Try this,
-(void)itemDidFinishPlaying {
[self displayContent: pageContent];
[[NSNotificationCenter defaultCenter] removeObserver:self name:AVPlayerItemDidPlayToEndTimeNotification object:playerItem];
}
It may work for you.
EDIT1:
Remove the notification observer every-time before you set the new one.Try the below scenario.It will ensure, remove the previous observer(even it doesn't exist no problem) and adds the new one.
// Subscribe to the AVPlayerItem's DidPlayToEndTime notification.
[[NSNotificationCenter defaultCenter] removeObserver:self name:AVPlayerItemDidPlayToEndTimeNotification object:playerItem];
[[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(itemDidFinishPlaying) name:AVPlayerItemDidPlayToEndTimeNotification object:playerItem];