当我发布mpmovieplayercontroller对象并在需要时再次分配时，为什么应用程序会崩溃？

Question

我正在使用MPMoviePlayerController。我正在初始化控制器对象，当用户退出或播放完成时，发送通知并释放控制器对象。再次单击按钮播放视频时，应用程序崩溃。但是当我释放一切正常后，我将控制器对象设置为nil，应用程序不会崩溃。请解释

-(void)playVideo { 
    MPMoviePlayerController *moviePlayerController = [[MPMoviePlayerController alloc] initWithContentURL:fileURL] ;
     self.mpMoviePlayer = moviePlayerController; 
    [moviePlayerController release]; 
    [[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(moviePlaybackComplete:) name:MPMoviePlayerPlaybackDidFinishNotification object:nil];
 }

 -(void)moviePlaybackComplete:(NSNotification *)notification {
                 if(self.mpMoviePlayer) { 
                [self.mpMoviePlayer stop];
                  [mpMoviePlayer.view removeFromSuperview];
                 [mpMoviePlayer release];
                 mpMoviePlayer = nil;//If i dont set it to nil here the app crashes the second time video is played 
    }