEntries.count > [self numberOfSongsToCache]){
NSLog(#"nextTrack, deleting cached copy: %#", [[prevTrackInfo objectForKey:#"file_url"] lastPathComponent]);
[self deleteCachedTrack:prevTrackInfo completionBlock:^{
[self fillDownloadQueue];
}];
} else {
[self fillDownloadQueue];
}
}

Answer 1

I guess you've already switched the next song. So you can't remove notification observer with [_audioPlayer currentItem], because it is already changed.
Update 1.
Try to replace 1st and 2nd lines:
[[NSNotificationCenter defaultCenter] removeObserver:self name:AVPlayerItemDidPlayToEndTimeNotification object:[_audioPlayer currentItem]];
[[DataSingleton sharedMySingleton] nextTrack];
[[NSNotificationCenter defaultCenter] addObserver:self selector:#selector(playbackFinished:) name:AVPlayerItemDidPlayToEndTimeNotification object:[_audioPlayer currentItem]];

Answer 2

Instead of removing the notification listener, I would read the current state on the player inside the method (void)playbackFinished:(NSNotification *)notification.
For example:
- (IBAction)skipButtonPressed:(id)sender
{
didSkipSong = YES;
[[DataSingleton sharedMySingleton] nextTrack];
}
And in -(void)playbackFinished:(NSNotification *)notification
-(void)playbackFinished:(NSNotification *)notification {
if(didSkipSong){
didSkipSong = NO;
return;
}
[[DataSingleton sharedMySingleton] nextTrack];
}