为什么不能多次使用MPMoviePlayerController？

问题描述

在MonoTouch中，我们遇到了电影播放器​​样本的问题，因为它只会播放一次视频，但不会再播放一次。

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.

我问这个问题是为了发布答案，因为它已经打到了各种各样的人。

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

推荐答案

MPMoviePlayerController是引擎盖下的单身人士。如果您没有正确释放（ObjC）或Dispose（）'d（MonoTouch）并且您创建了第二个实例，它将无法播放或仅播放音频。

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.

此外，如果您订阅MPMoviePlayerScalingModeDidChangeNotification或MPMoviePlayerPlaybackDidFinishNotification或MPMoviePlayerContentPreloadDidFinishNotification，请注意已发布的NSNotification也会引用MPMoviePlayerController，因此如果您保留它，您将有一个引用播放器。

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.

虽然Mono的垃圾收集器最终会启动，但这是一个需要确定性终止的情况（你希望引用现在，当GC决定执行集合）。

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).

这就是你想要在控制器上调用Dispose（）方法，以及在通知上调用Dispose（）方法的原因。

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

例如：

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

如果您正在收听通知，请在通知处理程序中调用Dispose ，例如发布它保存到MPMoviePlayerController的引用：

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 (); });

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