Try to call it in the viewDidAppear of the parentViewController.
Set a flag before showing the MPMoviePlayerViewController and check it in viewDidAppear. Then call your own method accordingly.
Hope this helps.
Pregunta
How can I call a custom -(void) in the parentViewController of a MPMoviePlayerViewCotroller when is is dismissed?
Solución
Try to call it in the viewDidAppear of the parentViewController.
Set a flag before showing the MPMoviePlayerViewController and check it in viewDidAppear. Then call your own method accordingly.
Hope this helps.