[iOS]使用MPMoviePlayerViewController來播放mp4，在iOS 6上無法順利播放問題解決方法。

在ios5的版本中，使用以下函式就可以順利播放mp4，但是這個函式在ios6卻會crash掉，最後終於找到在ios5與ios6可以使用的方法，詳情請參考該網址

原本在ios5上的寫法如下：(ios6將無法使用)

- (void)openMP4:(NSString *)s_url

{

    NSURL *fileURL = [NSURL URLWithString:s_url];

    [player.moviePlayer setControlStyle:MPMovieControlStyleFullscreen];

    [player.moviePlayer setFullscreen:NO];

    player = [[MPMoviePlayerViewController alloc] initWithContentURL:fileURL];

    //弹出播放器窗口

    [self  presentMoviePlayerViewControllerAnimated:player ];

    [player.moviePlayer setMovieSourceType:MPMovieSourceTypeFile];

    [player.moviePlayer prepareToPlay];

    [self.view addSubview:player.view];

    //播放

    [player.moviePlayer play];

    //增加一個觀察者

    [[NSNotificationCenter defaultCenter] addObserver:self

                                             selector:@selector(moviePlayBackDidFinish:)

                                                 name:MPMoviePlayerPlaybackDidFinishNotification

                                               object:nil];

}

- (void) moviePlayBackDidFinish:(NSNotification*) aNotification {

    //移除觀察者

    [[NSNotificationCenter     defaultCenter] removeObserver:self

                                                        name:MPMoviePlayerPlaybackDidFinishNotification

                                                      object:nil];

    //播放器消失

    [player dismissMoviePlayerViewControllerAnimated];

    player=NULL;

}

相容ios5、ios6的寫法如下（來源）：

- (void)openMP4:(NSString*)s_url
{

    // Initialize the movie player view controller with a video URL string

    NSURL *fileURL = [NSURL URLWithString:s_url];

    

    MPMoviePlayerViewController *playerVC = [[MPMoviePlayerViewController alloc] initWithContentURL:fileURL];

    

    // Remove the movie player view controller from the "playback did finish" notification observers

    [[NSNotificationCenter defaultCenter] removeObserver:playerVC

                                                    name:MPMoviePlayerPlaybackDidFinishNotification
                                                  object:playerVC.moviePlayer];

    

    // Register this class as an observer instead

    [[NSNotificationCenter defaultCenter] addObserver:self

                                             selector:@selector(movieFinishedCallback:)
                                                 name:MPMoviePlayerPlaybackDidFinishNotification
                                               object:playerVC.moviePlayer];

    

    // Set the modal transition style of your choice

    playerVC.modalTransitionStyle = UIModalTransitionStyleCrossDissolve;

    

    // Present the movie player view controller

    [self presentModalViewController:playerVC animated:YES];

    

    // Start playback

    [playerVC.moviePlayer prepareToPlay];
    [playerVC.moviePlayer play];
}
- (void)movieFinishedCallback:(NSNotification*)aNotification
{

    // Obtain the reason why the movie playback finished

    NSNumber *finishReason = [[aNotification userInfo] objectForKey:MPMoviePlayerPlaybackDidFinishReasonUserInfoKey];

    

    // Dismiss the view controller ONLY when the reason is not "playback ended"

    if ([finishReason intValue] != MPMovieFinishReasonPlaybackEnded)

    {
        MPMoviePlayerController *moviePlayer = [aNotification object];

        

        // Remove this class from the observers

        [[NSNotificationCenter defaultCenter] removeObserver:self

                                                        name:MPMoviePlayerPlaybackDidFinishNotification
                                                      object:moviePlayer];

        

        // Dismiss the view controller

        [self dismissModalViewControllerAnimated:YES];

    }
}