Playing movie in iPhone 3.1 and 4.0

In iPhone 3.1 I used the following code to play a movie:

moviePlayer = [[MPMoviePlayerController alloc] initWithContentURL:url];
moviePlayer.movieControlMode = MPMovieControlModeDefault;
moviePlayer.backgroundColor = [UIColor blackColor];
[[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(playbackDidFinish:) name:MPMoviePlayerPlaybackDidFinishNotification object:moviePlayer];  
[moviePlayer play]; 

For some reason this does not work anymore in iPhone 4.0 (go Apple!). How should I play a movie in iPhone 4.0 开发者_如何学Pythonwhile retaining backward-compatibility with iPhone 3.1?