Why is it not possible to use the MPMoviePlayerCon

问题:

In MonoTouch, we ran into this problem with the Movie Player sample in that it would only play the video once, but would not play it a second time.

I am asking this question to post an answer, since it has been hitting various folks.

回答1:

MPMoviePlayerController is a singleton underneath the hood. If you have not properly release'd (ObjC) or Dispose()'d (MonoTouch) and you create a second instance, it will either not play, or play audio only.

Additionally if you subscribe to MPMoviePlayerScalingModeDidChangeNotification or MPMoviePlayerPlaybackDidFinishNotification or MPMoviePlayerContentPreloadDidFinishNotification, be warned that the posted NSNotification takes a reference to the MPMoviePlayerController as well, so if you keep it around, you will have a reference the player.

Although Mono's Garbage Collector will eventually kick-in, this is a case where deterministic termination is wanted (you want the reference gone now, not gone when the GC decides to perform a collection).

This is why you want to call the Dispose () method on the controller, and the Dispose() method on the notification.

For example:

// Deterministic termination, do not wait for the GC
if (moviePlayer != null){
    moviePlayer.Dispose ()
    moviePlayer = null;
}

If you were listening to notifications, call Dispose in your notification handler at the end, to release the reference that it keeps to your MPMoviePlayerController for example:

var center = NSNotificationCenter.DefaultCenter;
center.AddObserver (
    "MPMoviePlayerPlaybackDidFinishNotification"),
    (notify) => { Console.WriteLine ("Done!"); notify.Dispose (); });

回答2:

Can't see your code Nir and I don't have edit privileges so here it is again:

The secret lays in the endPlay with setting the: moviePlayer.initialPlaybackTime = -1; before releasing it. Try it out : :)

-(void)playMovie:(NSString *)urlString{ movieURL = [NSURL URLWithString:urlString];          
moviePlayer = [[MPMoviePlayerController alloc] initWithContentURL:movieURL];    
moviePlayer.initialPlaybackTime = 0; 
//Register to receive a notification when the movie has finished playing. 
[[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(endPlay:) name:MPMoviePlayerPlaybackDidFinishNotification object:moviePlayer];

moviePlayer.scalingMode = MPMovieScalingModeAspectFit; 
moviePlayer.movieControlMode = MPMovieControlModeDefault;
moviePlayer.backgroundColor = [UIColor blackColor];

[moviePlayer play];

}

-(void)endPlay: (NSNotification*)notification{
 [[NSNotificationCenter defaultCenter] removeObserver:self name:MPMoviePlayerPlaybackDidFinishNotification object:moviePlayer]; 
moviePlayer.initialPlaybackTime = -1; 
[moviePlayer stop]; 
[moviePlayer release]; 
} 

回答3:

The secret lays in the endPlay with setting the: moviePlayer.initialPlaybackTime = -1; before releasing it. Try it out : :)

-(void)playMovie:(NSString *)urlString{
    movieURL = [NSURL URLWithString:urlString]; 
    moviePlayer = [[MPMoviePlayerController alloc] initWithContentURL:movieURL];
    moviePlayer.initialPlaybackTime = 0;
    //Register to receive a notification when the movie has finished playing. 
    [[NSNotificationCenter defaultCenter] addObserver:self
                                             selector:@selector(endPlay:) 
                                                 name:MPMoviePlayerPlaybackDidFinishNotification 
                                               object:moviePlayer];

    moviePlayer.scalingMode = MPMovieScalingModeAspectFit; 
    moviePlayer.movieControlMode = MPMovieControlModeDefault;
    moviePlayer.backgroundColor = [UIColor blackColor];

    [moviePlayer play];

}

-(void)endPlay: (NSNotification*)notification{
    [[NSNotificationCenter defaultCenter] removeObserver:self name:MPMoviePlayerPlaybackDidFinishNotification object:moviePlayer];
    moviePlayer.initialPlaybackTime = -1;
    [moviePlayer stop];
    [moviePlayer release];
}